Fix clippy lints

61 files changed, 460 insertions, 508 deletions

diff --git a/compiler/rustc_borrowck/src/lib.rs b/compiler/rustc_borrowck/src/lib.rs
index 6ffa0095e4b..43032ae81cb 100644
--- a/compiler/rustc_borrowck/src/lib.rs
+++ b/compiler/rustc_borrowck/src/lib.rs
@@ -277,26 +277,26 @@ fn do_mir_borrowck<'a, 'tcx>(
 
     let regioncx = Rc::new(regioncx);
 
-    let flow_borrows = Borrows::new(tcx, &body, &regioncx, &borrow_set)
-        .into_engine(tcx, &body)
+    let flow_borrows = Borrows::new(tcx, body, &regioncx, &borrow_set)
+        .into_engine(tcx, body)
         .pass_name("borrowck")
         .iterate_to_fixpoint();
-    let flow_uninits = MaybeUninitializedPlaces::new(tcx, &body, &mdpe)
-        .into_engine(tcx, &body)
+    let flow_uninits = MaybeUninitializedPlaces::new(tcx, body, &mdpe)
+        .into_engine(tcx, body)
         .pass_name("borrowck")
         .iterate_to_fixpoint();
-    let flow_ever_inits = EverInitializedPlaces::new(tcx, &body, &mdpe)
-        .into_engine(tcx, &body)
+    let flow_ever_inits = EverInitializedPlaces::new(tcx, body, &mdpe)
+        .into_engine(tcx, body)
         .pass_name("borrowck")
         .iterate_to_fixpoint();
 
-    let movable_generator = match tcx.hir().get(id) {
+    let movable_generator = !matches!(
+        tcx.hir().get(id),
         Node::Expr(&hir::Expr {
             kind: hir::ExprKind::Closure(.., Some(hir::Movability::Static)),
             ..
-        }) => false,
-        _ => true,
-    };
+        })
+    );
 
     for (idx, move_data_results) in promoted_errors {
         let promoted_body = &promoted[idx];
@@ -374,8 +374,8 @@ fn do_mir_borrowck<'a, 'tcx>(
     mbcx.report_move_errors(move_errors);
 
     rustc_mir_dataflow::visit_results(
-        &body,
-        traversal::reverse_postorder(&body).map(|(bb, _)| bb),
+        body,
+        traversal::reverse_postorder(body).map(|(bb, _)| bb),
         &results,
         &mut mbcx,
     );
diff --git a/compiler/rustc_codegen_llvm/src/abi.rs b/compiler/rustc_codegen_llvm/src/abi.rs
index 1a0a3a0c340..dca9c1f04d3 100644
--- a/compiler/rustc_codegen_llvm/src/abi.rs
+++ b/compiler/rustc_codegen_llvm/src/abi.rs
@@ -526,7 +526,7 @@ impl<'tcx> FnAbiLlvmExt<'tcx> for FnAbi<'tcx, Ty<'tcx>> {
         };
         match self.ret.mode {
             PassMode::Direct(ref attrs) => {
-                attrs.apply_attrs_to_callsite(llvm::AttributePlace::ReturnValue, &bx.cx, callsite);
+                attrs.apply_attrs_to_callsite(llvm::AttributePlace::ReturnValue, bx.cx, callsite);
             }
             PassMode::Indirect { ref attrs, extra_attrs: _, on_stack } => {
                 assert!(!on_stack);
diff --git a/compiler/rustc_codegen_llvm/src/asm.rs b/compiler/rustc_codegen_llvm/src/asm.rs
index 9690ad8b246..341a8882416 100644
--- a/compiler/rustc_codegen_llvm/src/asm.rs
+++ b/compiler/rustc_codegen_llvm/src/asm.rs
@@ -105,7 +105,7 @@ impl AsmBuilderMethods<'tcx> for Builder<'a, 'll, 'tcx> {
         let r = r.unwrap();
 
         // Again, based on how many outputs we have
-        let outputs = ia.outputs.iter().zip(&outputs).filter(|&(ref o, _)| !o.is_indirect);
+        let outputs = ia.outputs.iter().zip(&outputs).filter(|&(o, _)| !o.is_indirect);
         for (i, (_, &place)) in outputs.enumerate() {
             let v = if num_outputs == 1 { r } else { self.extract_value(r, i as u64) };
             OperandValue::Immediate(v).store(self, place);
@@ -331,7 +331,7 @@ impl AsmBuilderMethods<'tcx> for Builder<'a, 'll, 'tcx> {
         let output_type = match &output_types[..] {
             [] => self.type_void(),
             [ty] => ty,
-            tys => self.type_struct(&tys, false),
+            tys => self.type_struct(tys, false),
         };
         let dialect = match asm_arch {
             InlineAsmArch::X86 | InlineAsmArch::X86_64
diff --git a/compiler/rustc_codegen_llvm/src/back/lto.rs b/compiler/rustc_codegen_llvm/src/back/lto.rs
index 99b30264d09..e2b33509b40 100644
--- a/compiler/rustc_codegen_llvm/src/back/lto.rs
+++ b/compiler/rustc_codegen_llvm/src/back/lto.rs
@@ -109,7 +109,7 @@ fn prepare_lto(
                     .extend(exported_symbols[&cnum].iter().filter_map(symbol_filter));
             }
 
-            let archive = ArchiveRO::open(&path).expect("wanted an rlib");
+            let archive = ArchiveRO::open(path).expect("wanted an rlib");
             let obj_files = archive
                 .iter()
                 .filter_map(|child| child.ok().and_then(|c| c.name().map(|name| (name, c))))
@@ -316,14 +316,14 @@ fn fat_lto(
                 .generic_activity_with_arg("LLVM_fat_lto_link_module", format!("{:?}", name));
             info!("linking {:?}", name);
             let data = bc_decoded.data();
-            linker.add(&data).map_err(|()| {
+            linker.add(data).map_err(|()| {
                 let msg = format!("failed to load bc of {:?}", name);
-                write::llvm_err(&diag_handler, &msg)
+                write::llvm_err(diag_handler, &msg)
             })?;
             serialized_bitcode.push(bc_decoded);
         }
         drop(linker);
-        save_temp_bitcode(&cgcx, &module, "lto.input");
+        save_temp_bitcode(cgcx, &module, "lto.input");
 
         // Fat LTO also suffers from the invalid DWARF issue similar to Thin LTO.
         // Here we rewrite all `DICompileUnit` pointers if there is only one `DICompileUnit`.
@@ -347,14 +347,14 @@ fn fat_lto(
                 ptr as *const *const libc::c_char,
                 symbols_below_threshold.len() as libc::size_t,
             );
-            save_temp_bitcode(&cgcx, &module, "lto.after-restriction");
+            save_temp_bitcode(cgcx, &module, "lto.after-restriction");
         }
 
         if cgcx.no_landing_pads {
             unsafe {
                 llvm::LLVMRustMarkAllFunctionsNounwind(llmod);
             }
-            save_temp_bitcode(&cgcx, &module, "lto.after-nounwind");
+            save_temp_bitcode(cgcx, &module, "lto.after-nounwind");
         }
     }
 
@@ -498,7 +498,7 @@ fn thin_lto(
             symbols_below_threshold.as_ptr(),
             symbols_below_threshold.len() as u32,
         )
-        .ok_or_else(|| write::llvm_err(&diag_handler, "failed to prepare thin LTO context"))?;
+        .ok_or_else(|| write::llvm_err(diag_handler, "failed to prepare thin LTO context"))?;
 
         let data = ThinData(data);
 
@@ -572,7 +572,7 @@ fn thin_lto(
         if let Some(path) = key_map_path {
             if let Err(err) = curr_key_map.save_to_file(&path) {
                 let msg = format!("Error while writing ThinLTO key data: {}", err);
-                return Err(write::llvm_err(&diag_handler, &msg));
+                return Err(write::llvm_err(diag_handler, &msg));
             }
         }
 
@@ -744,8 +744,7 @@ pub unsafe fn optimize_thin_module(
     // crates but for locally codegened modules we may be able to reuse
     // that LLVM Context and Module.
     let llcx = llvm::LLVMRustContextCreate(cgcx.fewer_names);
-    let llmod_raw =
-        parse_module(llcx, &module_name, thin_module.data(), &diag_handler)? as *const _;
+    let llmod_raw = parse_module(llcx, module_name, thin_module.data(), &diag_handler)? as *const _;
     let module = ModuleCodegen {
         module_llvm: ModuleLlvm { llmod_raw, llcx, tm },
         name: thin_module.name().to_string(),
@@ -754,7 +753,7 @@ pub unsafe fn optimize_thin_module(
     {
         let target = &*module.module_llvm.tm;
         let llmod = module.module_llvm.llmod();
-        save_temp_bitcode(&cgcx, &module, "thin-lto-input");
+        save_temp_bitcode(cgcx, &module, "thin-lto-input");
 
         // Before we do much else find the "main" `DICompileUnit` that we'll be
         // using below. If we find more than one though then rustc has changed
@@ -775,7 +774,7 @@ pub unsafe fn optimize_thin_module(
                 .prof
                 .generic_activity_with_arg("LLVM_thin_lto_remove_landing_pads", thin_module.name());
             llvm::LLVMRustMarkAllFunctionsNounwind(llmod);
-            save_temp_bitcode(&cgcx, &module, "thin-lto-after-nounwind");
+            save_temp_bitcode(cgcx, &module, "thin-lto-after-nounwind");
         }
 
         // Up next comes the per-module local analyses that we do for Thin LTO.
@@ -947,7 +946,7 @@ pub fn parse_module<'a>(
         llvm::LLVMRustParseBitcodeForLTO(cx, data.as_ptr(), data.len(), name.as_ptr()).ok_or_else(
             || {
                 let msg = "failed to parse bitcode for LTO module";
-                write::llvm_err(&diag_handler, msg)
+                write::llvm_err(diag_handler, msg)
             },
         )
     }
diff --git a/compiler/rustc_codegen_llvm/src/back/write.rs b/compiler/rustc_codegen_llvm/src/back/write.rs
index 9b0e7526894..8856dc938ee 100644
--- a/compiler/rustc_codegen_llvm/src/back/write.rs
+++ b/compiler/rustc_codegen_llvm/src/back/write.rs
@@ -41,7 +41,7 @@ use std::sync::Arc;
 pub fn llvm_err(handler: &rustc_errors::Handler, msg: &str) -> FatalError {
     match llvm::last_error() {
         Some(err) => handler.fatal(&format!("{}: {}", msg, err)),
-        None => handler.fatal(&msg),
+        None => handler.fatal(msg),
     }
 }
 
@@ -96,7 +96,7 @@ pub fn create_target_machine(tcx: TyCtxt<'_>, mod_name: &str) -> &'static mut ll
         None
     };
     let config = TargetMachineFactoryConfig { split_dwarf_file };
-    target_machine_factory(&tcx.sess, tcx.backend_optimization_level(()))(config)
+    target_machine_factory(tcx.sess, tcx.backend_optimization_level(()))(config)
         .unwrap_or_else(|err| llvm_err(tcx.sess.diagnostic(), &err).raise())
 }
 
@@ -556,7 +556,7 @@ pub(crate) unsafe fn optimize(
                 let prepare_for_thin_lto = cgcx.lto == Lto::Thin
                     || cgcx.lto == Lto::ThinLocal
                     || (cgcx.lto != Lto::Fat && cgcx.opts.cg.linker_plugin_lto.enabled());
-                with_llvm_pmb(llmod, &config, opt_level, prepare_for_thin_lto, &mut |b| {
+                with_llvm_pmb(llmod, config, opt_level, prepare_for_thin_lto, &mut |b| {
                     llvm::LLVMRustAddLastExtensionPasses(
                         b,
                         extra_passes.as_ptr(),
@@ -658,9 +658,9 @@ pub(crate) fn link(
         let _timer =
             cgcx.prof.generic_activity_with_arg("LLVM_link_module", format!("{:?}", module.name));
         let buffer = ModuleBuffer::new(module.module_llvm.llmod());
-        linker.add(&buffer.data()).map_err(|()| {
+        linker.add(buffer.data()).map_err(|()| {
             let msg = format!("failed to serialize module {:?}", module.name);
-            llvm_err(&diag_handler, &msg)
+            llvm_err(diag_handler, &msg)
         })?;
     }
     drop(linker);
diff --git a/compiler/rustc_codegen_llvm/src/builder.rs b/compiler/rustc_codegen_llvm/src/builder.rs
index dab7d3eaa8c..9f7b8616d78 100644
--- a/compiler/rustc_codegen_llvm/src/builder.rs
+++ b/compiler/rustc_codegen_llvm/src/builder.rs
@@ -86,7 +86,7 @@ impl ty::layout::HasParamEnv<'tcx> for Builder<'_, '_, 'tcx> {
 impl HasTargetSpec for Builder<'_, '_, 'tcx> {
     #[inline]
     fn target_spec(&self) -> &Target {
-        &self.cx.target_spec()
+        self.cx.target_spec()
     }
 }
 
diff --git a/compiler/rustc_codegen_llvm/src/callee.rs b/compiler/rustc_codegen_llvm/src/callee.rs
index a96ba148a6c..5d68d2b77d4 100644
--- a/compiler/rustc_codegen_llvm/src/callee.rs
+++ b/compiler/rustc_codegen_llvm/src/callee.rs
@@ -44,7 +44,7 @@ pub fn get_fn(cx: &CodegenCx<'ll, 'tcx>, instance: Instance<'tcx>) -> &'ll Value
 
     let fn_abi = cx.fn_abi_of_instance(instance, ty::List::empty());
 
-    let llfn = if let Some(llfn) = cx.get_declared_value(&sym) {
+    let llfn = if let Some(llfn) = cx.get_declared_value(sym) {
         // Create a fn pointer with the new signature.
         let llptrty = fn_abi.ptr_to_llvm_type(cx);
 
@@ -79,7 +79,7 @@ pub fn get_fn(cx: &CodegenCx<'ll, 'tcx>, instance: Instance<'tcx>) -> &'ll Value
             llfn
         }
     } else {
-        let llfn = cx.declare_fn(&sym, &fn_abi);
+        let llfn = cx.declare_fn(sym, fn_abi);
         debug!("get_fn: not casting pointer!");
 
         attributes::from_fn_attrs(cx, llfn, instance);
diff --git a/compiler/rustc_codegen_llvm/src/consts.rs b/compiler/rustc_codegen_llvm/src/consts.rs
index ef3a90fdeca..1afa6f02836 100644
--- a/compiler/rustc_codegen_llvm/src/consts.rs
+++ b/compiler/rustc_codegen_llvm/src/consts.rs
@@ -178,7 +178,7 @@ fn check_and_apply_linkage(
         };
         unsafe {
             // Declare a symbol `foo` with the desired linkage.
-            let g1 = cx.declare_global(&sym, llty2);
+            let g1 = cx.declare_global(sym, llty2);
             llvm::LLVMRustSetLinkage(g1, base::linkage_to_llvm(linkage));
 
             // Declare an internal global `extern_with_linkage_foo` which
@@ -188,7 +188,7 @@ fn check_and_apply_linkage(
             // `extern_with_linkage_foo` will instead be initialized to
             // zero.
             let mut real_name = "_rust_extern_with_linkage_".to_string();
-            real_name.push_str(&sym);
+            real_name.push_str(sym);
             let g2 = cx.define_global(&real_name, llty).unwrap_or_else(|| {
                 cx.sess().span_fatal(
                     cx.tcx.def_span(span_def_id),
@@ -202,7 +202,7 @@ fn check_and_apply_linkage(
     } else {
         // Generate an external declaration.
         // FIXME(nagisa): investigate whether it can be changed into define_global
-        cx.declare_global(&sym, llty)
+        cx.declare_global(sym, llty)
     }
 }
 
@@ -234,7 +234,7 @@ impl CodegenCx<'ll, 'tcx> {
                 _ => self.define_private_global(self.val_ty(cv)),
             };
             llvm::LLVMSetInitializer(gv, cv);
-            set_global_alignment(&self, gv, align);
+            set_global_alignment(self, gv, align);
             llvm::SetUnnamedAddress(gv, llvm::UnnamedAddr::Global);
             gv
         }
@@ -279,7 +279,7 @@ impl CodegenCx<'ll, 'tcx> {
 
             g
         } else {
-            check_and_apply_linkage(&self, &fn_attrs, ty, sym, def_id)
+            check_and_apply_linkage(self, fn_attrs, ty, sym, def_id)
         };
 
         // Thread-local statics in some other crate need to *always* be linked
@@ -369,7 +369,7 @@ impl StaticMethods for CodegenCx<'ll, 'tcx> {
         unsafe {
             let attrs = self.tcx.codegen_fn_attrs(def_id);
 
-            let (v, alloc) = match codegen_static_initializer(&self, def_id) {
+            let (v, alloc) = match codegen_static_initializer(self, def_id) {
                 Ok(v) => v,
                 // Error has already been reported
                 Err(_) => return,
@@ -417,7 +417,7 @@ impl StaticMethods for CodegenCx<'ll, 'tcx> {
                 self.statics_to_rauw.borrow_mut().push((g, new_g));
                 new_g
             };
-            set_global_alignment(&self, g, self.align_of(ty));
+            set_global_alignment(self, g, self.align_of(ty));
             llvm::LLVMSetInitializer(g, v);
 
             if self.should_assume_dso_local(g, true) {
@@ -430,7 +430,7 @@ impl StaticMethods for CodegenCx<'ll, 'tcx> {
                 llvm::LLVMSetGlobalConstant(g, llvm::True);
             }
 
-            debuginfo::create_global_var_metadata(&self, def_id, g);
+            debuginfo::create_global_var_metadata(self, def_id, g);
 
             if attrs.flags.contains(CodegenFnAttrFlags::THREAD_LOCAL) {
                 llvm::set_thread_local_mode(g, self.tls_model);
@@ -518,7 +518,7 @@ impl StaticMethods for CodegenCx<'ll, 'tcx> {
                     );
                 }
             } else {
-                base::set_link_section(g, &attrs);
+                base::set_link_section(g, attrs);
             }
 
             if attrs.flags.contains(CodegenFnAttrFlags::USED) {
diff --git a/compiler/rustc_codegen_llvm/src/context.rs b/compiler/rustc_codegen_llvm/src/context.rs
index 7bdbec11d60..257a0ac89d8 100644
--- a/compiler/rustc_codegen_llvm/src/context.rs
+++ b/compiler/rustc_codegen_llvm/src/context.rs
@@ -363,7 +363,7 @@ impl<'ll, 'tcx> CodegenCx<'ll, 'tcx> {
 
     fn create_used_variable_impl(&self, name: &'static CStr, values: &[&'ll Value]) {
         let section = cstr!("llvm.metadata");
-        let array = self.const_array(&self.type_ptr_to(self.type_i8()), values);
+        let array = self.const_array(self.type_ptr_to(self.type_i8()), values);
 
         unsafe {
             let g = llvm::LLVMAddGlobal(self.llmod, self.val_ty(array), name.as_ptr());
@@ -447,7 +447,7 @@ impl MiscMethods<'tcx> for CodegenCx<'ll, 'tcx> {
     }
 
     fn sess(&self) -> &Session {
-        &self.tcx.sess
+        self.tcx.sess
     }
 
     fn check_overflow(&self) -> bool {
diff --git a/compiler/rustc_codegen_llvm/src/coverageinfo/mapgen.rs b/compiler/rustc_codegen_llvm/src/coverageinfo/mapgen.rs
index d2a2e739ff3..6830864ba04 100644
--- a/compiler/rustc_codegen_llvm/src/coverageinfo/mapgen.rs
+++ b/compiler/rustc_codegen_llvm/src/coverageinfo/mapgen.rs
@@ -73,7 +73,7 @@ pub fn finalize<'ll, 'tcx>(cx: &CodegenCx<'ll, 'tcx>) {
             mapgen.write_coverage_mapping(expressions, counter_regions, coverage_mapping_buffer);
         });
         debug_assert!(
-            coverage_mapping_buffer.len() > 0,
+            !coverage_mapping_buffer.is_empty(),
             "Every `FunctionCoverage` should have at least one counter"
         );
 
@@ -311,8 +311,7 @@ fn add_unused_functions<'ll, 'tcx>(cx: &CodegenCx<'ll, 'tcx>) {
     // for each region in it's MIR.
 
     // Convert the `HashSet` of `codegenned_def_ids` to a sortable vector, and sort them.
-    let mut sorted_codegenned_def_ids: Vec<DefId> =
-        codegenned_def_ids.iter().map(|def_id| *def_id).collect();
+    let mut sorted_codegenned_def_ids: Vec<DefId> = codegenned_def_ids.iter().copied().collect();
     sorted_codegenned_def_ids.sort_unstable();
 
     let mut first_covered_def_id_by_file: FxHashMap<Symbol, DefId> = FxHashMap::default();
diff --git a/compiler/rustc_codegen_llvm/src/coverageinfo/mod.rs b/compiler/rustc_codegen_llvm/src/coverageinfo/mod.rs
index 093aceda2b7..ef11e2972ea 100644
--- a/compiler/rustc_codegen_llvm/src/coverageinfo/mod.rs
+++ b/compiler/rustc_codegen_llvm/src/coverageinfo/mod.rs
@@ -199,8 +199,8 @@ fn declare_unused_fn(cx: &CodegenCx<'ll, 'tcx>, def_id: &DefId) -> Instance<'tcx
     );
 
     let llfn = cx.declare_fn(
-        &tcx.symbol_name(instance).name,
-        &cx.fn_abi_of_fn_ptr(
+        tcx.symbol_name(instance).name,
+        cx.fn_abi_of_fn_ptr(
             ty::Binder::dummy(tcx.mk_fn_sig(
                 iter::once(tcx.mk_unit()),
                 tcx.mk_unit(),
diff --git a/compiler/rustc_codegen_llvm/src/debuginfo/create_scope_map.rs b/compiler/rustc_codegen_llvm/src/debuginfo/create_scope_map.rs
index 1612922d439..58f8573a2ac 100644
--- a/compiler/rustc_codegen_llvm/src/debuginfo/create_scope_map.rs
+++ b/compiler/rustc_codegen_llvm/src/debuginfo/create_scope_map.rs
@@ -41,7 +41,7 @@ pub fn compute_mir_scopes(
     // Instantiate all scopes.
     for idx in 0..mir.source_scopes.len() {
         let scope = SourceScope::new(idx);
-        make_mir_scope(cx, instance, &mir, fn_dbg_scope, &has_variables, debug_context, scope);
+        make_mir_scope(cx, instance, mir, fn_dbg_scope, &has_variables, debug_context, scope);
     }
 }
 
@@ -94,7 +94,7 @@ fn make_mir_scope(
                 callee,
             );
             let callee_fn_abi = cx.fn_abi_of_instance(callee, ty::List::empty());
-            cx.dbg_scope_fn(callee, &callee_fn_abi, None)
+            cx.dbg_scope_fn(callee, callee_fn_abi, None)
         }
         None => unsafe {
             llvm::LLVMRustDIBuilderCreateLexicalBlock(
diff --git a/compiler/rustc_codegen_llvm/src/debuginfo/gdb.rs b/compiler/rustc_codegen_llvm/src/debuginfo/gdb.rs
index c33d35cc285..ae1f83d944f 100644
--- a/compiler/rustc_codegen_llvm/src/debuginfo/gdb.rs
+++ b/compiler/rustc_codegen_llvm/src/debuginfo/gdb.rs
@@ -59,10 +59,8 @@ pub fn get_or_insert_gdb_debug_scripts_section_global(cx: &CodegenCx<'ll, '_>) -
 }
 
 pub fn needs_gdb_debug_scripts_section(cx: &CodegenCx<'_, '_>) -> bool {
-    let omit_gdb_pretty_printer_section = cx
-        .tcx
-        .sess
-        .contains_name(&cx.tcx.hir().krate_attrs(), sym::omit_gdb_pretty_printer_section);
+    let omit_gdb_pretty_printer_section =
+        cx.tcx.sess.contains_name(cx.tcx.hir().krate_attrs(), sym::omit_gdb_pretty_printer_section);
 
     !omit_gdb_pretty_printer_section
         && cx.sess().opts.debuginfo != DebugInfo::None
diff --git a/compiler/rustc_codegen_llvm/src/debuginfo/metadata.rs b/compiler/rustc_codegen_llvm/src/debuginfo/metadata.rs
index 9272435a330..f6ec5e6395f 100644
--- a/compiler/rustc_codegen_llvm/src/debuginfo/metadata.rs
+++ b/compiler/rustc_codegen_llvm/src/debuginfo/metadata.rs
@@ -477,7 +477,7 @@ fn subroutine_type_metadata(
     let signature_metadata: Vec<_> = iter::once(
         // return type
         match signature.output().kind() {
-            ty::Tuple(ref tys) if tys.is_empty() => None,
+            ty::Tuple(tys) if tys.is_empty() => None,
             _ => Some(type_metadata(cx, signature.output(), span)),
         },
     )
@@ -647,7 +647,7 @@ pub fn type_metadata(cx: &CodegenCx<'ll, 'tcx>, t: Ty<'tcx>, usage_site_span: Sp
         ty::Never | ty::Bool | ty::Char | ty::Int(_) | ty::Uint(_) | ty::Float(_) => {
             MetadataCreationResult::new(basic_type_metadata(cx, t), false)
         }
-        ty::Tuple(ref elements) if elements.is_empty() => {
+        ty::Tuple(elements) if elements.is_empty() => {
             MetadataCreationResult::new(basic_type_metadata(cx, t), false)
         }
         ty::Array(typ, _) | ty::Slice(typ) => {
@@ -746,7 +746,7 @@ pub fn type_metadata(cx: &CodegenCx<'ll, 'tcx>, t: Ty<'tcx>, usage_site_span: Sp
                     .finalize(cx)
             }
         },
-        ty::Tuple(ref elements) => {
+        ty::Tuple(elements) => {
             let tys: Vec<_> = elements.iter().map(|k| k.expect_ty()).collect();
             prepare_tuple_metadata(cx, t, &tys, unique_type_id, usage_site_span, NO_SCOPE_METADATA)
                 .finalize(cx)
@@ -932,7 +932,7 @@ fn basic_type_metadata(cx: &CodegenCx<'ll, 'tcx>, t: Ty<'tcx>) -> &'ll DIType {
 
     let (name, encoding) = match t.kind() {
         ty::Never => ("!", DW_ATE_unsigned),
-        ty::Tuple(ref elements) if elements.is_empty() => ("()", DW_ATE_unsigned),
+        ty::Tuple(elements) if elements.is_empty() => ("()", DW_ATE_unsigned),
         ty::Bool => ("bool", DW_ATE_boolean),
         ty::Char => ("char", DW_ATE_unsigned_char),
         ty::Int(int_ty) if msvc_like_names => (int_ty.msvc_basic_name(), DW_ATE_signed),
@@ -1123,7 +1123,7 @@ pub fn compile_unit_metadata(
 
             let gcov_cu_info = [
                 path_to_mdstring(debug_context.llcontext, &output_filenames.with_extension("gcno")),
-                path_to_mdstring(debug_context.llcontext, &gcda_path),
+                path_to_mdstring(debug_context.llcontext, gcda_path),
                 cu_desc_metadata,
             ];
             let gcov_metadata = llvm::LLVMMDNodeInContext(
@@ -1963,17 +1963,13 @@ impl<'tcx> VariantInfo<'_, 'tcx> {
     }
 
     fn source_info(&self, cx: &CodegenCx<'ll, 'tcx>) -> Option<SourceInfo<'ll>> {
-        match self {
-            VariantInfo::Generator { def_id, variant_index, .. } => {
-                let span = cx.tcx.generator_layout(*def_id).unwrap().variant_source_info
-                    [*variant_index]
-                    .span;
-                if !span.is_dummy() {
-                    let loc = cx.lookup_debug_loc(span.lo());
-                    return Some(SourceInfo { file: file_metadata(cx, &loc.file), line: loc.line });
-                }
+        if let VariantInfo::Generator { def_id, variant_index, .. } = self {
+            let span =
+                cx.tcx.generator_layout(*def_id).unwrap().variant_source_info[*variant_index].span;
+            if !span.is_dummy() {
+                let loc = cx.lookup_debug_loc(span.lo());
+                return Some(SourceInfo { file: file_metadata(cx, &loc.file), line: loc.line });
             }
-            _ => {}
         }
         None
     }
@@ -1994,11 +1990,11 @@ fn describe_enum_variant(
         let unique_type_id = debug_context(cx)
             .type_map
             .borrow_mut()
-            .get_unique_type_id_of_enum_variant(cx, layout.ty, &variant_name);
+            .get_unique_type_id_of_enum_variant(cx, layout.ty, variant_name);
         create_struct_stub(
             cx,
             layout.ty,
-            &variant_name,
+            variant_name,
             unique_type_id,
             Some(containing_scope),
             DIFlags::FlagZero,
@@ -2385,7 +2381,7 @@ fn set_members_of_composite_type(
     {
         let mut composite_types_completed =
             debug_context(cx).composite_types_completed.borrow_mut();
-        if !composite_types_completed.insert(&composite_type_metadata) {
+        if !composite_types_completed.insert(composite_type_metadata) {
             bug!(
                 "debuginfo::set_members_of_composite_type() - \
                   Already completed forward declaration re-encountered."
diff --git a/compiler/rustc_codegen_llvm/src/debuginfo/mod.rs b/compiler/rustc_codegen_llvm/src/debuginfo/mod.rs
index fbaf8c8bdf6..894320a7982 100644
--- a/compiler/rustc_codegen_llvm/src/debuginfo/mod.rs
+++ b/compiler/rustc_codegen_llvm/src/debuginfo/mod.rs
@@ -328,7 +328,7 @@ impl DebugInfoMethods<'tcx> for CodegenCx<'ll, 'tcx> {
         // name if necessary.
         let generics = self.tcx().generics_of(enclosing_fn_def_id);
         let substs = instance.substs.truncate_to(self.tcx(), generics);
-        let template_parameters = get_template_parameters(self, &generics, substs, &mut name);
+        let template_parameters = get_template_parameters(self, generics, substs, &mut name);
 
         let linkage_name = &mangled_name_of_instance(self, instance).name;
         // Omit the linkage_name if it is the same as subprogram name.
@@ -559,7 +559,7 @@ impl DebugInfoMethods<'tcx> for CodegenCx<'ll, 'tcx> {
         scope_metadata: &'ll DIScope,
         file: &rustc_span::SourceFile,
     ) -> &'ll DILexicalBlock {
-        metadata::extend_scope_to_file(&self, scope_metadata, file)
+        metadata::extend_scope_to_file(self, scope_metadata, file)
     }
 
     fn debuginfo_finalize(&self) {
diff --git a/compiler/rustc_codegen_llvm/src/intrinsic.rs b/compiler/rustc_codegen_llvm/src/intrinsic.rs
index be55a0c868a..22dc8d101c8 100644
--- a/compiler/rustc_codegen_llvm/src/intrinsic.rs
+++ b/compiler/rustc_codegen_llvm/src/intrinsic.rs
@@ -71,7 +71,7 @@ fn get_simple_intrinsic(cx: &CodegenCx<'ll, '_>, name: Symbol) -> Option<(&'ll T
         sym::roundf64 => "llvm.round.f64",
         _ => return None,
     };
-    Some(cx.get_intrinsic(&llvm_name))
+    Some(cx.get_intrinsic(llvm_name))
 }
 
 impl IntrinsicCallMethods<'tcx> for Builder<'a, 'll, 'tcx> {
@@ -743,7 +743,7 @@ fn gen_fn<'ll, 'tcx>(
 ) -> (&'ll Type, &'ll Value) {
     let fn_abi = cx.fn_abi_of_fn_ptr(rust_fn_sig, ty::List::empty());
     let llty = fn_abi.llvm_type(cx);
-    let llfn = cx.declare_fn(name, &fn_abi);
+    let llfn = cx.declare_fn(name, fn_abi);
     cx.set_frame_pointer_type(llfn);
     cx.apply_target_cpu_attr(llfn);
     // FIXME(eddyb) find a nicer way to do this.
@@ -1159,7 +1159,7 @@ fn generic_simd_intrinsic(
             _ => return_error!("unrecognized intrinsic `{}`", name),
         };
         let llvm_name = &format!("llvm.{0}.v{1}{2}", intr_name, in_len, elem_ty_str);
-        let f = bx.declare_cfn(&llvm_name, llvm::UnnamedAddr::No, fn_ty);
+        let f = bx.declare_cfn(llvm_name, llvm::UnnamedAddr::No, fn_ty);
         let c =
             bx.call(fn_ty, f, &args.iter().map(|arg| arg.immediate()).collect::<Vec<_>>(), None);
         Ok(c)
@@ -1793,7 +1793,7 @@ unsupported {} from `{}` with element `{}` of size `{}` to `{}`"#,
         let vec_ty = bx.cx.type_vector(elem_ty, in_len as u64);
 
         let fn_ty = bx.type_func(&[vec_ty, vec_ty], vec_ty);
-        let f = bx.declare_cfn(&llvm_intrinsic, llvm::UnnamedAddr::No, fn_ty);
+        let f = bx.declare_cfn(llvm_intrinsic, llvm::UnnamedAddr::No, fn_ty);
         let v = bx.call(fn_ty, f, &[lhs, rhs], None);
         return Ok(v);
     }
diff --git a/compiler/rustc_codegen_llvm/src/lib.rs b/compiler/rustc_codegen_llvm/src/lib.rs
index c44cc656056..8f4d79e7147 100644
--- a/compiler/rustc_codegen_llvm/src/lib.rs
+++ b/compiler/rustc_codegen_llvm/src/lib.rs
@@ -339,7 +339,7 @@ impl ModuleLlvm {
         unsafe {
             let llcx = llvm::LLVMRustContextCreate(cgcx.fewer_names);
             let llmod_raw = back::lto::parse_module(llcx, name, buffer, handler)?;
-            let tm_factory_config = TargetMachineFactoryConfig::new(&cgcx, name.to_str().unwrap());
+            let tm_factory_config = TargetMachineFactoryConfig::new(cgcx, name.to_str().unwrap());
             let tm = match (cgcx.tm_factory)(tm_factory_config) {
                 Ok(m) => m,
                 Err(e) => {
diff --git a/compiler/rustc_codegen_llvm/src/llvm/ffi.rs b/compiler/rustc_codegen_llvm/src/llvm/ffi.rs
index d8c2a345fb0..436d906827b 100644
--- a/compiler/rustc_codegen_llvm/src/llvm/ffi.rs
+++ b/compiler/rustc_codegen_llvm/src/llvm/ffi.rs
@@ -789,7 +789,7 @@ pub mod coverageinfo {
                 start_line,
                 start_col,
                 end_line,
-                end_col: ((1 as u32) << 31) | end_col,
+                end_col: (1_u32 << 31) | end_col,
                 kind: RegionKind::GapRegion,
             }
         }
diff --git a/compiler/rustc_codegen_llvm/src/llvm_util.rs b/compiler/rustc_codegen_llvm/src/llvm_util.rs
index f9172e43773..c5deb11edd0 100644
--- a/compiler/rustc_codegen_llvm/src/llvm_util.rs
+++ b/compiler/rustc_codegen_llvm/src/llvm_util.rs
@@ -298,7 +298,7 @@ fn print_target_features(sess: &Session, tm: &llvm::TargetMachine) {
     for (feature, desc) in &target_features {
         println!("    {1:0$} - {2}.", max_feature_len, feature, desc);
     }
-    if target_features.len() == 0 {
+    if target_features.is_empty() {
         println!("    Target features listing is not supported by this LLVM version.");
     }
     println!("\nUse +feature to enable a feature, or -feature to disable it.");
diff --git a/compiler/rustc_codegen_llvm/src/mono_item.rs b/compiler/rustc_codegen_llvm/src/mono_item.rs
index b9022a391e6..88498cf47d8 100644
--- a/compiler/rustc_codegen_llvm/src/mono_item.rs
+++ b/compiler/rustc_codegen_llvm/src/mono_item.rs
@@ -53,10 +53,10 @@ impl PreDefineMethods<'tcx> for CodegenCx<'ll, 'tcx> {
         assert!(!instance.substs.needs_infer());
 
         let fn_abi = self.fn_abi_of_instance(instance, ty::List::empty());
-        let lldecl = self.declare_fn(symbol_name, &fn_abi);
+        let lldecl = self.declare_fn(symbol_name, fn_abi);
         unsafe { llvm::LLVMRustSetLinkage(lldecl, base::linkage_to_llvm(linkage)) };
         let attrs = self.tcx.codegen_fn_attrs(instance.def_id());
-        base::set_link_section(lldecl, &attrs);
+        base::set_link_section(lldecl, attrs);
         if linkage == Linkage::LinkOnceODR || linkage == Linkage::WeakODR {
             llvm::SetUniqueComdat(self.llmod, lldecl);
         }
@@ -145,10 +145,6 @@ impl CodegenCx<'ll, 'tcx> {
 
         // With pie relocation model calls of functions defined in the translation
         // unit can use copy relocations.
-        if self.tcx.sess.relocation_model() == RelocModel::Pie && !is_declaration {
-            return true;
-        }
-
-        return false;
+        self.tcx.sess.relocation_model() == RelocModel::Pie && !is_declaration
     }
 }
diff --git a/compiler/rustc_codegen_llvm/src/type_.rs b/compiler/rustc_codegen_llvm/src/type_.rs
index c7f4287e28e..2ae0a08f192 100644
--- a/compiler/rustc_codegen_llvm/src/type_.rs
+++ b/compiler/rustc_codegen_llvm/src/type_.rs
@@ -248,7 +248,7 @@ impl Type {
     }
 
     fn ptr_to(&self, address_space: AddressSpace) -> &Type {
-        unsafe { llvm::LLVMPointerType(&self, address_space.0) }
+        unsafe { llvm::LLVMPointerType(self, address_space.0) }
     }
 }
 
diff --git a/compiler/rustc_codegen_llvm/src/type_of.rs b/compiler/rustc_codegen_llvm/src/type_of.rs
index 9e03fc33ae0..f8c919ec2aa 100644
--- a/compiler/rustc_codegen_llvm/src/type_of.rs
+++ b/compiler/rustc_codegen_llvm/src/type_of.rs
@@ -232,7 +232,7 @@ impl<'tcx> LayoutLlvmExt<'tcx> for TyAndLayout<'tcx> {
                     cx.type_ptr_to(cx.layout_of(self.ty.boxed_ty()).llvm_type(cx))
                 }
                 ty::FnPtr(sig) => {
-                    cx.fn_ptr_backend_type(&cx.fn_abi_of_fn_ptr(sig, ty::List::empty()))
+                    cx.fn_ptr_backend_type(cx.fn_abi_of_fn_ptr(sig, ty::List::empty()))
                 }
                 _ => self.scalar_llvm_type_at(cx, scalar, Size::ZERO),
             };
@@ -245,7 +245,7 @@ impl<'tcx> LayoutLlvmExt<'tcx> for TyAndLayout<'tcx> {
             Variants::Single { index } => Some(index),
             _ => None,
         };
-        if let Some(ref llty) = cx.type_lowering.borrow().get(&(self.ty, variant_index)) {
+        if let Some(llty) = cx.type_lowering.borrow().get(&(self.ty, variant_index)) {
             return llty.lltype;
         }
 
@@ -270,10 +270,9 @@ impl<'tcx> LayoutLlvmExt<'tcx> for TyAndLayout<'tcx> {
         };
         debug!("--> mapped {:#?} to llty={:?}", self, llty);
 
-        cx.type_lowering.borrow_mut().insert(
-            (self.ty, variant_index),
-            TypeLowering { lltype: llty, field_remapping: field_remapping },
-        );
+        cx.type_lowering
+            .borrow_mut()
+            .insert((self.ty, variant_index), TypeLowering { lltype: llty, field_remapping });
 
         if let Some((llty, layout)) = defer {
             let (llfields, packed, new_field_remapping) = struct_llfields(cx, layout);
diff --git a/compiler/rustc_codegen_llvm/src/va_arg.rs b/compiler/rustc_codegen_llvm/src/va_arg.rs
index caafae6c267..591f659f11b 100644
--- a/compiler/rustc_codegen_llvm/src/va_arg.rs
+++ b/compiler/rustc_codegen_llvm/src/va_arg.rs
@@ -125,7 +125,7 @@ fn emit_aapcs_va_arg(
     // if the offset >= 0 then the value will be on the stack
     let mut reg_off_v = bx.load(bx.type_i32(), reg_off, offset_align);
     let use_stack = bx.icmp(IntPredicate::IntSGE, reg_off_v, zero);
-    bx.cond_br(use_stack, &on_stack.llbb(), &maybe_reg.llbb());
+    bx.cond_br(use_stack, on_stack.llbb(), maybe_reg.llbb());
 
     // The value at this point might be in a register, but there is a chance that
     // it could be on the stack so we have to update the offset and then check
@@ -142,7 +142,7 @@ fn emit_aapcs_va_arg(
     // Check to see if we have overflowed the registers as a result of this.
     // If we have then we need to use the stack for this value
     let use_stack = maybe_reg.icmp(IntPredicate::IntSGT, new_reg_off_v, zero);
-    maybe_reg.cond_br(use_stack, &on_stack.llbb(), &in_reg.llbb());
+    maybe_reg.cond_br(use_stack, on_stack.llbb(), in_reg.llbb());
 
     let top_type = bx.type_i8p();
     let top = in_reg.struct_gep(va_list_ty, va_list_addr, reg_top_index);
@@ -158,17 +158,17 @@ fn emit_aapcs_va_arg(
     let reg_type = layout.llvm_type(bx);
     let reg_addr = in_reg.bitcast(reg_addr, bx.cx.type_ptr_to(reg_type));
     let reg_value = in_reg.load(reg_type, reg_addr, layout.align.abi);
-    in_reg.br(&end.llbb());
+    in_reg.br(end.llbb());
 
     // On Stack block
     let stack_value =
         emit_ptr_va_arg(&mut on_stack, list, target_ty, false, Align::from_bytes(8).unwrap(), true);
-    on_stack.br(&end.llbb());
+    on_stack.br(end.llbb());
 
     let val = end.phi(
         layout.immediate_llvm_type(bx),
         &[reg_value, stack_value],
-        &[&in_reg.llbb(), &on_stack.llbb()],
+        &[in_reg.llbb(), on_stack.llbb()],
     );
 
     *bx = end;
diff --git a/compiler/rustc_driver/src/lib.rs b/compiler/rustc_driver/src/lib.rs
index 4c6a2baaef1..7fd7f6b1340 100644
--- a/compiler/rustc_driver/src/lib.rs
+++ b/compiler/rustc_driver/src/lib.rs
@@ -128,7 +128,7 @@ impl Callbacks for TimePassesCallbacks {
 }
 
 pub fn diagnostics_registry() -> Registry {
-    Registry::new(&rustc_error_codes::DIAGNOSTICS)
+    Registry::new(rustc_error_codes::DIAGNOSTICS)
 }
 
 /// This is the primary entry point for rustc.
@@ -265,8 +265,8 @@ fn run_compiler(
                         &***compiler.codegen_backend(),
                         compiler.session(),
                         None,
-                        &compiler.output_dir(),
-                        &compiler.output_file(),
+                        compiler.output_dir(),
+                        compiler.output_file(),
                     );
 
                     if should_stop == Compilation::Stop {
@@ -330,7 +330,7 @@ fn run_compiler(
                     let krate = queries.parse()?.take();
                     pretty::print_after_parsing(
                         sess,
-                        &compiler.input(),
+                        compiler.input(),
                         &krate,
                         *ppm,
                         compiler.output_file().as_ref().map(|p| &**p),
@@ -356,7 +356,7 @@ fn run_compiler(
 
                 // Lint plugins are registered; now we can process command line flags.
                 if sess.opts.describe_lints {
-                    describe_lints(&sess, &lint_store, true);
+                    describe_lints(sess, lint_store, true);
                     return early_exit();
                 }
             }
@@ -388,7 +388,7 @@ fn run_compiler(
                         save::process_crate(
                             tcx,
                             &crate_name,
-                            &compiler.input(),
+                            compiler.input(),
                             None,
                             DumpHandler::new(
                                 compiler.output_dir().as_ref().map(|p| &**p),
@@ -598,7 +598,7 @@ impl RustcDefaultCalls {
             if let Input::File(file) = compiler.input() {
                 // FIXME: #![crate_type] and #![crate_name] support not implemented yet
                 sess.init_crate_types(collect_crate_types(sess, &[]));
-                let outputs = compiler.build_output_filenames(&sess, &[]);
+                let outputs = compiler.build_output_filenames(sess, &[]);
                 let rlink_data = fs::read_to_string(file).unwrap_or_else(|err| {
                     sess.fatal(&format!("failed to read rlink file: {}", err));
                 });
@@ -606,7 +606,7 @@ impl RustcDefaultCalls {
                     json::decode(&rlink_data).unwrap_or_else(|err| {
                         sess.fatal(&format!("failed to decode rlink: {}", err));
                     });
-                let result = compiler.codegen_backend().link(&sess, codegen_results, &outputs);
+                let result = compiler.codegen_backend().link(sess, codegen_results, &outputs);
                 abort_on_err(result, sess);
             } else {
                 sess.fatal("rlink must be a file")
@@ -894,9 +894,9 @@ Available lint options:
     };
 
     println!("Lint groups provided by rustc:\n");
-    println!("    {}  {}", padded("name"), "sub-lints");
-    println!("    {}  {}", padded("----"), "---------");
-    println!("    {}  {}", padded("warnings"), "all lints that are set to issue warnings");
+    println!("    {}  sub-lints", padded("name"));
+    println!("    {}  ---------", padded("----"));
+    println!("    {}  all lints that are set to issue warnings", padded("warnings"));
 
     let print_lint_groups = |lints: Vec<(&'static str, Vec<LintId>)>| {
         for (name, to) in lints {
@@ -1217,7 +1217,7 @@ pub fn report_ice(info: &panic::PanicInfo<'_>, bug_report_url: &str) {
     }
 
     for note in &xs {
-        handler.note_without_error(&note);
+        handler.note_without_error(note);
     }
 
     // If backtraces are enabled, also print the query stack
@@ -1326,7 +1326,7 @@ mod signal_handler {
                 std::alloc::alloc(std::alloc::Layout::from_size_align(ALT_STACK_SIZE, 1).unwrap())
                     as *mut libc::c_void;
             alt_stack.ss_size = ALT_STACK_SIZE;
-            libc::sigaltstack(&mut alt_stack, std::ptr::null_mut());
+            libc::sigaltstack(&alt_stack, std::ptr::null_mut());
 
             let mut sa: libc::sigaction = std::mem::zeroed();
             sa.sa_sigaction = print_stack_trace as libc::sighandler_t;
diff --git a/compiler/rustc_driver/src/pretty.rs b/compiler/rustc_driver/src/pretty.rs
index a25cc000443..5e7358be7ed 100644
--- a/compiler/rustc_driver/src/pretty.rs
+++ b/compiler/rustc_driver/src/pretty.rs
@@ -296,7 +296,7 @@ struct TypedAnnotation<'tcx> {
 
 impl<'tcx> HirPrinterSupport<'tcx> for TypedAnnotation<'tcx> {
     fn sess(&self) -> &Session {
-        &self.tcx.sess
+        self.tcx.sess
     }
 
     fn hir_map(&self) -> Option<hir_map::Map<'tcx>> {
@@ -347,8 +347,7 @@ impl<'tcx> pprust_hir::PpAnn for TypedAnnotation<'tcx> {
 fn get_source(input: &Input, sess: &Session) -> (String, FileName) {
     let src_name = input.source_name();
     let src = String::clone(
-        &sess
-            .source_map()
+        sess.source_map()
             .get_source_file(&src_name)
             .expect("get_source_file")
             .src
diff --git a/compiler/rustc_interface/src/callbacks.rs b/compiler/rustc_interface/src/callbacks.rs
index 95bd2993456..3c7908fae79 100644
--- a/compiler/rustc_interface/src/callbacks.rs
+++ b/compiler/rustc_interface/src/callbacks.rs
@@ -41,7 +41,7 @@ fn track_span_parent(def_id: rustc_span::def_id::LocalDefId) {
 fn track_diagnostic(diagnostic: &Diagnostic) {
     tls::with_context_opt(|icx| {
         if let Some(icx) = icx {
-            if let Some(ref diagnostics) = icx.diagnostics {
+            if let Some(diagnostics) = icx.diagnostics {
                 let mut diagnostics = diagnostics.lock();
                 diagnostics.extend(Some(diagnostic.clone()));
             }
diff --git a/compiler/rustc_interface/src/interface.rs b/compiler/rustc_interface/src/interface.rs
index 8393826aa12..0861bd290df 100644
--- a/compiler/rustc_interface/src/interface.rs
+++ b/compiler/rustc_interface/src/interface.rs
@@ -65,13 +65,7 @@ impl Compiler {
         sess: &Session,
         attrs: &[ast::Attribute],
     ) -> OutputFilenames {
-        util::build_output_filenames(
-            &self.input,
-            &self.output_dir,
-            &self.output_file,
-            &attrs,
-            &sess,
-        )
+        util::build_output_filenames(&self.input, &self.output_dir, &self.output_file, attrs, sess)
     }
 }
 
diff --git a/compiler/rustc_interface/src/passes.rs b/compiler/rustc_interface/src/passes.rs
index 55a3fcd0266..977c700bd97 100644
--- a/compiler/rustc_interface/src/passes.rs
+++ b/compiler/rustc_interface/src/passes.rs
@@ -169,7 +169,7 @@ pub fn create_resolver(
 ) -> BoxedResolver {
     tracing::trace!("create_resolver");
     BoxedResolver::new(sess, move |sess, resolver_arenas| {
-        Resolver::new(sess, &krate, &crate_name, metadata_loader, &resolver_arenas)
+        Resolver::new(sess, krate, crate_name, metadata_loader, resolver_arenas)
     })
 }
 
@@ -201,7 +201,7 @@ pub fn register_plugins<'a>(
         sess.opts.cg.metadata.clone(),
     );
     sess.stable_crate_id.set(stable_crate_id).expect("not yet initialized");
-    rustc_incremental::prepare_session_directory(sess, &crate_name, stable_crate_id)?;
+    rustc_incremental::prepare_session_directory(sess, crate_name, stable_crate_id)?;
 
     if sess.opts.incremental.is_some() {
         sess.time("incr_comp_garbage_collect_session_directories", || {
@@ -219,7 +219,7 @@ pub fn register_plugins<'a>(
         sess.opts.debugging_opts.no_interleave_lints,
         sess.unstable_options(),
     );
-    register_lints(&sess, &mut lint_store);
+    register_lints(sess, &mut lint_store);
 
     let registrars =
         sess.time("plugin_loading", || plugin::load::load_plugins(sess, metadata_loader, &krate));
@@ -244,7 +244,7 @@ fn pre_expansion_lint(
         rustc_lint::check_ast_crate(
             sess,
             lint_store,
-            &krate,
+            krate,
             crate_attrs,
             true,
             None,
@@ -270,10 +270,10 @@ pub fn configure_and_expand(
 
     krate = sess.time("crate_injection", || {
         let alt_std_name = sess.opts.alt_std_name.as_ref().map(|s| Symbol::intern(s));
-        rustc_builtin_macros::standard_library_imports::inject(krate, resolver, &sess, alt_std_name)
+        rustc_builtin_macros::standard_library_imports::inject(krate, resolver, sess, alt_std_name)
     });
 
-    util::check_attr_crate_type(&sess, &krate.attrs, &mut resolver.lint_buffer());
+    util::check_attr_crate_type(sess, &krate.attrs, &mut resolver.lint_buffer());
 
     // Expand all macros
     krate = sess.time("macro_expand_crate", || {
@@ -310,9 +310,9 @@ pub fn configure_and_expand(
 
         // Create the config for macro expansion
         let features = sess.features_untracked();
-        let recursion_limit = get_recursion_limit(&krate.attrs, &sess);
+        let recursion_limit = get_recursion_limit(&krate.attrs, sess);
         let cfg = rustc_expand::expand::ExpansionConfig {
-            features: Some(&features),
+            features: Some(features),
             recursion_limit,
             trace_mac: sess.opts.debugging_opts.trace_macros,
             should_test: sess.opts.test,
@@ -327,7 +327,7 @@ pub fn configure_and_expand(
             pre_expansion_lint(sess, lint_store, &krate, &crate_attrs, &ident.name.as_str());
             (krate.attrs, krate.items)
         };
-        let mut ecx = ExtCtxt::new(&sess, cfg, resolver, Some(&extern_mod_loaded));
+        let mut ecx = ExtCtxt::new(sess, cfg, resolver, Some(&extern_mod_loaded));
 
         // Expand macros now!
         let krate = sess.time("expand_crate", || ecx.monotonic_expander().expand_crate(krate));
@@ -369,7 +369,7 @@ pub fn configure_and_expand(
     })?;
 
     sess.time("maybe_building_test_harness", || {
-        rustc_builtin_macros::test_harness::inject(&sess, resolver, &mut krate)
+        rustc_builtin_macros::test_harness::inject(sess, resolver, &mut krate)
     });
 
     if let Some(PpMode::Source(PpSourceMode::EveryBodyLoops)) = sess.opts.pretty {
@@ -392,8 +392,8 @@ pub fn configure_and_expand(
     // start passing '--crate-type proc-macro'
     if has_proc_macro_decls && sess.opts.actually_rustdoc && !is_proc_macro_crate {
         let mut msg = sess.diagnostic().struct_warn(
-            &"Trying to document proc macro crate \
-            without passing '--crate-type proc-macro to rustdoc",
+            "Trying to document proc macro crate \
+             without passing '--crate-type proc-macro to rustdoc",
         );
 
         msg.warn("The generated documentation may be incorrect");
@@ -403,7 +403,7 @@ pub fn configure_and_expand(
             let num_crate_types = crate_types.len();
             let is_test_crate = sess.opts.test;
             rustc_builtin_macros::proc_macro_harness::inject(
-                &sess,
+                sess,
                 resolver,
                 krate,
                 is_proc_macro_crate,
@@ -691,7 +691,7 @@ pub fn prepare_outputs(
     );
 
     let output_paths =
-        generated_output_paths(sess, &outputs, compiler.output_file.is_some(), &crate_name);
+        generated_output_paths(sess, &outputs, compiler.output_file.is_some(), crate_name);
 
     // Ensure the source file isn't accidentally overwritten during compilation.
     if let Some(ref input_path) = compiler.input_path {
@@ -832,7 +832,7 @@ pub fn create_global_ctxt<'tcx>(
                 dep_graph,
                 queries.on_disk_cache.as_ref().map(OnDiskCache::as_dyn),
                 queries.as_dyn(),
-                &crate_name,
+                crate_name,
                 outputs,
             )
         })
diff --git a/compiler/rustc_interface/src/queries.rs b/compiler/rustc_interface/src/queries.rs
index a71b59b9d49..f188ad35605 100644
--- a/compiler/rustc_interface/src/queries.rs
+++ b/compiler/rustc_interface/src/queries.rs
@@ -110,7 +110,7 @@ impl<'tcx> Queries<'tcx> {
         &self.compiler.sess
     }
     fn codegen_backend(&self) -> &Lrc<Box<dyn CodegenBackend>> {
-        &self.compiler.codegen_backend()
+        self.compiler.codegen_backend()
     }
 
     fn dep_graph_future(&self) -> Result<&Query<Option<DepGraphFuture>>> {
@@ -181,7 +181,7 @@ impl<'tcx> Queries<'tcx> {
                 &crate_name,
             );
             let krate = resolver.access(|resolver| {
-                passes::configure_and_expand(&sess, &lint_store, krate, &crate_name, resolver)
+                passes::configure_and_expand(sess, &lint_store, krate, &crate_name, resolver)
             })?;
             Ok((Rc::new(krate), Rc::new(RefCell::new(resolver)), lint_store))
         })
@@ -343,7 +343,7 @@ impl Linker {
         let sess = &self.sess;
         let dep_graph = self.dep_graph;
         sess.time("serialize_work_products", || {
-            rustc_incremental::save_work_product_index(&sess, &dep_graph, work_products)
+            rustc_incremental::save_work_product_index(sess, &dep_graph, work_products)
         });
 
         let prof = self.sess.prof.clone();
@@ -386,7 +386,7 @@ impl Compiler {
         F: for<'tcx> FnOnce(&'tcx Queries<'tcx>) -> T,
     {
         let mut _timer = None;
-        let queries = Queries::new(&self);
+        let queries = Queries::new(self);
         let ret = f(&queries);
 
         // NOTE: intentionally does not compute the global context if it hasn't been built yet,
diff --git a/compiler/rustc_interface/src/util.rs b/compiler/rustc_interface/src/util.rs
index a1d1b63c8fa..cffb087af18 100644
--- a/compiler/rustc_interface/src/util.rs
+++ b/compiler/rustc_interface/src/util.rs
@@ -402,7 +402,7 @@ pub fn get_codegen_sysroot(
         .iter()
         .chain(sysroot_candidates.iter())
         .map(|sysroot| {
-            filesearch::make_target_lib_path(&sysroot, &target).with_file_name("codegen-backends")
+            filesearch::make_target_lib_path(sysroot, target).with_file_name("codegen-backends")
         })
         .find(|f| {
             info!("codegen backend candidate: {}", f.display());
@@ -619,7 +619,7 @@ pub fn build_output_filenames(
                 .opts
                 .crate_name
                 .clone()
-                .or_else(|| rustc_attr::find_crate_name(&sess, attrs).map(|n| n.to_string()))
+                .or_else(|| rustc_attr::find_crate_name(sess, attrs).map(|n| n.to_string()))
                 .unwrap_or_else(|| input.filestem().to_owned());
 
             OutputFilenames::new(
diff --git a/compiler/rustc_llvm/src/lib.rs b/compiler/rustc_llvm/src/lib.rs
index 2f199989d3b..6493bd91ca2 100644
--- a/compiler/rustc_llvm/src/lib.rs
+++ b/compiler/rustc_llvm/src/lib.rs
@@ -17,6 +17,10 @@ impl RustString {
     pub fn len(&self) -> usize {
         self.bytes.borrow().len()
     }
+
+    pub fn is_empty(&self) -> bool {
+        self.bytes.borrow().is_empty()
+    }
 }
 
 /// Appending to a Rust string -- used by RawRustStringOstream.
diff --git a/compiler/rustc_privacy/src/lib.rs b/compiler/rustc_privacy/src/lib.rs
index e14f758ddae..7e404749da8 100644
--- a/compiler/rustc_privacy/src/lib.rs
+++ b/compiler/rustc_privacy/src/lib.rs
@@ -470,7 +470,7 @@ impl EmbargoVisitor<'tcx> {
 
         let hir_id = self.tcx.hir().local_def_id_to_hir_id(local_def_id);
         let attrs = self.tcx.hir().attrs(hir_id);
-        if attr::find_transparency(&attrs, md.macro_rules).0 != Transparency::Opaque {
+        if attr::find_transparency(attrs, md.macro_rules).0 != Transparency::Opaque {
             return;
         }
 
@@ -797,7 +797,7 @@ impl Visitor<'tcx> for EmbargoVisitor<'tcx> {
             // Re-exports are handled in `visit_mod`. However, in order to avoid looping over
             // all of the items of a mod in `visit_mod` looking for use statements, we handle
             // making sure that intermediate use statements have their visibilities updated here.
-            hir::ItemKind::Use(ref path, _) => {
+            hir::ItemKind::Use(path, _) => {
                 if item_level.is_some() {
                     self.update_visibility_of_intermediate_use_statements(path.segments.as_ref());
                 }
@@ -1099,11 +1099,11 @@ impl<'tcx> Visitor<'tcx> for NamePrivacyVisitor<'tcx> {
     }
 
     fn visit_expr(&mut self, expr: &'tcx hir::Expr<'tcx>) {
-        if let hir::ExprKind::Struct(ref qpath, fields, ref base) = expr.kind {
+        if let hir::ExprKind::Struct(qpath, fields, ref base) = expr.kind {
             let res = self.typeck_results().qpath_res(qpath, expr.hir_id);
             let adt = self.typeck_results().expr_ty(expr).ty_adt_def().unwrap();
             let variant = adt.variant_of_res(res);
-            if let Some(ref base) = *base {
+            if let Some(base) = *base {
                 // If the expression uses FRU we need to make sure all the unmentioned fields
                 // are checked for privacy (RFC 736). Rather than computing the set of
                 // unmentioned fields, just check them all.
@@ -1312,7 +1312,7 @@ impl<'tcx> Visitor<'tcx> for TypePrivacyVisitor<'tcx> {
             return;
         }
         match expr.kind {
-            hir::ExprKind::Assign(_, ref rhs, _) | hir::ExprKind::Match(ref rhs, ..) => {
+            hir::ExprKind::Assign(_, rhs, _) | hir::ExprKind::Match(rhs, ..) => {
                 // Do not report duplicate errors for `x = y` and `match x { ... }`.
                 if self.check_expr_pat_type(rhs.hir_id, rhs.span) {
                     return;
@@ -1397,7 +1397,7 @@ impl<'tcx> Visitor<'tcx> for TypePrivacyVisitor<'tcx> {
     }
 
     fn visit_local(&mut self, local: &'tcx hir::Local<'tcx>) {
-        if let Some(ref init) = local.init {
+        if let Some(init) = local.init {
             if self.check_expr_pat_type(init.hir_id, init.span) {
                 // Do not report duplicate errors for `let x = y`.
                 return;
@@ -1474,7 +1474,7 @@ impl<'a, 'tcx> ObsoleteVisiblePrivateTypesVisitor<'a, 'tcx> {
             // .. and it corresponds to a private type in the AST (this returns
             // `None` for type parameters).
             match self.tcx.hir().find(self.tcx.hir().local_def_id_to_hir_id(did)) {
-                Some(Node::Item(ref item)) => !item.vis.node.is_pub(),
+                Some(Node::Item(item)) => !item.vis.node.is_pub(),
                 Some(_) | None => false,
             }
         } else {
@@ -1490,7 +1490,7 @@ impl<'a, 'tcx> ObsoleteVisiblePrivateTypesVisitor<'a, 'tcx> {
 
     fn check_generic_bound(&mut self, bound: &hir::GenericBound<'_>) {
         if let hir::GenericBound::Trait(ref trait_ref, _) = *bound {
-            if self.path_is_private_type(&trait_ref.trait_ref.path) {
+            if self.path_is_private_type(trait_ref.trait_ref.path) {
                 self.old_error_set.insert(trait_ref.trait_ref.hir_ref_id);
             }
         }
@@ -1517,7 +1517,7 @@ impl<'a, 'b, 'tcx, 'v> Visitor<'v> for ObsoleteCheckTypeForPrivatenessVisitor<'a
     }
 
     fn visit_ty(&mut self, ty: &hir::Ty<'_>) {
-        if let hir::TyKind::Path(hir::QPath::Resolved(_, ref path)) = ty.kind {
+        if let hir::TyKind::Path(hir::QPath::Resolved(_, path)) = ty.kind {
             if self.inner.path_is_private_type(path) {
                 self.contains_private = true;
                 // Found what we're looking for, so let's stop working.
@@ -1556,7 +1556,7 @@ impl<'a, 'tcx> Visitor<'tcx> for ObsoleteVisiblePrivateTypesVisitor<'a, 'tcx> {
             // namespace (the contents have their own privacies).
             hir::ItemKind::ForeignMod { .. } => {}
 
-            hir::ItemKind::Trait(.., ref bounds, _) => {
+            hir::ItemKind::Trait(.., bounds, _) => {
                 if !self.trait_is_public(item.def_id) {
                     return;
                 }
@@ -1586,7 +1586,7 @@ impl<'a, 'tcx> Visitor<'tcx> for ObsoleteVisiblePrivateTypesVisitor<'a, 'tcx> {
                         at_outer_type: true,
                         outer_type_is_public_path: false,
                     };
-                    visitor.visit_ty(&impl_.self_ty);
+                    visitor.visit_ty(impl_.self_ty);
                     self_contains_private = visitor.contains_private;
                     self_is_public_path = visitor.outer_type_is_public_path;
                 }
@@ -1664,12 +1664,12 @@ impl<'a, 'tcx> Visitor<'tcx> for ObsoleteVisiblePrivateTypesVisitor<'a, 'tcx> {
                             //
                             // Those in 2. are warned via walk_generics and this
                             // call here.
-                            intravisit::walk_path(self, &tr.path);
+                            intravisit::walk_path(self, tr.path);
 
                             // Those in 3. are warned with this call.
                             for impl_item_ref in impl_.items {
                                 let impl_item = self.tcx.hir().impl_item(impl_item_ref.id);
-                                if let hir::ImplItemKind::TyAlias(ref ty) = impl_item.kind {
+                                if let hir::ImplItemKind::TyAlias(ty) = impl_item.kind {
                                     self.visit_ty(ty);
                                 }
                             }
@@ -1739,7 +1739,7 @@ impl<'a, 'tcx> Visitor<'tcx> for ObsoleteVisiblePrivateTypesVisitor<'a, 'tcx> {
                 }
                 hir::WherePredicate::RegionPredicate(_) => {}
                 hir::WherePredicate::EqPredicate(eq_pred) => {
-                    self.visit_ty(&eq_pred.rhs_ty);
+                    self.visit_ty(eq_pred.rhs_ty);
                 }
             }
         }
@@ -1752,7 +1752,7 @@ impl<'a, 'tcx> Visitor<'tcx> for ObsoleteVisiblePrivateTypesVisitor<'a, 'tcx> {
     }
 
     fn visit_ty(&mut self, t: &'tcx hir::Ty<'tcx>) {
-        if let hir::TyKind::Path(hir::QPath::Resolved(_, ref path)) = t.kind {
+        if let hir::TyKind::Path(hir::QPath::Resolved(_, path)) = t.kind {
             if self.path_is_private_type(path) {
                 self.old_error_set.insert(t.hir_id);
             }
@@ -2193,7 +2193,7 @@ fn check_private_in_public(tcx: TyCtxt<'_>, (): ()) {
 
     let mut visitor = ObsoleteVisiblePrivateTypesVisitor {
         tcx,
-        access_levels: &access_levels,
+        access_levels,
         in_variant: false,
         old_error_set: Default::default(),
     };
diff --git a/compiler/rustc_typeck/src/astconv/generics.rs b/compiler/rustc_typeck/src/astconv/generics.rs
index 456d3fe7b2f..5befe44802f 100644
--- a/compiler/rustc_typeck/src/astconv/generics.rs
+++ b/compiler/rustc_typeck/src/astconv/generics.rs
@@ -132,7 +132,7 @@ impl<'o, 'tcx> dyn AstConv<'tcx> + 'o {
         }
 
         let kind_ord = param.kind.to_ord(tcx);
-        let arg_ord = arg.to_ord(&tcx.features());
+        let arg_ord = arg.to_ord(tcx.features());
 
         // This note is only true when generic parameters are strictly ordered by their kind.
         if possible_ordering_error && kind_ord.cmp(&arg_ord) != core::cmp::Ordering::Equal {
@@ -423,7 +423,7 @@ impl<'o, 'tcx> dyn AstConv<'tcx> + 'o {
         is_method_call: IsMethodCall,
     ) -> GenericArgCountResult {
         let empty_args = hir::GenericArgs::none();
-        let suppress_mismatch = Self::check_impl_trait(tcx, seg, &generics);
+        let suppress_mismatch = Self::check_impl_trait(tcx, seg, generics);
 
         let gen_args = seg.args.unwrap_or(&empty_args);
         let gen_pos = if is_method_call == IsMethodCall::Yes {
diff --git a/compiler/rustc_typeck/src/astconv/mod.rs b/compiler/rustc_typeck/src/astconv/mod.rs
index 33df541eb2b..e492fd44185 100644
--- a/compiler/rustc_typeck/src/astconv/mod.rs
+++ b/compiler/rustc_typeck/src/astconv/mod.rs
@@ -352,8 +352,8 @@ impl<'o, 'tcx> dyn AstConv<'tcx> + 'o {
             span,
             def_id,
             seg,
-            &generics,
-            &generic_args,
+            generics,
+            generic_args,
             GenericArgPosition::Type,
             self_ty.is_some(),
             infer_args,
@@ -363,7 +363,7 @@ impl<'o, 'tcx> dyn AstConv<'tcx> + 'o {
         // Traits always have `Self` as a generic parameter, which means they will not return early
         // here and so associated type bindings will be handled regardless of whether there are any
         // non-`Self` generic parameters.
-        if generics.params.len() == 0 {
+        if generics.params.is_empty() {
             return (tcx.intern_substs(&[]), arg_count);
         }
 
@@ -417,7 +417,7 @@ impl<'o, 'tcx> dyn AstConv<'tcx> + 'o {
                 let tcx = self.astconv.tcx();
                 match (&param.kind, arg) {
                     (GenericParamDefKind::Lifetime, GenericArg::Lifetime(lt)) => {
-                        self.astconv.ast_region_to_region(&lt, Some(param)).into()
+                        self.astconv.ast_region_to_region(lt, Some(param)).into()
                     }
                     (&GenericParamDefKind::Type { has_default, .. }, GenericArg::Type(ty)) => {
                         if has_default {
@@ -441,7 +441,7 @@ impl<'o, 'tcx> dyn AstConv<'tcx> + 'o {
                             self.inferred_params.push(ty.span);
                             tcx.ty_error().into()
                         } else {
-                            self.astconv.ast_ty_to_ty(&ty).into()
+                            self.astconv.ast_ty_to_ty(ty).into()
                         }
                     }
                     (GenericParamDefKind::Const { .. }, GenericArg::Const(ct)) => {
@@ -622,10 +622,10 @@ impl<'o, 'tcx> dyn AstConv<'tcx> + 'o {
             .iter()
             .map(|binding| {
                 let kind = match binding.kind {
-                    hir::TypeBindingKind::Equality { ref ty } => {
+                    hir::TypeBindingKind::Equality { ty } => {
                         ConvertedBindingKind::Equality(self.ast_ty_to_ty(ty))
                     }
-                    hir::TypeBindingKind::Constraint { ref bounds } => {
+                    hir::TypeBindingKind::Constraint { bounds } => {
                         ConvertedBindingKind::Constraint(bounds)
                     }
                 };
@@ -908,18 +908,15 @@ impl<'o, 'tcx> dyn AstConv<'tcx> + 'o {
         if let Some((self_ty, where_clause)) = self_ty_where_predicates {
             let self_ty_def_id = tcx.hir().local_def_id(self_ty).to_def_id();
             for clause in where_clause {
-                match clause {
-                    hir::WherePredicate::BoundPredicate(pred) => {
-                        match pred.bounded_ty.kind {
-                            hir::TyKind::Path(hir::QPath::Resolved(_, path)) => match path.res {
-                                Res::Def(DefKind::TyParam, def_id) if def_id == self_ty_def_id => {}
-                                _ => continue,
-                            },
+                if let hir::WherePredicate::BoundPredicate(pred) = clause {
+                    match pred.bounded_ty.kind {
+                        hir::TyKind::Path(hir::QPath::Resolved(_, path)) => match path.res {
+                            Res::Def(DefKind::TyParam, def_id) if def_id == self_ty_def_id => {}
                             _ => continue,
-                        }
-                        search_bounds(pred.bounds);
+                        },
+                        _ => continue,
                     }
-                    _ => {}
+                    search_bounds(pred.bounds);
                 }
             }
         }
@@ -1030,7 +1027,7 @@ impl<'o, 'tcx> dyn AstConv<'tcx> + 'o {
         param_ty: Ty<'tcx>,
         ast_bounds: &[hir::GenericBound<'_>],
     ) -> Bounds<'tcx> {
-        self.compute_bounds_inner(param_ty, &ast_bounds)
+        self.compute_bounds_inner(param_ty, ast_bounds)
     }
 
     /// Convert the bounds in `ast_bounds` that refer to traits which define an associated type
@@ -1231,7 +1228,7 @@ impl<'o, 'tcx> dyn AstConv<'tcx> + 'o {
         }
 
         match binding.kind {
-            ConvertedBindingKind::Equality(ref ty) => {
+            ConvertedBindingKind::Equality(ty) => {
                 // "Desugar" a constraint like `T: Iterator<Item = u32>` this to
                 // the "projection predicate" for:
                 //
@@ -2207,7 +2204,7 @@ impl<'o, 'tcx> dyn AstConv<'tcx> + 'o {
                 assert_eq!(opt_self_ty, None);
 
                 let path_segs =
-                    self.def_ids_for_value_path_segments(&path.segments, None, kind, def_id);
+                    self.def_ids_for_value_path_segments(path.segments, None, kind, def_id);
                 let generic_segs: FxHashSet<_> =
                     path_segs.iter().map(|PathSeg(_, index)| index).collect();
                 self.prohibit_generics(path.segments.iter().enumerate().filter_map(
@@ -2304,34 +2301,32 @@ impl<'o, 'tcx> dyn AstConv<'tcx> + 'o {
         let tcx = self.tcx();
 
         let result_ty = match ast_ty.kind {
-            hir::TyKind::Slice(ref ty) => tcx.mk_slice(self.ast_ty_to_ty(&ty)),
+            hir::TyKind::Slice(ref ty) => tcx.mk_slice(self.ast_ty_to_ty(ty)),
             hir::TyKind::Ptr(ref mt) => {
-                tcx.mk_ptr(ty::TypeAndMut { ty: self.ast_ty_to_ty(&mt.ty), mutbl: mt.mutbl })
+                tcx.mk_ptr(ty::TypeAndMut { ty: self.ast_ty_to_ty(mt.ty), mutbl: mt.mutbl })
             }
             hir::TyKind::Rptr(ref region, ref mt) => {
                 let r = self.ast_region_to_region(region, None);
                 debug!(?r);
-                let t = self.ast_ty_to_ty_inner(&mt.ty, true);
+                let t = self.ast_ty_to_ty_inner(mt.ty, true);
                 tcx.mk_ref(r, ty::TypeAndMut { ty: t, mutbl: mt.mutbl })
             }
             hir::TyKind::Never => tcx.types.never,
-            hir::TyKind::Tup(ref fields) => {
-                tcx.mk_tup(fields.iter().map(|t| self.ast_ty_to_ty(&t)))
-            }
-            hir::TyKind::BareFn(ref bf) => {
-                require_c_abi_if_c_variadic(tcx, &bf.decl, bf.abi, ast_ty.span);
+            hir::TyKind::Tup(fields) => tcx.mk_tup(fields.iter().map(|t| self.ast_ty_to_ty(t))),
+            hir::TyKind::BareFn(bf) => {
+                require_c_abi_if_c_variadic(tcx, bf.decl, bf.abi, ast_ty.span);
 
                 tcx.mk_fn_ptr(self.ty_of_fn(
                     ast_ty.hir_id,
                     bf.unsafety,
                     bf.abi,
-                    &bf.decl,
+                    bf.decl,
                     &hir::Generics::empty(),
                     None,
                     Some(ast_ty),
                 ))
             }
-            hir::TyKind::TraitObject(ref bounds, ref lifetime, _) => {
+            hir::TyKind::TraitObject(bounds, ref lifetime, _) => {
                 self.conv_object_ty_poly_trait_ref(ast_ty.span, bounds, lifetime, borrowed)
             }
             hir::TyKind::Path(hir::QPath::Resolved(ref maybe_qself, ref path)) => {
@@ -2339,7 +2334,7 @@ impl<'o, 'tcx> dyn AstConv<'tcx> + 'o {
                 let opt_self_ty = maybe_qself.as_ref().map(|qself| self.ast_ty_to_ty(qself));
                 self.res_to_ty(opt_self_ty, path, false)
             }
-            hir::TyKind::OpaqueDef(item_id, ref lifetimes) => {
+            hir::TyKind::OpaqueDef(item_id, lifetimes) => {
                 let opaque_ty = tcx.hir().item(item_id);
                 let def_id = item_id.def_id.to_def_id();
 
@@ -2354,7 +2349,7 @@ impl<'o, 'tcx> dyn AstConv<'tcx> + 'o {
                 debug!(?qself, ?segment);
                 let ty = self.ast_ty_to_ty(qself);
 
-                let res = if let hir::TyKind::Path(hir::QPath::Resolved(_, ref path)) = qself.kind {
+                let res = if let hir::TyKind::Path(hir::QPath::Resolved(_, path)) = qself.kind {
                     path.res
                 } else {
                     Res::Err
@@ -2379,7 +2374,7 @@ impl<'o, 'tcx> dyn AstConv<'tcx> + 'o {
             hir::TyKind::Array(ref ty, ref length) => {
                 let length_def_id = tcx.hir().local_def_id(length.hir_id);
                 let length = ty::Const::from_anon_const(tcx, length_def_id);
-                let array_ty = tcx.mk_ty(ty::Array(self.ast_ty_to_ty(&ty), length));
+                let array_ty = tcx.mk_ty(ty::Array(self.ast_ty_to_ty(ty), length));
                 self.normalize_ty(ast_ty.span, array_ty)
             }
             hir::TyKind::Typeof(ref e) => {
@@ -2485,7 +2480,7 @@ impl<'o, 'tcx> dyn AstConv<'tcx> + 'o {
 
         let input_tys = decl.inputs.iter().map(|a| self.ty_of_arg(a, None));
         let output_ty = match decl.output {
-            hir::FnRetTy::Return(ref output) => {
+            hir::FnRetTy::Return(output) => {
                 visitor.visit_ty(output);
                 self.ast_ty_to_ty(output)
             }
diff --git a/compiler/rustc_typeck/src/check/method/confirm.rs b/compiler/rustc_typeck/src/check/method/confirm.rs
index 88be49e96e7..dc54f63f49c 100644
--- a/compiler/rustc_typeck/src/check/method/confirm.rs
+++ b/compiler/rustc_typeck/src/check/method/confirm.rs
@@ -28,7 +28,7 @@ struct ConfirmContext<'a, 'tcx> {
 impl<'a, 'tcx> Deref for ConfirmContext<'a, 'tcx> {
     type Target = FnCtxt<'a, 'tcx>;
     fn deref(&self) -> &Self::Target {
-        &self.fcx
+        self.fcx
     }
 }
 
@@ -290,7 +290,7 @@ impl<'a, 'tcx> ConfirmContext<'a, 'tcx> {
             .autoderef(self.span, self_ty)
             .include_raw_pointers()
             .find_map(|(ty, _)| match ty.kind() {
-                ty::Dynamic(ref data, ..) => Some(closure(
+                ty::Dynamic(data, ..) => Some(closure(
                     self,
                     ty,
                     data.principal().unwrap_or_else(|| {
@@ -323,7 +323,7 @@ impl<'a, 'tcx> ConfirmContext<'a, 'tcx> {
             self.tcx,
             self.span,
             pick.item.def_id,
-            &generics,
+            generics,
             seg,
             IsMethodCall::Yes,
         );
@@ -343,7 +343,7 @@ impl<'a, 'tcx> ConfirmContext<'a, 'tcx> {
                 def_id: DefId,
             ) -> (Option<&'a hir::GenericArgs<'a>>, bool) {
                 if def_id == self.pick.item.def_id {
-                    if let Some(ref data) = self.seg.args {
+                    if let Some(data) = self.seg.args {
                         return (Some(data), false);
                     }
                 }
diff --git a/compiler/rustc_typeck/src/check/method/mod.rs b/compiler/rustc_typeck/src/check/method/mod.rs
index 113d495f0ce..65b3ceb8698 100644
--- a/compiler/rustc_typeck/src/check/method/mod.rs
+++ b/compiler/rustc_typeck/src/check/method/mod.rs
@@ -160,7 +160,7 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
             .unwrap_or(0);
 
         // Account for `foo.bar<T>`;
-        let sugg_span = span.unwrap_or_else(|| call_expr.span).shrink_to_hi();
+        let sugg_span = span.unwrap_or(call_expr.span).shrink_to_hi();
         let (suggestion, applicability) = (
             format!("({})", (0..params).map(|_| "_").collect::<Vec<_>>().join(", ")),
             if params > 0 { Applicability::HasPlaceholders } else { Applicability::MaybeIncorrect },
@@ -320,7 +320,7 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
                 GenericParamDefKind::Type { .. } => {
                     if param.index == 0 {
                         return self_ty.into();
-                    } else if let Some(ref input_types) = opt_input_types {
+                    } else if let Some(input_types) = opt_input_types {
                         return input_types[param.index as usize - 1].into();
                     }
                 }
diff --git a/compiler/rustc_typeck/src/check/method/probe.rs b/compiler/rustc_typeck/src/check/method/probe.rs
index 5aa579f33a9..9d6db32be63 100644
--- a/compiler/rustc_typeck/src/check/method/probe.rs
+++ b/compiler/rustc_typeck/src/check/method/probe.rs
@@ -88,7 +88,7 @@ struct ProbeContext<'a, 'tcx> {
 impl<'a, 'tcx> Deref for ProbeContext<'a, 'tcx> {
     type Target = FnCtxt<'a, 'tcx>;
     fn deref(&self) -> &Self::Target {
-        &self.fcx
+        self.fcx
     }
 }
 
@@ -614,7 +614,7 @@ impl<'a, 'tcx> ProbeContext<'a, 'tcx> {
         let lang_items = self.tcx.lang_items();
 
         match *self_ty.value.value.kind() {
-            ty::Dynamic(ref data, ..) if let Some(p) = data.principal() => {
+            ty::Dynamic(data, ..) if let Some(p) = data.principal() => {
                 // Subtle: we can't use `instantiate_query_response` here: using it will
                 // commit to all of the type equalities assumed by inference going through
                 // autoderef (see the `method-probe-no-guessing` test).
@@ -634,7 +634,7 @@ impl<'a, 'tcx> ProbeContext<'a, 'tcx> {
                 // type variables in any form, so just do that!
                 let (QueryResponse { value: generalized_self_ty, .. }, _ignored_var_values) =
                     self.fcx
-                        .instantiate_canonical_with_fresh_inference_vars(self.span, &self_ty);
+                        .instantiate_canonical_with_fresh_inference_vars(self.span, self_ty);
 
                 self.assemble_inherent_candidates_from_object(generalized_self_ty);
                 self.assemble_inherent_impl_candidates_for_type(p.def_id());
@@ -1428,7 +1428,7 @@ impl<'a, 'tcx> ProbeContext<'a, 'tcx> {
             // match as well (or at least may match, sometimes we
             // don't have enough information to fully evaluate).
             match probe.kind {
-                InherentImplCandidate(ref substs, ref ref_obligations) => {
+                InherentImplCandidate(substs, ref ref_obligations) => {
                     // Check whether the impl imposes obligations we have to worry about.
                     let impl_def_id = probe.item.container.id();
                     let impl_bounds = self.tcx.predicates_of(impl_def_id);
diff --git a/compiler/rustc_typeck/src/check/method/suggest.rs b/compiler/rustc_typeck/src/check/method/suggest.rs
index 9c7853dd78d..3e0c303cadf 100644
--- a/compiler/rustc_typeck/src/check/method/suggest.rs
+++ b/compiler/rustc_typeck/src/check/method/suggest.rs
@@ -328,48 +328,44 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
                                     Applicability::MaybeIncorrect,
                                 );
                             }
-                            ExprKind::Path(ref qpath) => {
+                            ExprKind::Path(QPath::Resolved(_, path)) => {
                                 // local binding
-                                if let QPath::Resolved(_, path) = qpath {
-                                    if let hir::def::Res::Local(hir_id) = path.res {
-                                        let span = tcx.hir().span(hir_id);
-                                        let snippet = tcx.sess.source_map().span_to_snippet(span);
-                                        let filename = tcx.sess.source_map().span_to_filename(span);
-
-                                        let parent_node = self
-                                            .tcx
-                                            .hir()
-                                            .get(self.tcx.hir().get_parent_node(hir_id));
-                                        let msg = format!(
-                                            "you must specify a type for this binding, like `{}`",
-                                            concrete_type,
-                                        );
-
-                                        match (filename, parent_node, snippet) {
-                                            (
-                                                FileName::Real(_),
-                                                Node::Local(hir::Local {
-                                                    source: hir::LocalSource::Normal,
-                                                    ty,
-                                                    ..
-                                                }),
-                                                Ok(ref snippet),
-                                            ) => {
-                                                err.span_suggestion(
-                                                    // account for `let x: _ = 42;`
-                                                    //                  ^^^^
-                                                    span.to(ty
-                                                        .as_ref()
-                                                        .map(|ty| ty.span)
-                                                        .unwrap_or(span)),
-                                                    &msg,
-                                                    format!("{}: {}", snippet, concrete_type),
-                                                    Applicability::MaybeIncorrect,
-                                                );
-                                            }
-                                            _ => {
-                                                err.span_label(span, msg);
-                                            }
+                                if let hir::def::Res::Local(hir_id) = path.res {
+                                    let span = tcx.hir().span(hir_id);
+                                    let snippet = tcx.sess.source_map().span_to_snippet(span);
+                                    let filename = tcx.sess.source_map().span_to_filename(span);
+
+                                    let parent_node =
+                                        self.tcx.hir().get(self.tcx.hir().get_parent_node(hir_id));
+                                    let msg = format!(
+                                        "you must specify a type for this binding, like `{}`",
+                                        concrete_type,
+                                    );
+
+                                    match (filename, parent_node, snippet) {
+                                        (
+                                            FileName::Real(_),
+                                            Node::Local(hir::Local {
+                                                source: hir::LocalSource::Normal,
+                                                ty,
+                                                ..
+                                            }),
+                                            Ok(ref snippet),
+                                        ) => {
+                                            err.span_suggestion(
+                                                // account for `let x: _ = 42;`
+                                                //                  ^^^^
+                                                span.to(ty
+                                                    .as_ref()
+                                                    .map(|ty| ty.span)
+                                                    .unwrap_or(span)),
+                                                &msg,
+                                                format!("{}: {}", snippet, concrete_type),
+                                                Applicability::MaybeIncorrect,
+                                            );
+                                        }
+                                        _ => {
+                                            err.span_label(span, msg);
                                         }
                                     }
                                 }
@@ -383,11 +379,11 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
 
                         // Don't show generic arguments when the method can't be found in any implementation (#81576).
                         let mut ty_str_reported = ty_str.clone();
-                        if let ty::Adt(_, ref generics) = actual.kind() {
+                        if let ty::Adt(_, generics) = actual.kind() {
                             if generics.len() > 0 {
                                 let mut autoderef = self.autoderef(span, actual);
                                 let candidate_found = autoderef.any(|(ty, _)| {
-                                    if let ty::Adt(ref adt_deref, _) = ty.kind() {
+                                    if let ty::Adt(adt_deref, _) = ty.kind() {
                                         self.tcx
                                             .inherent_impls(adt_deref.did)
                                             .iter()
@@ -482,7 +478,7 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
                 let mut label_span_not_found = || {
                     if unsatisfied_predicates.is_empty() {
                         err.span_label(span, format!("{item_kind} not found in `{ty_str}`"));
-                        if let ty::Adt(ref adt, _) = rcvr_ty.kind() {
+                        if let ty::Adt(adt, _) = rcvr_ty.kind() {
                             let mut inherent_impls_candidate = self
                                 .tcx
                                 .inherent_impls(adt.did)
@@ -511,7 +507,7 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
                                     }
                                 })
                                 .collect::<Vec<_>>();
-                            if inherent_impls_candidate.len() > 0 {
+                            if !inherent_impls_candidate.is_empty() {
                                 inherent_impls_candidate.sort();
                                 inherent_impls_candidate.dedup();
 
@@ -565,7 +561,7 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
                         let is_accessible = field.vis.is_accessible_from(scope, self.tcx);
 
                         if is_accessible {
-                            if self.is_fn_ty(&field_ty, span) {
+                            if self.is_fn_ty(field_ty, span) {
                                 let expr_span = expr.span.to(item_name.span);
                                 err.multipart_suggestion(
                                     &format!(
@@ -605,7 +601,7 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
                     label_span_not_found();
                 }
 
-                if self.is_fn_ty(&rcvr_ty, span) {
+                if self.is_fn_ty(rcvr_ty, span) {
                     fn report_function<T: std::fmt::Display>(
                         err: &mut DiagnosticBuilder<'_>,
                         name: T,
@@ -618,7 +614,7 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
                     if let SelfSource::MethodCall(expr) = source {
                         if let Ok(expr_string) = tcx.sess.source_map().span_to_snippet(expr.span) {
                             report_function(&mut err, expr_string);
-                        } else if let ExprKind::Path(QPath::Resolved(_, ref path)) = expr.kind {
+                        } else if let ExprKind::Path(QPath::Resolved(_, path)) = expr.kind {
                             if let Some(segment) = path.segments.last() {
                                 report_function(&mut err, segment.ident);
                             }
@@ -808,7 +804,7 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
                         );
                     }
 
-                    bound_list.sort_by(|(_, a), (_, b)| a.cmp(&b)); // Sort alphabetically.
+                    bound_list.sort_by(|(_, a), (_, b)| a.cmp(b)); // Sort alphabetically.
                     bound_list.dedup_by(|(_, a), (_, b)| a == b); // #35677
                     bound_list.sort_by_key(|(pos, _)| *pos); // Keep the original predicate order.
                     bound_spans.sort();
@@ -1007,12 +1003,7 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
                 if adt_def.did.is_local() {
                     let diagnostic_items = self.tcx.diagnostic_items(trait_ref.def_id.krate);
                     return derivables.iter().find_map(|trait_derivable| {
-                        let item_def_id =
-                            if let Some(item_def_id) = diagnostic_items.get(trait_derivable) {
-                                item_def_id
-                            } else {
-                                return None;
-                            };
+                        let item_def_id = diagnostic_items.get(trait_derivable)?;
                         if item_def_id == &trait_pred.trait_ref.def_id
                             && !(adt_def.is_enum() && *trait_derivable == sym::Default)
                         {
@@ -1371,9 +1362,7 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
                 )
             };
             // Obtain the span for `param` and use it for a structured suggestion.
-            if let (Some(ref param), Some(ref table)) =
-                (param_type, self.in_progress_typeck_results)
-            {
+            if let (Some(param), Some(table)) = (param_type, self.in_progress_typeck_results) {
                 let table_owner = table.borrow().hir_owner;
                 let generics = self.tcx.generics_of(table_owner.to_def_id());
                 let type_param = generics.type_param(param, self.tcx);
@@ -1384,7 +1373,7 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
                     // We do this to avoid suggesting code that ends up as `T: FooBar`,
                     // instead we suggest `T: Foo + Bar` in that case.
                     match hir.get(id) {
-                        Node::GenericParam(ref param) => {
+                        Node::GenericParam(param) => {
                             let mut impl_trait = false;
                             let has_bounds =
                                 if let hir::GenericParamKind::Type { synthetic: Some(_), .. } =
@@ -1558,7 +1547,7 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
             match ty.kind() {
                 ty::Adt(def, _) => def.did.is_local(),
                 ty::Foreign(did) => did.is_local(),
-                ty::Dynamic(ref tr, ..) => tr.principal().map_or(false, |d| d.def_id().is_local()),
+                ty::Dynamic(tr, ..) => tr.principal().map_or(false, |d| d.def_id().is_local()),
                 ty::Param(_) => true,
 
                 // Everything else (primitive types, etc.) is effectively
diff --git a/compiler/rustc_typeck/src/check/mod.rs b/compiler/rustc_typeck/src/check/mod.rs
index a10490a9a15..b012aab247c 100644
--- a/compiler/rustc_typeck/src/check/mod.rs
+++ b/compiler/rustc_typeck/src/check/mod.rs
@@ -271,22 +271,22 @@ fn primary_body_of(
 ) -> Option<(hir::BodyId, Option<&hir::Ty<'_>>, Option<&hir::FnSig<'_>>)> {
     match tcx.hir().get(id) {
         Node::Item(item) => match item.kind {
-            hir::ItemKind::Const(ref ty, body) | hir::ItemKind::Static(ref ty, _, body) => {
+            hir::ItemKind::Const(ty, body) | hir::ItemKind::Static(ty, _, body) => {
                 Some((body, Some(ty), None))
             }
-            hir::ItemKind::Fn(ref sig, .., body) => Some((body, None, Some(&sig))),
+            hir::ItemKind::Fn(ref sig, .., body) => Some((body, None, Some(sig))),
             _ => None,
         },
         Node::TraitItem(item) => match item.kind {
-            hir::TraitItemKind::Const(ref ty, Some(body)) => Some((body, Some(ty), None)),
+            hir::TraitItemKind::Const(ty, Some(body)) => Some((body, Some(ty), None)),
             hir::TraitItemKind::Fn(ref sig, hir::TraitFn::Provided(body)) => {
-                Some((body, None, Some(&sig)))
+                Some((body, None, Some(sig)))
             }
             _ => None,
         },
         Node::ImplItem(item) => match item.kind {
-            hir::ImplItemKind::Const(ref ty, body) => Some((body, Some(ty), None)),
-            hir::ImplItemKind::Fn(ref sig, body) => Some((body, None, Some(&sig))),
+            hir::ImplItemKind::Const(ty, body) => Some((body, Some(ty), None)),
+            hir::ImplItemKind::Fn(ref sig, body) => Some((body, None, Some(sig))),
             _ => None,
         },
         Node::AnonConst(constant) => Some((constant.body, None, None)),
@@ -555,16 +555,13 @@ fn maybe_check_static_with_link_section(tcx: TyCtxt<'_>, id: LocalDefId, span: S
     // `#[link_section]` may contain arbitrary, or even undefined bytes, but it is
     // the consumer's responsibility to ensure all bytes that have been read
     // have defined values.
-    match tcx.eval_static_initializer(id.to_def_id()) {
-        Ok(alloc) => {
-            if alloc.relocations().len() != 0 {
-                let msg = "statics with a custom `#[link_section]` must be a \
+    if let Ok(alloc) = tcx.eval_static_initializer(id.to_def_id()) {
+        if alloc.relocations().len() != 0 {
+            let msg = "statics with a custom `#[link_section]` must be a \
                            simple list of bytes on the wasm target with no \
                            extra levels of indirection such as references";
-                tcx.sess.span_err(span, msg);
-            }
+            tcx.sess.span_err(span, msg);
         }
-        Err(_) => {}
     }
 }
 
@@ -631,7 +628,7 @@ fn missing_items_err(
     let padding: String = " ".repeat(indentation);
 
     for trait_item in missing_items {
-        let snippet = suggestion_signature(&trait_item, tcx);
+        let snippet = suggestion_signature(trait_item, tcx);
         let code = format!("{}{}\n{}", padding, snippet, padding);
         let msg = format!("implement the missing item: `{}`", snippet);
         let appl = Applicability::HasPlaceholders;
diff --git a/compiler/rustc_typeck/src/check/op.rs b/compiler/rustc_typeck/src/check/op.rs
index a574a63d63b..d684a18d5cb 100644
--- a/compiler/rustc_typeck/src/check/op.rs
+++ b/compiler/rustc_typeck/src/check/op.rs
@@ -444,7 +444,7 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
                             // Check if the method would be found if the type param wasn't
                             // involved. If so, it means that adding a trait bound to the param is
                             // enough. Otherwise we do not give the suggestion.
-                            let mut eraser = TypeParamEraser(&self, expr.span);
+                            let mut eraser = TypeParamEraser(self, expr.span);
                             let needs_bound = self
                                 .lookup_op_method(
                                     eraser.fold_ty(lhs_ty),
@@ -475,7 +475,7 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
                             bug!("type param visitor stored a non type param: {:?}", ty.kind());
                         }
                     } else if !suggested_deref && !involves_fn {
-                        suggest_impl_missing(&mut err, lhs_ty, &missing_trait);
+                        suggest_impl_missing(&mut err, lhs_ty, missing_trait);
                     }
                 }
                 err.emit();
@@ -718,14 +718,14 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
                                 }
                             }
                             Str | Never | Char | Tuple(_) | Array(_, _) => {}
-                            Ref(_, ref lty, _) if *lty.kind() == Str => {}
+                            Ref(_, lty, _) if *lty.kind() == Str => {}
                             _ => {
                                 let missing_trait = match op {
                                     hir::UnOp::Neg => "std::ops::Neg",
                                     hir::UnOp::Not => "std::ops::Not",
                                     hir::UnOp::Deref => "std::ops::UnDerf",
                                 };
-                                suggest_impl_missing(&mut err, operand_ty, &missing_trait);
+                                suggest_impl_missing(&mut err, operand_ty, missing_trait);
                             }
                         }
                     }
diff --git a/compiler/rustc_typeck/src/check/pat.rs b/compiler/rustc_typeck/src/check/pat.rs
index 829268e3cb5..0650291bacb 100644
--- a/compiler/rustc_typeck/src/check/pat.rs
+++ b/compiler/rustc_typeck/src/check/pat.rs
@@ -341,7 +341,7 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
         expected: Ty<'tcx>,
         mut def_bm: BindingMode,
     ) -> (Ty<'tcx>, BindingMode) {
-        let mut expected = self.resolve_vars_with_obligations(&expected);
+        let mut expected = self.resolve_vars_with_obligations(expected);
 
         // Peel off as many `&` or `&mut` from the scrutinee type as possible. For example,
         // for `match &&&mut Some(5)` the loop runs three times, aborting when it reaches
@@ -587,7 +587,7 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
         }
 
         if let Some(p) = sub {
-            self.check_pat(&p, expected, def_bm, TopInfo { parent_pat: Some(&pat), ..ti });
+            self.check_pat(p, expected, def_bm, TopInfo { parent_pat: Some(pat), ..ti });
         }
 
         local_ty
@@ -697,8 +697,8 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
         } else {
             let err = self.tcx.ty_error();
             for field in fields {
-                let ti = TopInfo { parent_pat: Some(&pat), ..ti };
-                self.check_pat(&field.pat, err, def_bm, ti);
+                let ti = TopInfo { parent_pat: Some(pat), ..ti };
+                self.check_pat(field.pat, err, def_bm, ti);
             }
             return err;
         };
@@ -707,7 +707,7 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
         self.demand_eqtype_pat(pat.span, expected, pat_ty, ti);
 
         // Type-check subpatterns.
-        if self.check_struct_pat_fields(pat_ty, &pat, variant, fields, etc, def_bm, ti) {
+        if self.check_struct_pat_fields(pat_ty, pat, variant, fields, etc, def_bm, ti) {
             pat_ty
         } else {
             self.tcx.ty_error()
@@ -876,7 +876,7 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
         let on_error = || {
             let parent_pat = Some(pat);
             for pat in subpats {
-                self.check_pat(&pat, tcx.ty_error(), def_bm, TopInfo { parent_pat, ..ti });
+                self.check_pat(pat, tcx.ty_error(), def_bm, TopInfo { parent_pat, ..ti });
             }
         };
         let report_unexpected_res = |res: Res| {
@@ -961,7 +961,7 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
             };
             for (i, subpat) in subpats.iter().enumerate_and_adjust(variant.fields.len(), ddpos) {
                 let field_ty = self.field_ty(subpat.span, &variant.fields[i], substs);
-                self.check_pat(&subpat, field_ty, def_bm, TopInfo { parent_pat: Some(&pat), ..ti });
+                self.check_pat(subpat, field_ty, def_bm, TopInfo { parent_pat: Some(pat), ..ti });
 
                 self.tcx.check_stability(
                     variant.fields[i].did,
@@ -1151,7 +1151,7 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
         let mut expected_len = elements.len();
         if ddpos.is_some() {
             // Require known type only when `..` is present.
-            if let ty::Tuple(ref tys) = self.structurally_resolved_type(span, expected).kind() {
+            if let ty::Tuple(tys) = self.structurally_resolved_type(span, expected).kind() {
                 expected_len = tys.len();
             }
         }
@@ -1172,12 +1172,12 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
             // further errors being emitted when using the bindings. #50333
             let element_tys_iter = (0..max_len).map(|_| tcx.ty_error());
             for (_, elem) in elements.iter().enumerate_and_adjust(max_len, ddpos) {
-                self.check_pat(elem, &tcx.ty_error(), def_bm, ti);
+                self.check_pat(elem, tcx.ty_error(), def_bm, ti);
             }
             tcx.mk_tup(element_tys_iter)
         } else {
             for (i, elem) in elements.iter().enumerate_and_adjust(max_len, ddpos) {
-                self.check_pat(elem, &element_tys[i].expect_ty(), def_bm, ti);
+                self.check_pat(elem, element_tys[i].expect_ty(), def_bm, ti);
             }
             pat_ty
         }
@@ -1240,14 +1240,14 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
                 }
             };
 
-            self.check_pat(&field.pat, field_ty, def_bm, TopInfo { parent_pat: Some(&pat), ..ti });
+            self.check_pat(field.pat, field_ty, def_bm, TopInfo { parent_pat: Some(pat), ..ti });
         }
 
         let mut unmentioned_fields = variant
             .fields
             .iter()
             .map(|field| (field, field.ident.normalize_to_macros_2_0()))
-            .filter(|(_, ident)| !used_fields.contains_key(&ident))
+            .filter(|(_, ident)| !used_fields.contains_key(ident))
             .collect::<Vec<_>>();
 
         let inexistent_fields_err = if !(inexistent_fields.is_empty() || variant.is_recovered()) {
@@ -1290,13 +1290,13 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
                 self.non_exhaustive_reachable_pattern(pat, &accessible_unmentioned_fields, adt_ty)
             } else if !etc {
                 if accessible_unmentioned_fields.is_empty() {
-                    unmentioned_err = Some(self.error_no_accessible_fields(pat, &fields));
+                    unmentioned_err = Some(self.error_no_accessible_fields(pat, fields));
                 } else {
                     unmentioned_err = Some(self.error_unmentioned_fields(
                         pat,
                         &accessible_unmentioned_fields,
                         accessible_unmentioned_fields.len() != unmentioned_fields.len(),
-                        &fields,
+                        fields,
                     ));
                 }
             }
@@ -1763,7 +1763,7 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
         ti: TopInfo<'tcx>,
     ) -> Ty<'tcx> {
         let tcx = self.tcx;
-        let (box_ty, inner_ty) = if self.check_dereferenceable(span, expected, &inner) {
+        let (box_ty, inner_ty) = if self.check_dereferenceable(span, expected, inner) {
             // Here, `demand::subtype` is good enough, but I don't
             // think any errors can be introduced by using `demand::eqtype`.
             let inner_ty = self.next_ty_var(TypeVariableOrigin {
@@ -1777,7 +1777,7 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
             let err = tcx.ty_error();
             (err, err)
         };
-        self.check_pat(&inner, inner_ty, def_bm, ti);
+        self.check_pat(inner, inner_ty, def_bm, ti);
         box_ty
     }
 
@@ -1792,7 +1792,7 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
     ) -> Ty<'tcx> {
         let tcx = self.tcx;
         let expected = self.shallow_resolve(expected);
-        let (rptr_ty, inner_ty) = if self.check_dereferenceable(pat.span, expected, &inner) {
+        let (rptr_ty, inner_ty) = if self.check_dereferenceable(pat.span, expected, inner) {
             // `demand::subtype` would be good enough, but using `eqtype` turns
             // out to be equally general. See (note_1) for details.
 
@@ -1814,7 +1814,7 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
                     // Look for a case like `fn foo(&foo: u32)` and suggest
                     // `fn foo(foo: &u32)`
                     if let Some(mut err) = err {
-                        self.borrow_pat_suggestion(&mut err, &pat, &inner, &expected);
+                        self.borrow_pat_suggestion(&mut err, pat, inner, expected);
                         err.emit();
                     }
                     (rptr_ty, inner_ty)
@@ -1824,7 +1824,7 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
             let err = tcx.ty_error();
             (err, err)
         };
-        self.check_pat(&inner, inner_ty, def_bm, TopInfo { parent_pat: Some(&pat), ..ti });
+        self.check_pat(inner, inner_ty, def_bm, TopInfo { parent_pat: Some(pat), ..ti });
         rptr_ty
     }
 
@@ -1880,15 +1880,15 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
 
         // Type check all the patterns before `slice`.
         for elt in before {
-            self.check_pat(&elt, element_ty, def_bm, ti);
+            self.check_pat(elt, element_ty, def_bm, ti);
         }
         // Type check the `slice`, if present, against its expected type.
         if let Some(slice) = slice {
-            self.check_pat(&slice, opt_slice_ty.unwrap(), def_bm, ti);
+            self.check_pat(slice, opt_slice_ty.unwrap(), def_bm, ti);
         }
         // Type check the elements after `slice`, if present.
         for elt in after {
-            self.check_pat(&elt, element_ty, def_bm, ti);
+            self.check_pat(elt, element_ty, def_bm, ti);
         }
         inferred
     }
diff --git a/compiler/rustc_typeck/src/check/place_op.rs b/compiler/rustc_typeck/src/check/place_op.rs
index 64775d7aba9..7cd7fc1681f 100644
--- a/compiler/rustc_typeck/src/check/place_op.rs
+++ b/compiler/rustc_typeck/src/check/place_op.rs
@@ -288,7 +288,7 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
         | hir::ExprKind::Index(ref expr, _)
         | hir::ExprKind::Unary(hir::UnOp::Deref, ref expr) = exprs.last().unwrap().kind
         {
-            exprs.push(&expr);
+            exprs.push(expr);
         }
 
         debug!("convert_place_derefs_to_mutable: exprs={:?}", exprs);
@@ -350,10 +350,10 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
             }
 
             match expr.kind {
-                hir::ExprKind::Index(ref base_expr, ..) => {
+                hir::ExprKind::Index(base_expr, ..) => {
                     self.convert_place_op_to_mutable(PlaceOp::Index, expr, base_expr);
                 }
-                hir::ExprKind::Unary(hir::UnOp::Deref, ref base_expr) => {
+                hir::ExprKind::Unary(hir::UnOp::Deref, base_expr) => {
                     self.convert_place_op_to_mutable(PlaceOp::Deref, expr, base_expr);
                 }
                 _ => {}
diff --git a/compiler/rustc_typeck/src/check/regionck.rs b/compiler/rustc_typeck/src/check/regionck.rs
index 134604a0e32..693246a3433 100644
--- a/compiler/rustc_typeck/src/check/regionck.rs
+++ b/compiler/rustc_typeck/src/check/regionck.rs
@@ -190,7 +190,7 @@ pub struct RegionCtxt<'a, 'tcx> {
 impl<'a, 'tcx> Deref for RegionCtxt<'a, 'tcx> {
     type Target = FnCtxt<'a, 'tcx>;
     fn deref(&self) -> &Self::Target {
-        &self.fcx
+        self.fcx
     }
 }
 
@@ -292,7 +292,7 @@ impl<'a, 'tcx> RegionCtxt<'a, 'tcx> {
 
         self.outlives_environment.add_implied_bounds(self.fcx, fn_sig_tys, body_id.hir_id, span);
         self.outlives_environment.save_implied_bounds(body_id.hir_id);
-        self.link_fn_params(&body.params);
+        self.link_fn_params(body.params);
         self.visit_body(body);
         self.visit_region_obligations(body_id.hir_id);
 
@@ -379,13 +379,13 @@ impl<'a, 'tcx> Visitor<'tcx> for RegionCtxt<'a, 'tcx> {
 
     fn visit_arm(&mut self, arm: &'tcx hir::Arm<'tcx>) {
         // see above
-        self.constrain_bindings_in_pat(&arm.pat);
+        self.constrain_bindings_in_pat(arm.pat);
         intravisit::walk_arm(self, arm);
     }
 
     fn visit_local(&mut self, l: &'tcx hir::Local<'tcx>) {
         // see above
-        self.constrain_bindings_in_pat(&l.pat);
+        self.constrain_bindings_in_pat(l.pat);
         self.link_local(l);
         intravisit::walk_local(self, l);
     }
@@ -407,13 +407,13 @@ impl<'a, 'tcx> Visitor<'tcx> for RegionCtxt<'a, 'tcx> {
 
         match expr.kind {
             hir::ExprKind::AddrOf(hir::BorrowKind::Ref, m, ref base) => {
-                self.link_addr_of(expr, m, &base);
+                self.link_addr_of(expr, m, base);
 
                 intravisit::walk_expr(self, expr);
             }
 
-            hir::ExprKind::Match(ref discr, ref arms, _) => {
-                self.link_match(&discr, &arms[..]);
+            hir::ExprKind::Match(ref discr, arms, _) => {
+                self.link_match(discr, &arms[..]);
 
                 intravisit::walk_expr(self, expr);
             }
@@ -448,7 +448,7 @@ impl<'a, 'tcx> RegionCtxt<'a, 'tcx> {
         let mut place = self.with_mc(|mc| mc.cat_expr_unadjusted(expr))?;
 
         let typeck_results = self.typeck_results.borrow();
-        let adjustments = typeck_results.expr_adjustments(&expr);
+        let adjustments = typeck_results.expr_adjustments(expr);
         if adjustments.is_empty() {
             return Ok(place);
         }
@@ -475,7 +475,7 @@ impl<'a, 'tcx> RegionCtxt<'a, 'tcx> {
                 self.link_autoref(expr, &place, autoref);
             }
 
-            place = self.with_mc(|mc| mc.cat_expr_adjusted(expr, place, &adjustment))?;
+            place = self.with_mc(|mc| mc.cat_expr_adjusted(expr, place, adjustment))?;
         }
 
         Ok(place)
@@ -540,10 +540,10 @@ impl<'a, 'tcx> RegionCtxt<'a, 'tcx> {
             None => {
                 return;
             }
-            Some(ref expr) => &**expr,
+            Some(expr) => &*expr,
         };
         let discr_cmt = ignore_err!(self.with_mc(|mc| mc.cat_expr(init_expr)));
-        self.link_pattern(discr_cmt, &local.pat);
+        self.link_pattern(discr_cmt, local.pat);
     }
 
     /// Computes the guarantors for any ref bindings in a match and
@@ -554,7 +554,7 @@ impl<'a, 'tcx> RegionCtxt<'a, 'tcx> {
         let discr_cmt = ignore_err!(self.with_mc(|mc| mc.cat_expr(discr)));
         debug!("discr_cmt={:?}", discr_cmt);
         for arm in arms {
-            self.link_pattern(discr_cmt.clone(), &arm.pat);
+            self.link_pattern(discr_cmt.clone(), arm.pat);
         }
     }
 
@@ -567,7 +567,7 @@ impl<'a, 'tcx> RegionCtxt<'a, 'tcx> {
             let param_cmt =
                 self.with_mc(|mc| mc.cat_rvalue(param.hir_id, param.pat.span, param_ty));
             debug!("param_ty={:?} param_cmt={:?} param={:?}", param_ty, param_cmt, param);
-            self.link_pattern(param_cmt, &param.pat);
+            self.link_pattern(param_cmt, param.pat);
         }
     }
 
@@ -582,7 +582,7 @@ impl<'a, 'tcx> RegionCtxt<'a, 'tcx> {
                     if let Some(ty::BindByReference(mutbl)) =
                         mc.typeck_results.extract_binding_mode(self.tcx.sess, *hir_id, *span)
                     {
-                        self.link_region_from_node_type(*span, *hir_id, mutbl, &sub_cmt);
+                        self.link_region_from_node_type(*span, *hir_id, mutbl, sub_cmt);
                     }
                 }
             })
diff --git a/compiler/rustc_typeck/src/check/upvar.rs b/compiler/rustc_typeck/src/check/upvar.rs
index 1f2ccffa6f2..56547c82baf 100644
--- a/compiler/rustc_typeck/src/check/upvar.rs
+++ b/compiler/rustc_typeck/src/check/upvar.rs
@@ -790,7 +790,7 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
                             // This is a multi-line closure with just a `{` on the first line,
                             // so we put the `let` on its own line.
                             // We take the indentation from the next non-empty line.
-                            let line2 = lines.filter(|line| !line.is_empty()).next().unwrap_or_default();
+                            let line2 = lines.find(|line| !line.is_empty()).unwrap_or_default();
                             let indent = line2.split_once(|c: char| !c.is_whitespace()).unwrap_or_default().0;
                             diagnostics_builder.span_suggestion(
                                 closure_body_span.with_lo(closure_body_span.lo() + BytePos::from_usize(line1.len())).shrink_to_lo(),
@@ -844,14 +844,14 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
     ) -> String {
         let mut reasons = String::new();
 
-        if auto_trait_reasons.len() > 0 {
+        if !auto_trait_reasons.is_empty() {
             reasons = format!(
                 "{} trait implementation for closure",
                 auto_trait_reasons.clone().into_iter().collect::<Vec<&str>>().join(", ")
             );
         }
 
-        if auto_trait_reasons.len() > 0 && drop_reason {
+        if !auto_trait_reasons.is_empty() && drop_reason {
             reasons = format!("{} and ", reasons);
         }
 
@@ -885,13 +885,7 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
         let auto_traits =
             vec!["`Clone`", "`Sync`", "`Send`", "`Unpin`", "`UnwindSafe`", "`RefUnwindSafe`"];
 
-        let root_var_min_capture_list = if let Some(root_var_min_capture_list) =
-            min_captures.and_then(|m| m.get(&var_hir_id))
-        {
-            root_var_min_capture_list
-        } else {
-            return None;
-        };
+        let root_var_min_capture_list = min_captures.and_then(|m| m.get(&var_hir_id))?;
 
         let ty = self.infcx.resolve_vars_if_possible(self.node_ty(var_hir_id));
 
@@ -966,14 +960,14 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
                 }
             }
 
-            if capture_problems.len() > 0 {
+            if !capture_problems.is_empty() {
                 problematic_captures.insert(
                     (capture.info.path_expr_id, capture.to_string(self.tcx)),
                     capture_problems,
                 );
             }
         }
-        if problematic_captures.len() > 0 {
+        if !problematic_captures.is_empty() {
             return Some(problematic_captures);
         }
         None
@@ -1042,7 +1036,7 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
         let is_moved = !projections_list.is_empty();
 
         let is_not_completely_captured =
-            root_var_min_capture_list.iter().any(|capture| capture.place.projections.len() > 0);
+            root_var_min_capture_list.iter().any(|capture| !capture.place.projections.is_empty());
 
         if is_moved
             && is_not_completely_captured
@@ -1056,7 +1050,7 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
             return Some(diagnostics_info);
         }
 
-        return None;
+        None
     }
 
     /// Figures out the list of root variables (and their types) that aren't completely
@@ -1152,7 +1146,7 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
                 ));
             }
 
-            if capture_diagnostic.len() > 0 {
+            if !capture_diagnostic.is_empty() {
                 need_migrations.push((var_hir_id, responsible_captured_hir_ids));
             }
         }
@@ -1857,10 +1851,10 @@ impl<'a, 'tcx> euv::Delegate<'tcx> for InferBorrowKind<'a, 'tcx> {
     #[instrument(skip(self), level = "debug")]
     fn consume(&mut self, place_with_id: &PlaceWithHirId<'tcx>, diag_expr_id: hir::HirId) {
         if !self.capture_information.contains_key(&place_with_id.place) {
-            self.init_capture_info_for_place(&place_with_id, diag_expr_id);
+            self.init_capture_info_for_place(place_with_id, diag_expr_id);
         }
 
-        self.adjust_upvar_borrow_kind_for_consume(&place_with_id, diag_expr_id);
+        self.adjust_upvar_borrow_kind_for_consume(place_with_id, diag_expr_id);
     }
 
     #[instrument(skip(self), level = "debug")]
@@ -1997,7 +1991,7 @@ fn restrict_capture_precision<'tcx>(
         }
     }
 
-    return (place, curr_mode);
+    (place, curr_mode)
 }
 
 /// Truncate deref of any reference.
@@ -2066,7 +2060,7 @@ fn construct_capture_kind_reason_string(
     place: &Place<'tcx>,
     capture_info: &ty::CaptureInfo<'tcx>,
 ) -> String {
-    let place_str = construct_place_string(tcx, &place);
+    let place_str = construct_place_string(tcx, place);
 
     let capture_kind_str = match capture_info.capture_kind {
         ty::UpvarCapture::ByValue(_) => "ByValue".into(),
@@ -2077,7 +2071,7 @@ fn construct_capture_kind_reason_string(
 }
 
 fn construct_path_string(tcx: TyCtxt<'_>, place: &Place<'tcx>) -> String {
-    let place_str = construct_place_string(tcx, &place);
+    let place_str = construct_place_string(tcx, place);
 
     format!("{} used here", place_str)
 }
@@ -2087,7 +2081,7 @@ fn construct_capture_info_string(
     place: &Place<'tcx>,
     capture_info: &ty::CaptureInfo<'tcx>,
 ) -> String {
-    let place_str = construct_place_string(tcx, &place);
+    let place_str = construct_place_string(tcx, place);
 
     let capture_kind_str = match capture_info.capture_kind {
         ty::UpvarCapture::ByValue(_) => "ByValue".into(),
diff --git a/compiler/rustc_typeck/src/check/wfcheck.rs b/compiler/rustc_typeck/src/check/wfcheck.rs
index 48204590468..20cf9a75e12 100644
--- a/compiler/rustc_typeck/src/check/wfcheck.rs
+++ b/compiler/rustc_typeck/src/check/wfcheck.rs
@@ -144,20 +144,20 @@ pub fn check_item_well_formed(tcx: TyCtxt<'_>, def_id: LocalDefId) {
         hir::ItemKind::Fn(ref sig, ..) => {
             check_item_fn(tcx, item.hir_id(), item.ident, item.span, sig.decl);
         }
-        hir::ItemKind::Static(ref ty, ..) => {
+        hir::ItemKind::Static(ty, ..) => {
             check_item_type(tcx, item.hir_id(), ty.span, false);
         }
-        hir::ItemKind::Const(ref ty, ..) => {
+        hir::ItemKind::Const(ty, ..) => {
             check_item_type(tcx, item.hir_id(), ty.span, false);
         }
         hir::ItemKind::ForeignMod { items, .. } => {
             for it in items.iter() {
                 let it = tcx.hir().foreign_item(it.id);
                 match it.kind {
-                    hir::ForeignItemKind::Fn(ref decl, ..) => {
+                    hir::ForeignItemKind::Fn(decl, ..) => {
                         check_item_fn(tcx, it.hir_id(), it.ident, it.span, decl)
                     }
-                    hir::ForeignItemKind::Static(ref ty, ..) => {
+                    hir::ForeignItemKind::Static(ty, ..) => {
                         check_item_type(tcx, it.hir_id(), ty.span, true)
                     }
                     hir::ForeignItemKind::Type => (),
@@ -198,7 +198,7 @@ pub fn check_trait_item(tcx: TyCtxt<'_>, def_id: LocalDefId) {
         hir::TraitItemKind::Type(_bounds, Some(ty)) => (None, ty.span),
         _ => (None, trait_item.span),
     };
-    check_object_unsafe_self_trait_by_name(tcx, &trait_item);
+    check_object_unsafe_self_trait_by_name(tcx, trait_item);
     check_associated_item(tcx, trait_item.hir_id(), span, method_sig);
 
     let encl_trait_hir_id = tcx.hir().get_parent_item(hir_id);
@@ -218,7 +218,7 @@ pub fn check_trait_item(tcx: TyCtxt<'_>, def_id: LocalDefId) {
         // We are looking at the `call` function of the `fn` or `fn_mut` lang item.
         // Do some rudimentary sanity checking to avoid an ICE later (issue #83471).
         if let Some(hir::FnSig { decl, span, .. }) = method_sig {
-            if let &[self_ty, _] = &decl.inputs {
+            if let [self_ty, _] = decl.inputs {
                 if !matches!(self_ty.kind, hir::TyKind::Rptr(_, _)) {
                     tcx.sess
                         .struct_span_err(
@@ -473,7 +473,7 @@ fn check_associated_item(
                     item.def_id,
                     &mut implied_bounds,
                 );
-                check_method_receiver(fcx, hir_sig, &item, self_ty);
+                check_method_receiver(fcx, hir_sig, item, self_ty);
             }
             ty::AssocKind::Type => {
                 if let ty::AssocItemContainer::TraitContainer(_) = item.container {
@@ -794,7 +794,7 @@ fn check_where_clauses<'tcx, 'fcx>(
     for param in &generics.params {
         match param.kind {
             GenericParamDefKind::Type { .. } => {
-                if is_our_default(&param) {
+                if is_our_default(param) {
                     let ty = tcx.type_of(param.def_id);
                     // Ignore dependent defaults -- that is, where the default of one type
                     // parameter includes another (e.g., `<T, U = T>`). In those cases, we can't
@@ -809,7 +809,7 @@ fn check_where_clauses<'tcx, 'fcx>(
                 }
             }
             GenericParamDefKind::Const { .. } => {
-                if is_our_default(&param) {
+                if is_our_default(param) {
                     // FIXME(const_generics_defaults): This
                     // is incorrect when dealing with unused substs, for example
                     // for `struct Foo<const N: usize, const M: usize = { 1 - 2 }>`
diff --git a/compiler/rustc_typeck/src/check/writeback.rs b/compiler/rustc_typeck/src/check/writeback.rs
index 2c0d926dd01..d951df94dcf 100644
--- a/compiler/rustc_typeck/src/check/writeback.rs
+++ b/compiler/rustc_typeck/src/check/writeback.rs
@@ -140,7 +140,7 @@ impl<'cx, 'tcx> WritebackCx<'cx, 'tcx> {
     // operating on scalars, we clear the overload.
     fn fix_scalar_builtin_expr(&mut self, e: &hir::Expr<'_>) {
         match e.kind {
-            hir::ExprKind::Unary(hir::UnOp::Neg | hir::UnOp::Not, ref inner) => {
+            hir::ExprKind::Unary(hir::UnOp::Neg | hir::UnOp::Not, inner) => {
                 let inner_ty = self.fcx.node_ty(inner.hir_id);
                 let inner_ty = self.fcx.resolve_vars_if_possible(inner_ty);
 
@@ -150,8 +150,7 @@ impl<'cx, 'tcx> WritebackCx<'cx, 'tcx> {
                     typeck_results.node_substs_mut().remove(e.hir_id);
                 }
             }
-            hir::ExprKind::Binary(ref op, ref lhs, ref rhs)
-            | hir::ExprKind::AssignOp(ref op, ref lhs, ref rhs) => {
+            hir::ExprKind::Binary(ref op, lhs, rhs) | hir::ExprKind::AssignOp(ref op, lhs, rhs) => {
                 let lhs_ty = self.fcx.node_ty(lhs.hir_id);
                 let lhs_ty = self.fcx.resolve_vars_if_possible(lhs_ty);
 
@@ -198,7 +197,7 @@ impl<'cx, 'tcx> WritebackCx<'cx, 'tcx> {
 
             // All valid indexing looks like this; might encounter non-valid indexes at this point.
             let base_ty = typeck_results
-                .expr_ty_adjusted_opt(&base)
+                .expr_ty_adjusted_opt(base)
                 .map(|t| self.fcx.resolve_vars_if_possible(t).kind());
             if base_ty.is_none() {
                 // When encountering `return [0][0]` outside of a `fn` body we can encounter a base
@@ -207,7 +206,7 @@ impl<'cx, 'tcx> WritebackCx<'cx, 'tcx> {
                 self.tcx().sess.delay_span_bug(e.span, &format!("bad base: `{:?}`", base));
             }
             if let Some(ty::Ref(_, base_ty, _)) = base_ty {
-                let index_ty = typeck_results.expr_ty_adjusted_opt(&index).unwrap_or_else(|| {
+                let index_ty = typeck_results.expr_ty_adjusted_opt(index).unwrap_or_else(|| {
                     // When encountering `return [0][0]` outside of a `fn` body we would attempt
                     // to access an unexistend index. We assume that more relevant errors will
                     // already have been emitted, so we only gate on this with an ICE if no
diff --git a/compiler/rustc_typeck/src/check_unused.rs b/compiler/rustc_typeck/src/check_unused.rs
index cb127880c62..59ae08cbaec 100644
--- a/compiler/rustc_typeck/src/check_unused.rs
+++ b/compiler/rustc_typeck/src/check_unused.rs
@@ -26,7 +26,7 @@ impl ItemLikeVisitor<'v> for CheckVisitor<'tcx> {
         if item.vis.node.is_pub() || item.span.is_dummy() {
             return;
         }
-        if let hir::ItemKind::Use(ref path, _) = item.kind {
+        if let hir::ItemKind::Use(path, _) = item.kind {
             self.check_import(item.item_id(), path.span);
         }
     }
diff --git a/compiler/rustc_typeck/src/coherence/inherent_impls.rs b/compiler/rustc_typeck/src/coherence/inherent_impls.rs
index f3fe09ac003..4b13dae056a 100644
--- a/compiler/rustc_typeck/src/coherence/inherent_impls.rs
+++ b/compiler/rustc_typeck/src/coherence/inherent_impls.rs
@@ -57,7 +57,7 @@ impl ItemLikeVisitor<'v> for InherentCollect<'tcx> {
             ty::Foreign(did) => {
                 self.check_def_id(item, did);
             }
-            ty::Dynamic(ref data, ..) if data.principal_def_id().is_some() => {
+            ty::Dynamic(data, ..) if data.principal_def_id().is_some() => {
                 self.check_def_id(item, data.principal_def_id().unwrap());
             }
             ty::Dynamic(..) => {
@@ -411,7 +411,7 @@ impl InherentCollect<'tcx> {
                 // OK
             }
             _ => {
-                let to_implement = if assoc_items.len() == 0 {
+                let to_implement = if assoc_items.is_empty() {
                     String::new()
                 } else {
                     let plural = assoc_items.len() > 1;
diff --git a/compiler/rustc_typeck/src/coherence/inherent_impls_overlap.rs b/compiler/rustc_typeck/src/coherence/inherent_impls_overlap.rs
index 1c36335be81..b91b3d6e023 100644
--- a/compiler/rustc_typeck/src/coherence/inherent_impls_overlap.rs
+++ b/compiler/rustc_typeck/src/coherence/inherent_impls_overlap.rs
@@ -188,7 +188,7 @@ impl ItemLikeVisitor<'v> for InherentOverlapChecker<'tcx> {
                             .collect::<FxHashSet<usize>>();
                         match ids.len() {
                             0 | 1 => {
-                                let id_to_set = if ids.len() == 0 {
+                                let id_to_set = if ids.is_empty() {
                                     // Create a new connected region
                                     let region = ConnectedRegion {
                                         idents: idents_to_add,
diff --git a/compiler/rustc_typeck/src/coherence/mod.rs b/compiler/rustc_typeck/src/coherence/mod.rs
index 7ac26a31872..079604f128d 100644
--- a/compiler/rustc_typeck/src/coherence/mod.rs
+++ b/compiler/rustc_typeck/src/coherence/mod.rs
@@ -221,7 +221,7 @@ fn check_object_overlap<'tcx>(
     }
 
     // check for overlap with the automatic `impl Trait for dyn Trait`
-    if let ty::Dynamic(ref data, ..) = trait_ref.self_ty().kind() {
+    if let ty::Dynamic(data, ..) = trait_ref.self_ty().kind() {
         // This is something like impl Trait1 for Trait2. Illegal
         // if Trait1 is a supertrait of Trait2 or Trait2 is not object safe.
 
diff --git a/compiler/rustc_typeck/src/collect.rs b/compiler/rustc_typeck/src/collect.rs
index 51f9f459af1..f21c5c760ea 100644
--- a/compiler/rustc_typeck/src/collect.rs
+++ b/compiler/rustc_typeck/src/collect.rs
@@ -199,20 +199,16 @@ crate fn placeholder_type_error(
                 let parent_id = tcx.hir().get_parent_node(hir_ty.hir_id);
                 let parent_node = tcx.hir().get(parent_id);
 
-                is_const_or_static = match parent_node {
+                is_const_or_static = matches!(
+                    parent_node,
                     Node::Item(&hir::Item {
                         kind: hir::ItemKind::Const(..) | hir::ItemKind::Static(..),
                         ..
-                    })
-                    | Node::TraitItem(&hir::TraitItem {
+                    }) | Node::TraitItem(&hir::TraitItem {
                         kind: hir::TraitItemKind::Const(..),
                         ..
-                    })
-                    | Node::ImplItem(&hir::ImplItem {
-                        kind: hir::ImplItemKind::Const(..), ..
-                    }) => true,
-                    _ => false,
-                };
+                    }) | Node::ImplItem(&hir::ImplItem { kind: hir::ImplItemKind::Const(..), .. })
+                );
             }
         }
 
@@ -681,10 +677,10 @@ impl ItemCtxt<'tcx> {
                 _ => None,
             })
             .flat_map(|bp| {
-                let bt = if is_param(self.tcx, &bp.bounded_ty, param_id) {
+                let bt = if is_param(self.tcx, bp.bounded_ty, param_id) {
                     Some(ty)
                 } else if !only_self_bounds.0 {
-                    Some(self.to_ty(&bp.bounded_ty))
+                    Some(self.to_ty(bp.bounded_ty))
                 } else {
                     None
                 };
@@ -723,7 +719,7 @@ impl ItemCtxt<'tcx> {
 /// `ast_ty_to_ty`, because we want to avoid triggering an all-out
 /// conversion of the type to avoid inducing unnecessary cycles.
 fn is_param(tcx: TyCtxt<'_>, ast_ty: &hir::Ty<'_>, param_id: hir::HirId) -> bool {
-    if let hir::TyKind::Path(hir::QPath::Resolved(None, ref path)) = ast_ty.kind {
+    if let hir::TyKind::Path(hir::QPath::Resolved(None, path)) = ast_ty.kind {
         match path.res {
             Res::SelfTy(Some(def_id), None) | Res::Def(DefKind::TyParam, def_id) => {
                 def_id == tcx.hir().local_def_id(param_id).to_def_id()
@@ -776,7 +772,7 @@ fn convert_item(tcx: TyCtxt<'_>, item_id: hir::ItemId) {
             tcx.ensure().generics_of(def_id);
             tcx.ensure().type_of(def_id);
             tcx.ensure().predicates_of(def_id);
-            convert_enum_variant_types(tcx, def_id.to_def_id(), &enum_definition.variants);
+            convert_enum_variant_types(tcx, def_id.to_def_id(), enum_definition.variants);
         }
         hir::ItemKind::Impl { .. } => {
             tcx.ensure().generics_of(def_id);
@@ -1153,11 +1149,11 @@ fn super_predicates_that_define_assoc_type(
             <dyn AstConv<'_>>::compute_bounds_that_match_assoc_type(
                 &icx,
                 self_param_ty,
-                &bounds,
+                bounds,
                 assoc_name,
             )
         } else {
-            <dyn AstConv<'_>>::compute_bounds(&icx, self_param_ty, &bounds)
+            <dyn AstConv<'_>>::compute_bounds(&icx, self_param_ty, bounds)
         };
 
         let superbounds1 = superbounds1.predicates(tcx, self_param_ty);
@@ -1334,25 +1330,25 @@ fn has_late_bound_regions<'tcx>(tcx: TyCtxt<'tcx>, node: Node<'tcx>) -> Option<S
     match node {
         Node::TraitItem(item) => match item.kind {
             hir::TraitItemKind::Fn(ref sig, _) => {
-                has_late_bound_regions(tcx, &item.generics, &sig.decl)
+                has_late_bound_regions(tcx, &item.generics, sig.decl)
             }
             _ => None,
         },
         Node::ImplItem(item) => match item.kind {
             hir::ImplItemKind::Fn(ref sig, _) => {
-                has_late_bound_regions(tcx, &item.generics, &sig.decl)
+                has_late_bound_regions(tcx, &item.generics, sig.decl)
             }
             _ => None,
         },
         Node::ForeignItem(item) => match item.kind {
-            hir::ForeignItemKind::Fn(ref fn_decl, _, ref generics) => {
+            hir::ForeignItemKind::Fn(fn_decl, _, ref generics) => {
                 has_late_bound_regions(tcx, generics, fn_decl)
             }
             _ => None,
         },
         Node::Item(item) => match item.kind {
             hir::ItemKind::Fn(ref sig, .., ref generics, _) => {
-                has_late_bound_regions(tcx, generics, &sig.decl)
+                has_late_bound_regions(tcx, generics, sig.decl)
             }
             _ => None,
         },
@@ -1374,7 +1370,7 @@ impl<'v> Visitor<'v> for AnonConstInParamTyDetector {
     }
 
     fn visit_generic_param(&mut self, p: &'v hir::GenericParam<'v>) {
-        if let GenericParamKind::Const { ref ty, default: _ } = p.kind {
+        if let GenericParamKind::Const { ty, default: _ } = p.kind {
             let prev = self.in_param_ty;
             self.in_param_ty = true;
             self.visit_ty(ty);
@@ -1587,7 +1583,7 @@ fn generics_of(tcx: TyCtxt<'_>, def_id: DefId) -> ty::Generics {
     let mut own_start = has_self as u32;
     let parent_count = parent_def_id.map_or(0, |def_id| {
         let generics = tcx.generics_of(def_id);
-        assert_eq!(has_self, false);
+        assert!(!has_self);
         parent_has_self = generics.has_self;
         own_start = generics.count() as u32;
         generics.parent_count + generics.params.len()
@@ -1738,9 +1734,9 @@ fn is_suggestable_infer_ty(ty: &hir::Ty<'_>) -> bool {
 }
 
 pub fn get_infer_ret_ty(output: &'hir hir::FnRetTy<'hir>) -> Option<&'hir hir::Ty<'hir>> {
-    if let hir::FnRetTy::Return(ref ty) = output {
+    if let hir::FnRetTy::Return(ty) = output {
         if is_suggestable_infer_ty(ty) {
-            return Some(&**ty);
+            return Some(&*ty);
         }
     }
     None
@@ -1810,8 +1806,8 @@ fn fn_sig(tcx: TyCtxt<'_>, def_id: DefId) -> ty::PolyFnSig<'_> {
                     hir_id,
                     sig.header.unsafety,
                     sig.header.abi,
-                    &sig.decl,
-                    &generics,
+                    sig.decl,
+                    generics,
                     Some(ident.span),
                     None,
                 ),
@@ -1829,15 +1825,13 @@ fn fn_sig(tcx: TyCtxt<'_>, def_id: DefId) -> ty::PolyFnSig<'_> {
             header.unsafety,
             header.abi,
             decl,
-            &generics,
+            generics,
             Some(ident.span),
             None,
         ),
 
         ForeignItem(&hir::ForeignItem {
-            kind: ForeignItemKind::Fn(ref fn_decl, _, _),
-            ident,
-            ..
+            kind: ForeignItemKind::Fn(fn_decl, _, _), ident, ..
         }) => {
             let abi = tcx.hir().get_foreign_abi(hir_id);
             compute_sig_of_foreign_fn_decl(tcx, def_id.to_def_id(), fn_decl, abi, ident)
@@ -2042,9 +2036,7 @@ fn gather_explicit_predicates_of(tcx: TyCtxt<'_>, def_id: DefId) -> ty::GenericP
             match item.kind {
                 ItemKind::Impl(ref impl_) => {
                     if impl_.defaultness.is_default() {
-                        is_default_impl_trait = tcx
-                            .impl_trait_ref(def_id)
-                            .map(|trait_ref| ty::Binder::dummy(trait_ref));
+                        is_default_impl_trait = tcx.impl_trait_ref(def_id).map(ty::Binder::dummy);
                     }
                     &impl_.generics
                 }
@@ -2143,7 +2135,7 @@ fn gather_explicit_predicates_of(tcx: TyCtxt<'_>, def_id: DefId) -> ty::GenericP
             GenericParamKind::Lifetime { .. } => {
                 param.bounds.iter().for_each(|bound| match bound {
                     hir::GenericBound::Outlives(lt) => {
-                        let bound = <dyn AstConv<'_>>::ast_region_to_region(&icx, &lt, None);
+                        let bound = <dyn AstConv<'_>>::ast_region_to_region(&icx, lt, None);
                         let outlives = ty::Binder::dummy(ty::OutlivesPredicate(region, bound));
                         predicates.insert((outlives.to_predicate(tcx), lt.span));
                     }
@@ -2165,12 +2157,12 @@ fn gather_explicit_predicates_of(tcx: TyCtxt<'_>, def_id: DefId) -> ty::GenericP
                 let param_ty = ty::ParamTy::new(index, name).to_ty(tcx);
                 index += 1;
 
-                let mut bounds = <dyn AstConv<'_>>::compute_bounds(&icx, param_ty, &param.bounds);
+                let mut bounds = <dyn AstConv<'_>>::compute_bounds(&icx, param_ty, param.bounds);
                 // Params are implicitly sized unless a `?Sized` bound is found
                 <dyn AstConv<'_>>::add_implicitly_sized(
                     &icx,
                     &mut bounds,
-                    &param.bounds,
+                    param.bounds,
                     Some((param.hir_id, ast_generics.where_clause.predicates)),
                     param.span,
                 );
@@ -2189,7 +2181,7 @@ fn gather_explicit_predicates_of(tcx: TyCtxt<'_>, def_id: DefId) -> ty::GenericP
     for predicate in where_clause.predicates {
         match predicate {
             hir::WherePredicate::BoundPredicate(bound_pred) => {
-                let ty = icx.to_ty(&bound_pred.bounded_ty);
+                let ty = icx.to_ty(bound_pred.bounded_ty);
                 let bound_vars = icx.tcx.late_bound_vars(bound_pred.bounded_ty.hir_id);
 
                 // Keep the type around in a dummy predicate, in case of no bounds.
@@ -2410,7 +2402,7 @@ fn explicit_predicates_of(tcx: TyCtxt<'_>, def_id: DefId) -> ty::GenericPredicat
     } else {
         if matches!(def_kind, DefKind::AnonConst) && tcx.lazy_normalization() {
             let hir_id = tcx.hir().local_def_id_to_hir_id(def_id.expect_local());
-            if let Some(_) = tcx.hir().opt_const_param_default_param_hir_id(hir_id) {
+            if tcx.hir().opt_const_param_default_param_hir_id(hir_id).is_some() {
                 // In `generics_of` we set the generics' parent to be our parent's parent which means that
                 // we lose out on the predicates of our actual parent if we dont return those predicates here.
                 // (See comment in `generics_of` for more information on why the parent shenanigans is necessary)
@@ -2503,10 +2495,10 @@ fn compute_sig_of_foreign_fn_decl<'tcx>(
             }
         };
         for (input, ty) in iter::zip(decl.inputs, fty.inputs().skip_binder()) {
-            check(&input, ty)
+            check(input, ty)
         }
         if let hir::FnRetTy::Return(ref ty) = decl.output {
-            check(&ty, fty.output().skip_binder())
+            check(ty, fty.output().skip_binder())
         }
     }
 
@@ -2561,7 +2553,7 @@ fn from_target_feature(
         let msg = "malformed `target_feature` attribute input";
         let code = "enable = \"..\"".to_owned();
         tcx.sess
-            .struct_span_err(span, &msg)
+            .struct_span_err(span, msg)
             .span_suggestion(span, "must be of the form", code, Applicability::HasPlaceholders)
             .emit();
     };
@@ -2846,7 +2838,7 @@ fn codegen_fn_attrs(tcx: TyCtxt<'_>, id: DefId) -> CodegenFnAttrs {
                 tcx,
                 id,
                 attr,
-                &supported_target_features,
+                supported_target_features,
                 &mut codegen_fn_attrs.target_features,
             );
         } else if attr.has_name(sym::linkage) {
@@ -3113,7 +3105,7 @@ fn codegen_fn_attrs(tcx: TyCtxt<'_>, id: DefId) -> CodegenFnAttrs {
         codegen_fn_attrs.flags |= CodegenFnAttrFlags::RUSTC_STD_INTERNAL_SYMBOL;
     }
     let check_name = |attr: &Attribute, sym| attr.has_name(sym);
-    if let Some(name) = weak_lang_items::link_name(check_name, &attrs) {
+    if let Some(name) = weak_lang_items::link_name(check_name, attrs) {
         codegen_fn_attrs.export_name = Some(name);
         codegen_fn_attrs.link_name = Some(name);
     }
diff --git a/compiler/rustc_typeck/src/collect/item_bounds.rs b/compiler/rustc_typeck/src/collect/item_bounds.rs
index 2bc048ac8a0..26cad8fb180 100644
--- a/compiler/rustc_typeck/src/collect/item_bounds.rs
+++ b/compiler/rustc_typeck/src/collect/item_bounds.rs
@@ -26,9 +26,9 @@ fn associated_type_bounds<'tcx>(
     );
 
     let icx = ItemCtxt::new(tcx, assoc_item_def_id);
-    let mut bounds = <dyn AstConv<'_>>::compute_bounds(&icx, item_ty, &ast_bounds);
+    let mut bounds = <dyn AstConv<'_>>::compute_bounds(&icx, item_ty, ast_bounds);
     // Associated types are implicitly sized unless a `?Sized` bound is found
-    <dyn AstConv<'_>>::add_implicitly_sized(&icx, &mut bounds, &ast_bounds, None, span);
+    <dyn AstConv<'_>>::add_implicitly_sized(&icx, &mut bounds, ast_bounds, None, span);
 
     let trait_def_id = tcx.associated_item(assoc_item_def_id).container.id();
     let trait_predicates = tcx.trait_explicit_predicates_and_bounds(trait_def_id.expect_local());
@@ -64,9 +64,9 @@ fn opaque_type_bounds<'tcx>(
             tcx.mk_opaque(opaque_def_id, InternalSubsts::identity_for_item(tcx, opaque_def_id));
 
         let icx = ItemCtxt::new(tcx, opaque_def_id);
-        let mut bounds = <dyn AstConv<'_>>::compute_bounds(&icx, item_ty, &ast_bounds);
+        let mut bounds = <dyn AstConv<'_>>::compute_bounds(&icx, item_ty, ast_bounds);
         // Opaque types are implicitly sized unless a `?Sized` bound is found
-        <dyn AstConv<'_>>::add_implicitly_sized(&icx, &mut bounds, &ast_bounds, None, span);
+        <dyn AstConv<'_>>::add_implicitly_sized(&icx, &mut bounds, ast_bounds, None, span);
         let bounds = bounds.predicates(tcx, item_ty);
 
         debug!("opaque_type_bounds({}) = {:?}", tcx.def_path_str(opaque_def_id), bounds);
diff --git a/compiler/rustc_typeck/src/collect/type_of.rs b/compiler/rustc_typeck/src/collect/type_of.rs
index 7a14d7f3d28..2e607de1d33 100644
--- a/compiler/rustc_typeck/src/collect/type_of.rs
+++ b/compiler/rustc_typeck/src/collect/type_of.rs
@@ -312,7 +312,7 @@ pub(super) fn type_of(tcx: TyCtxt<'_>, def_id: DefId) -> Ty<'_> {
                 let substs = InternalSubsts::identity_for_item(tcx, def_id.to_def_id());
                 tcx.mk_fn_def(def_id.to_def_id(), substs)
             }
-            TraitItemKind::Const(ref ty, body_id) => body_id
+            TraitItemKind::Const(ty, body_id) => body_id
                 .and_then(|body_id| {
                     if is_suggestable_infer_ty(ty) {
                         Some(infer_placeholder_type(
@@ -323,7 +323,7 @@ pub(super) fn type_of(tcx: TyCtxt<'_>, def_id: DefId) -> Ty<'_> {
                     }
                 })
                 .unwrap_or_else(|| icx.to_ty(ty)),
-            TraitItemKind::Type(_, Some(ref ty)) => icx.to_ty(ty),
+            TraitItemKind::Type(_, Some(ty)) => icx.to_ty(ty),
             TraitItemKind::Type(_, None) => {
                 span_bug!(item.span, "associated type missing default");
             }
@@ -334,14 +334,14 @@ pub(super) fn type_of(tcx: TyCtxt<'_>, def_id: DefId) -> Ty<'_> {
                 let substs = InternalSubsts::identity_for_item(tcx, def_id.to_def_id());
                 tcx.mk_fn_def(def_id.to_def_id(), substs)
             }
-            ImplItemKind::Const(ref ty, body_id) => {
+            ImplItemKind::Const(ty, body_id) => {
                 if is_suggestable_infer_ty(ty) {
                     infer_placeholder_type(tcx, def_id, body_id, ty.span, item.ident, "constant")
                 } else {
                     icx.to_ty(ty)
                 }
             }
-            ImplItemKind::TyAlias(ref ty) => {
+            ImplItemKind::TyAlias(ty) => {
                 if tcx.impl_trait_ref(tcx.hir().get_parent_did(hir_id).to_def_id()).is_none() {
                     check_feature_inherent_assoc_ty(tcx, item.span);
                 }
@@ -352,7 +352,7 @@ pub(super) fn type_of(tcx: TyCtxt<'_>, def_id: DefId) -> Ty<'_> {
 
         Node::Item(item) => {
             match item.kind {
-                ItemKind::Static(ref ty, .., body_id) => {
+                ItemKind::Static(ty, .., body_id) => {
                     if is_suggestable_infer_ty(ty) {
                         infer_placeholder_type(
                             tcx,
@@ -366,7 +366,7 @@ pub(super) fn type_of(tcx: TyCtxt<'_>, def_id: DefId) -> Ty<'_> {
                         icx.to_ty(ty)
                     }
                 }
-                ItemKind::Const(ref ty, body_id) => {
+                ItemKind::Const(ty, body_id) => {
                     if is_suggestable_infer_ty(ty) {
                         infer_placeholder_type(
                             tcx, def_id, body_id, ty.span, item.ident, "constant",
@@ -375,8 +375,8 @@ pub(super) fn type_of(tcx: TyCtxt<'_>, def_id: DefId) -> Ty<'_> {
                         icx.to_ty(ty)
                     }
                 }
-                ItemKind::TyAlias(ref self_ty, _)
-                | ItemKind::Impl(hir::Impl { ref self_ty, .. }) => icx.to_ty(self_ty),
+                ItemKind::TyAlias(self_ty, _)
+                | ItemKind::Impl(hir::Impl { self_ty, .. }) => icx.to_ty(self_ty),
                 ItemKind::Fn(..) => {
                     let substs = InternalSubsts::identity_for_item(tcx, def_id.to_def_id());
                     tcx.mk_fn_def(def_id.to_def_id(), substs)
@@ -395,7 +395,7 @@ pub(super) fn type_of(tcx: TyCtxt<'_>, def_id: DefId) -> Ty<'_> {
                         .mir_borrowck(owner.expect_local())
                         .concrete_opaque_types
                         .get_value_matching(|(key, _)| key.def_id == def_id.to_def_id())
-                        .map(|concrete_ty| *concrete_ty)
+                        .copied()
                         .unwrap_or_else(|| {
                             tcx.sess.delay_span_bug(
                                 DUMMY_SP,
@@ -446,7 +446,7 @@ pub(super) fn type_of(tcx: TyCtxt<'_>, def_id: DefId) -> Ty<'_> {
                 let substs = InternalSubsts::identity_for_item(tcx, def_id.to_def_id());
                 tcx.mk_fn_def(def_id.to_def_id(), substs)
             }
-            ForeignItemKind::Static(ref t, _) => icx.to_ty(t),
+            ForeignItemKind::Static(t, _) => icx.to_ty(t),
             ForeignItemKind::Type => tcx.mk_foreign(def_id.to_def_id()),
         },
 
@@ -460,7 +460,7 @@ pub(super) fn type_of(tcx: TyCtxt<'_>, def_id: DefId) -> Ty<'_> {
             }
         },
 
-        Node::Field(field) => icx.to_ty(&field.ty),
+        Node::Field(field) => icx.to_ty(field.ty),
 
         Node::Expr(&Expr { kind: ExprKind::Closure(.., gen), .. }) => {
             let substs = InternalSubsts::identity_for_item(tcx, def_id.to_def_id());
@@ -685,9 +685,9 @@ fn find_opaque_ty_constraints(tcx: TyCtxt<'_>, def_id: LocalDefId) -> Ty<'_> {
             //
             // requires us to explicitly process `foo()` in order
             // to notice the defining usage of `Blah`.
-            Node::Item(ref it) => locator.visit_item(it),
-            Node::ImplItem(ref it) => locator.visit_impl_item(it),
-            Node::TraitItem(ref it) => locator.visit_trait_item(it),
+            Node::Item(it) => locator.visit_item(it),
+            Node::ImplItem(it) => locator.visit_impl_item(it),
+            Node::TraitItem(it) => locator.visit_trait_item(it),
             other => bug!("{:?} is not a valid scope for an opaque type item", other),
         }
     }
diff --git a/compiler/rustc_typeck/src/constrained_generic_params.rs b/compiler/rustc_typeck/src/constrained_generic_params.rs
index 9b6f0be47ca..88877ad7852 100644
--- a/compiler/rustc_typeck/src/constrained_generic_params.rs
+++ b/compiler/rustc_typeck/src/constrained_generic_params.rs
@@ -206,7 +206,7 @@ pub fn setup_constraining_predicates<'tcx>(
                 // Then the projection only applies if `T` is known, but it still
                 // does not determine `U`.
                 let inputs = parameters_for(tcx, &projection.projection_ty, true);
-                let relies_only_on_inputs = inputs.iter().all(|p| input_parameters.contains(&p));
+                let relies_only_on_inputs = inputs.iter().all(|p| input_parameters.contains(p));
                 if !relies_only_on_inputs {
                     continue;
                 }
diff --git a/compiler/rustc_typeck/src/expr_use_visitor.rs b/compiler/rustc_typeck/src/expr_use_visitor.rs
index b5c4d6ac261..7d0600b99e3 100644
--- a/compiler/rustc_typeck/src/expr_use_visitor.rs
+++ b/compiler/rustc_typeck/src/expr_use_visitor.rs
@@ -124,12 +124,12 @@ impl<'a, 'tcx> ExprUseVisitor<'a, 'tcx> {
     #[instrument(skip(self), level = "debug")]
     pub fn consume_body(&mut self, body: &hir::Body<'_>) {
         for param in body.params {
-            let param_ty = return_if_err!(self.mc.pat_ty_adjusted(&param.pat));
+            let param_ty = return_if_err!(self.mc.pat_ty_adjusted(param.pat));
             debug!("consume_body: param_ty = {:?}", param_ty);
 
             let param_place = self.mc.cat_rvalue(param.hir_id, param.pat.span, param_ty);
 
-            self.walk_irrefutable_pat(&param_place, &param.pat);
+            self.walk_irrefutable_pat(&param_place, param.pat);
         }
 
         self.consume_expr(&body.value);
@@ -145,7 +145,7 @@ impl<'a, 'tcx> ExprUseVisitor<'a, 'tcx> {
 
     fn consume_exprs(&mut self, exprs: &[hir::Expr<'_>]) {
         for expr in exprs {
-            self.consume_expr(&expr);
+            self.consume_expr(expr);
         }
     }
 
@@ -184,57 +184,57 @@ impl<'a, 'tcx> ExprUseVisitor<'a, 'tcx> {
         match expr.kind {
             hir::ExprKind::Path(_) => {}
 
-            hir::ExprKind::Type(ref subexpr, _) => self.walk_expr(subexpr),
+            hir::ExprKind::Type(subexpr, _) => self.walk_expr(subexpr),
 
-            hir::ExprKind::Unary(hir::UnOp::Deref, ref base) => {
+            hir::ExprKind::Unary(hir::UnOp::Deref, base) => {
                 // *base
                 self.select_from_expr(base);
             }
 
-            hir::ExprKind::Field(ref base, _) => {
+            hir::ExprKind::Field(base, _) => {
                 // base.f
                 self.select_from_expr(base);
             }
 
-            hir::ExprKind::Index(ref lhs, ref rhs) => {
+            hir::ExprKind::Index(lhs, rhs) => {
                 // lhs[rhs]
                 self.select_from_expr(lhs);
                 self.consume_expr(rhs);
             }
 
-            hir::ExprKind::Call(ref callee, ref args) => {
+            hir::ExprKind::Call(callee, args) => {
                 // callee(args)
                 self.consume_expr(callee);
                 self.consume_exprs(args);
             }
 
-            hir::ExprKind::MethodCall(.., ref args, _) => {
+            hir::ExprKind::MethodCall(.., args, _) => {
                 // callee.m(args)
                 self.consume_exprs(args);
             }
 
-            hir::ExprKind::Struct(_, ref fields, ref opt_with) => {
+            hir::ExprKind::Struct(_, fields, ref opt_with) => {
                 self.walk_struct_expr(fields, opt_with);
             }
 
-            hir::ExprKind::Tup(ref exprs) => {
+            hir::ExprKind::Tup(exprs) => {
                 self.consume_exprs(exprs);
             }
 
             hir::ExprKind::If(ref cond_expr, ref then_expr, ref opt_else_expr) => {
-                self.consume_expr(&cond_expr);
-                self.consume_expr(&then_expr);
+                self.consume_expr(cond_expr);
+                self.consume_expr(then_expr);
                 if let Some(ref else_expr) = *opt_else_expr {
-                    self.consume_expr(&else_expr);
+                    self.consume_expr(else_expr);
                 }
             }
 
-            hir::ExprKind::Let(ref pat, ref expr, _) => {
-                self.walk_local(expr, pat, |t| t.borrow_expr(&expr, ty::ImmBorrow));
+            hir::ExprKind::Let(pat, ref expr, _) => {
+                self.walk_local(expr, pat, |t| t.borrow_expr(expr, ty::ImmBorrow));
             }
 
             hir::ExprKind::Match(ref discr, arms, _) => {
-                let discr_place = return_if_err!(self.mc.cat_expr(&discr));
+                let discr_place = return_if_err!(self.mc.cat_expr(discr));
 
                 // Matching should not always be considered a use of the place, hence
                 // discr does not necessarily need to be borrowed.
@@ -243,7 +243,7 @@ impl<'a, 'tcx> ExprUseVisitor<'a, 'tcx> {
                 let ExprUseVisitor { ref mc, body_owner: _, delegate: _ } = *self;
                 let mut needs_to_be_read = false;
                 for arm in arms.iter() {
-                    return_if_err!(mc.cat_pattern(discr_place.clone(), &arm.pat, |place, pat| {
+                    return_if_err!(mc.cat_pattern(discr_place.clone(), arm.pat, |place, pat| {
                         match &pat.kind {
                             PatKind::Binding(.., opt_sub_pat) => {
                                 // If the opt_sub_pat is None, than the binding does not count as
@@ -303,7 +303,7 @@ impl<'a, 'tcx> ExprUseVisitor<'a, 'tcx> {
                 }
 
                 if needs_to_be_read {
-                    self.borrow_expr(&discr, ty::ImmBorrow);
+                    self.borrow_expr(discr, ty::ImmBorrow);
                 } else {
                     let closure_def_id = match discr_place.place.base {
                         PlaceBase::Upvar(upvar_id) => Some(upvar_id.closure_expr_id.to_def_id()),
@@ -318,7 +318,7 @@ impl<'a, 'tcx> ExprUseVisitor<'a, 'tcx> {
 
                     // We always want to walk the discriminant. We want to make sure, for instance,
                     // that the discriminant has been initialized.
-                    self.walk_expr(&discr);
+                    self.walk_expr(discr);
                 }
 
                 // treatment of the discriminant is handled while walking the arms.
@@ -327,7 +327,7 @@ impl<'a, 'tcx> ExprUseVisitor<'a, 'tcx> {
                 }
             }
 
-            hir::ExprKind::Array(ref exprs) => {
+            hir::ExprKind::Array(exprs) => {
                 self.consume_exprs(exprs);
             }
 
@@ -336,10 +336,10 @@ impl<'a, 'tcx> ExprUseVisitor<'a, 'tcx> {
                 // make sure that the thing we are pointing out stays valid
                 // for the lifetime `scope_r` of the resulting ptr:
                 let bk = ty::BorrowKind::from_mutbl(m);
-                self.borrow_expr(&base, bk);
+                self.borrow_expr(base, bk);
             }
 
-            hir::ExprKind::InlineAsm(ref asm) => {
+            hir::ExprKind::InlineAsm(asm) => {
                 for (op, _op_sp) in asm.operands {
                     match op {
                         hir::InlineAsmOperand::In { expr, .. }
@@ -360,7 +360,7 @@ impl<'a, 'tcx> ExprUseVisitor<'a, 'tcx> {
                 }
             }
 
-            hir::ExprKind::LlvmInlineAsm(ref ia) => {
+            hir::ExprKind::LlvmInlineAsm(ia) => {
                 for (o, output) in iter::zip(&ia.inner.outputs, ia.outputs_exprs) {
                     if o.is_indirect {
                         self.consume_expr(output);
@@ -368,7 +368,7 @@ impl<'a, 'tcx> ExprUseVisitor<'a, 'tcx> {
                         self.mutate_expr(output);
                     }
                 }
-                self.consume_exprs(&ia.inputs_exprs);
+                self.consume_exprs(ia.inputs_exprs);
             }
 
             hir::ExprKind::Continue(..)
@@ -376,43 +376,43 @@ impl<'a, 'tcx> ExprUseVisitor<'a, 'tcx> {
             | hir::ExprKind::ConstBlock(..)
             | hir::ExprKind::Err => {}
 
-            hir::ExprKind::Loop(ref blk, ..) => {
+            hir::ExprKind::Loop(blk, ..) => {
                 self.walk_block(blk);
             }
 
-            hir::ExprKind::Unary(_, ref lhs) => {
+            hir::ExprKind::Unary(_, lhs) => {
                 self.consume_expr(lhs);
             }
 
-            hir::ExprKind::Binary(_, ref lhs, ref rhs) => {
+            hir::ExprKind::Binary(_, lhs, rhs) => {
                 self.consume_expr(lhs);
                 self.consume_expr(rhs);
             }
 
-            hir::ExprKind::Block(ref blk, _) => {
+            hir::ExprKind::Block(blk, _) => {
                 self.walk_block(blk);
             }
 
             hir::ExprKind::Break(_, ref opt_expr) | hir::ExprKind::Ret(ref opt_expr) => {
-                if let Some(ref expr) = *opt_expr {
+                if let Some(expr) = *opt_expr {
                     self.consume_expr(expr);
                 }
             }
 
-            hir::ExprKind::Assign(ref lhs, ref rhs, _) => {
+            hir::ExprKind::Assign(lhs, rhs, _) => {
                 self.mutate_expr(lhs);
                 self.consume_expr(rhs);
             }
 
-            hir::ExprKind::Cast(ref base, _) => {
+            hir::ExprKind::Cast(base, _) => {
                 self.consume_expr(base);
             }
 
-            hir::ExprKind::DropTemps(ref expr) => {
+            hir::ExprKind::DropTemps(expr) => {
                 self.consume_expr(expr);
             }
 
-            hir::ExprKind::AssignOp(_, ref lhs, ref rhs) => {
+            hir::ExprKind::AssignOp(_, lhs, rhs) => {
                 if self.mc.typeck_results.is_method_call(expr) {
                     self.consume_expr(lhs);
                 } else {
@@ -421,7 +421,7 @@ impl<'a, 'tcx> ExprUseVisitor<'a, 'tcx> {
                 self.consume_expr(rhs);
             }
 
-            hir::ExprKind::Repeat(ref base, _) => {
+            hir::ExprKind::Repeat(base, _) => {
                 self.consume_expr(base);
             }
 
@@ -433,7 +433,7 @@ impl<'a, 'tcx> ExprUseVisitor<'a, 'tcx> {
                 self.consume_expr(base);
             }
 
-            hir::ExprKind::Yield(ref value, _) => {
+            hir::ExprKind::Yield(value, _) => {
                 self.consume_expr(value);
             }
         }
@@ -441,7 +441,7 @@ impl<'a, 'tcx> ExprUseVisitor<'a, 'tcx> {
 
     fn walk_stmt(&mut self, stmt: &hir::Stmt<'_>) {
         match stmt.kind {
-            hir::StmtKind::Local(hir::Local { pat, init: Some(ref expr), .. }) => {
+            hir::StmtKind::Local(hir::Local { pat, init: Some(expr), .. }) => {
                 self.walk_local(expr, pat, |_| {});
             }
 
@@ -453,7 +453,7 @@ impl<'a, 'tcx> ExprUseVisitor<'a, 'tcx> {
             }
 
             hir::StmtKind::Expr(ref expr) | hir::StmtKind::Semi(ref expr) => {
-                self.consume_expr(&expr);
+                self.consume_expr(expr);
             }
         }
     }
@@ -462,8 +462,8 @@ impl<'a, 'tcx> ExprUseVisitor<'a, 'tcx> {
     where
         F: FnMut(&mut Self),
     {
-        self.walk_expr(&expr);
-        let expr_place = return_if_err!(self.mc.cat_expr(&expr));
+        self.walk_expr(expr);
+        let expr_place = return_if_err!(self.mc.cat_expr(expr));
         f(self);
         self.walk_irrefutable_pat(&expr_place, &pat);
     }
@@ -478,7 +478,7 @@ impl<'a, 'tcx> ExprUseVisitor<'a, 'tcx> {
         }
 
         if let Some(ref tail_expr) = blk.expr {
-            self.consume_expr(&tail_expr);
+            self.consume_expr(tail_expr);
         }
     }
 
@@ -489,17 +489,17 @@ impl<'a, 'tcx> ExprUseVisitor<'a, 'tcx> {
     ) {
         // Consume the expressions supplying values for each field.
         for field in fields {
-            self.consume_expr(&field.expr);
+            self.consume_expr(field.expr);
         }
 
         let with_expr = match *opt_with {
-            Some(ref w) => &**w,
+            Some(w) => &*w,
             None => {
                 return;
             }
         };
 
-        let with_place = return_if_err!(self.mc.cat_expr(&with_expr));
+        let with_place = return_if_err!(self.mc.cat_expr(with_expr));
 
         // Select just those fields of the `with`
         // expression that will actually be used
@@ -569,7 +569,7 @@ impl<'a, 'tcx> ExprUseVisitor<'a, 'tcx> {
                 }
             }
             place_with_id =
-                return_if_err!(self.mc.cat_expr_adjusted(expr, place_with_id, &adjustment));
+                return_if_err!(self.mc.cat_expr_adjusted(expr, place_with_id, adjustment));
         }
     }
 
@@ -615,15 +615,15 @@ impl<'a, 'tcx> ExprUseVisitor<'a, 'tcx> {
             FakeReadCause::ForMatchedPlace(closure_def_id),
             discr_place.hir_id,
         );
-        self.walk_pat(discr_place, &arm.pat);
+        self.walk_pat(discr_place, arm.pat);
 
-        if let Some(hir::Guard::If(ref e)) = arm.guard {
+        if let Some(hir::Guard::If(e)) = arm.guard {
             self.consume_expr(e)
         } else if let Some(hir::Guard::IfLet(_, ref e)) = arm.guard {
             self.consume_expr(e)
         }
 
-        self.consume_expr(&arm.body);
+        self.consume_expr(arm.body);
     }
 
     /// Walks a pat that occurs in isolation (i.e., top-level of fn argument or
@@ -836,7 +836,7 @@ fn delegate_consume<'a, 'tcx>(
 ) {
     debug!("delegate_consume(place_with_id={:?})", place_with_id);
 
-    let mode = copy_or_move(&mc, place_with_id);
+    let mode = copy_or_move(mc, place_with_id);
 
     match mode {
         ConsumeMode::Move => delegate.consume(place_with_id, diag_expr_id),
diff --git a/compiler/rustc_typeck/src/lib.rs b/compiler/rustc_typeck/src/lib.rs
index f8714cdc70c..8ff074e2fe5 100644
--- a/compiler/rustc_typeck/src/lib.rs
+++ b/compiler/rustc_typeck/src/lib.rs
@@ -143,7 +143,7 @@ fn require_same_types<'tcx>(
     tcx.infer_ctxt().enter(|ref infcx| {
         let param_env = ty::ParamEnv::empty();
         let mut fulfill_cx = <dyn TraitEngine<'_>>::new(infcx.tcx);
-        match infcx.at(&cause, param_env).eq(expected, actual) {
+        match infcx.at(cause, param_env).eq(expected, actual) {
             Ok(InferOk { obligations, .. }) => {
                 fulfill_cx.register_predicate_obligations(infcx, obligations);
             }
@@ -187,9 +187,11 @@ fn check_main_fn_ty(tcx: TyCtxt<'_>, main_def_id: DefId) {
         let hir_id = tcx.hir().local_def_id_to_hir_id(def_id.expect_local());
         match tcx.hir().find(hir_id) {
             Some(Node::Item(hir::Item { kind: hir::ItemKind::Fn(_, ref generics, _), .. })) => {
-                let generics_param_span =
-                    if !generics.params.is_empty() { Some(generics.span) } else { None };
-                generics_param_span
+                if !generics.params.is_empty() {
+                    Some(generics.span)
+                } else {
+                    None
+                }
             }
             _ => {
                 span_bug!(tcx.def_span(def_id), "main has a non-function type");
diff --git a/compiler/rustc_typeck/src/mem_categorization.rs b/compiler/rustc_typeck/src/mem_categorization.rs
index f876d0f2513..440ce04e61a 100644
--- a/compiler/rustc_typeck/src/mem_categorization.rs
+++ b/compiler/rustc_typeck/src/mem_categorization.rs
@@ -307,13 +307,13 @@ impl<'a, 'tcx> MemCategorizationContext<'a, 'tcx> {
                 if self.typeck_results.is_method_call(expr) {
                     self.cat_overloaded_place(expr, e_base)
                 } else {
-                    let base = self.cat_expr(&e_base)?;
+                    let base = self.cat_expr(e_base)?;
                     self.cat_deref(expr, base)
                 }
             }
 
             hir::ExprKind::Field(ref base, _) => {
-                let base = self.cat_expr(&base)?;
+                let base = self.cat_expr(base)?;
                 debug!("cat_expr(cat_field): id={} expr={:?} base={:?}", expr.hir_id, expr, base);
 
                 let field_idx = self
@@ -340,7 +340,7 @@ impl<'a, 'tcx> MemCategorizationContext<'a, 'tcx> {
                     // dereferencing.
                     self.cat_overloaded_place(expr, base)
                 } else {
-                    let base = self.cat_expr(&base)?;
+                    let base = self.cat_expr(base)?;
                     Ok(self.cat_projection(expr, base, expr_ty, ProjectionKind::Index))
                 }
             }
@@ -350,7 +350,7 @@ impl<'a, 'tcx> MemCategorizationContext<'a, 'tcx> {
                 self.cat_res(expr.hir_id, expr.span, expr_ty, res)
             }
 
-            hir::ExprKind::Type(ref e, _) => self.cat_expr(&e),
+            hir::ExprKind::Type(ref e, _) => self.cat_expr(e),
 
             hir::ExprKind::AddrOf(..)
             | hir::ExprKind::Call(..)
@@ -674,31 +674,31 @@ impl<'a, 'tcx> MemCategorizationContext<'a, 'tcx> {
         op(&place_with_id, pat);
 
         match pat.kind {
-            PatKind::Tuple(ref subpats, dots_pos) => {
+            PatKind::Tuple(subpats, dots_pos) => {
                 // (p1, ..., pN)
                 let total_fields = self.total_fields_in_tuple(pat.hir_id, pat.span)?;
 
                 for (i, subpat) in subpats.iter().enumerate_and_adjust(total_fields, dots_pos) {
-                    let subpat_ty = self.pat_ty_adjusted(&subpat)?;
+                    let subpat_ty = self.pat_ty_adjusted(subpat)?;
                     let projection_kind = ProjectionKind::Field(i as u32, VariantIdx::new(0));
                     let sub_place =
                         self.cat_projection(pat, place_with_id.clone(), subpat_ty, projection_kind);
-                    self.cat_pattern_(sub_place, &subpat, op)?;
+                    self.cat_pattern_(sub_place, subpat, op)?;
                 }
             }
 
-            PatKind::TupleStruct(ref qpath, ref subpats, dots_pos) => {
+            PatKind::TupleStruct(ref qpath, subpats, dots_pos) => {
                 // S(p1, ..., pN)
                 let variant_index = self.variant_index_for_adt(qpath, pat.hir_id, pat.span)?;
                 let total_fields =
                     self.total_fields_in_adt_variant(pat.hir_id, variant_index, pat.span)?;
 
                 for (i, subpat) in subpats.iter().enumerate_and_adjust(total_fields, dots_pos) {
-                    let subpat_ty = self.pat_ty_adjusted(&subpat)?;
+                    let subpat_ty = self.pat_ty_adjusted(subpat)?;
                     let projection_kind = ProjectionKind::Field(i as u32, variant_index);
                     let sub_place =
                         self.cat_projection(pat, place_with_id.clone(), subpat_ty, projection_kind);
-                    self.cat_pattern_(sub_place, &subpat, op)?;
+                    self.cat_pattern_(sub_place, subpat, op)?;
                 }
             }
 
@@ -708,7 +708,7 @@ impl<'a, 'tcx> MemCategorizationContext<'a, 'tcx> {
                 let variant_index = self.variant_index_for_adt(qpath, pat.hir_id, pat.span)?;
 
                 for fp in field_pats {
-                    let field_ty = self.pat_ty_adjusted(&fp.pat)?;
+                    let field_ty = self.pat_ty_adjusted(fp.pat)?;
                     let field_index = self
                         .typeck_results
                         .field_indices()
@@ -722,18 +722,18 @@ impl<'a, 'tcx> MemCategorizationContext<'a, 'tcx> {
                         field_ty,
                         ProjectionKind::Field(field_index as u32, variant_index),
                     );
-                    self.cat_pattern_(field_place, &fp.pat, op)?;
+                    self.cat_pattern_(field_place, fp.pat, op)?;
                 }
             }
 
             PatKind::Or(pats) => {
                 for pat in pats {
-                    self.cat_pattern_(place_with_id.clone(), &pat, op)?;
+                    self.cat_pattern_(place_with_id.clone(), pat, op)?;
                 }
             }
 
             PatKind::Binding(.., Some(ref subpat)) => {
-                self.cat_pattern_(place_with_id, &subpat, op)?;
+                self.cat_pattern_(place_with_id, subpat, op)?;
             }
 
             PatKind::Box(ref subpat) | PatKind::Ref(ref subpat, _) => {
@@ -741,7 +741,7 @@ impl<'a, 'tcx> MemCategorizationContext<'a, 'tcx> {
                 // PatKind::Ref since that information is already contained
                 // in the type.
                 let subplace = self.cat_deref(pat, place_with_id)?;
-                self.cat_pattern_(subplace, &subpat, op)?;
+                self.cat_pattern_(subplace, subpat, op)?;
             }
 
             PatKind::Slice(before, ref slice, after) => {
@@ -759,20 +759,20 @@ impl<'a, 'tcx> MemCategorizationContext<'a, 'tcx> {
                     ProjectionKind::Index,
                 );
                 for before_pat in before {
-                    self.cat_pattern_(elt_place.clone(), &before_pat, op)?;
+                    self.cat_pattern_(elt_place.clone(), before_pat, op)?;
                 }
                 if let Some(ref slice_pat) = *slice {
-                    let slice_pat_ty = self.pat_ty_adjusted(&slice_pat)?;
+                    let slice_pat_ty = self.pat_ty_adjusted(slice_pat)?;
                     let slice_place = self.cat_projection(
                         pat,
                         place_with_id,
                         slice_pat_ty,
                         ProjectionKind::Subslice,
                     );
-                    self.cat_pattern_(slice_place, &slice_pat, op)?;
+                    self.cat_pattern_(slice_place, slice_pat, op)?;
                 }
                 for after_pat in after {
-                    self.cat_pattern_(elt_place.clone(), &after_pat, op)?;
+                    self.cat_pattern_(elt_place.clone(), after_pat, op)?;
                 }
             }
 
diff --git a/compiler/rustc_typeck/src/outlives/explicit.rs b/compiler/rustc_typeck/src/outlives/explicit.rs
index 2ac1a18cffa..bbf31de527e 100644
--- a/compiler/rustc_typeck/src/outlives/explicit.rs
+++ b/compiler/rustc_typeck/src/outlives/explicit.rs
@@ -30,20 +30,20 @@ impl<'tcx> ExplicitPredicatesMap<'tcx> {
             // process predicates and convert to `RequiredPredicates` entry, see below
             for &(predicate, span) in predicates.predicates {
                 match predicate.kind().skip_binder() {
-                    ty::PredicateKind::TypeOutlives(OutlivesPredicate(ref ty, ref reg)) => {
+                    ty::PredicateKind::TypeOutlives(OutlivesPredicate(ty, reg)) => {
                         insert_outlives_predicate(
                             tcx,
-                            (*ty).into(),
+                            ty.into(),
                             reg,
                             span,
                             &mut required_predicates,
                         )
                     }
 
-                    ty::PredicateKind::RegionOutlives(OutlivesPredicate(ref reg1, ref reg2)) => {
+                    ty::PredicateKind::RegionOutlives(OutlivesPredicate(reg1, reg2)) => {
                         insert_outlives_predicate(
                             tcx,
-                            (*reg1).into(),
+                            reg1.into(),
                             reg2,
                             span,
                             &mut required_predicates,
diff --git a/compiler/rustc_typeck/src/outlives/mod.rs b/compiler/rustc_typeck/src/outlives/mod.rs
index 9c6efffdaf0..957ff252519 100644
--- a/compiler/rustc_typeck/src/outlives/mod.rs
+++ b/compiler/rustc_typeck/src/outlives/mod.rs
@@ -22,7 +22,7 @@ fn inferred_outlives_of(tcx: TyCtxt<'_>, item_def_id: DefId) -> &[(ty::Predicate
 
     if matches!(tcx.def_kind(item_def_id), hir::def::DefKind::AnonConst) && tcx.lazy_normalization()
     {
-        if let Some(_) = tcx.hir().opt_const_param_default_param_hir_id(id) {
+        if tcx.hir().opt_const_param_default_param_hir_id(id).is_some() {
             // In `generics_of` we set the generics' parent to be our parent's parent which means that
             // we lose out on the predicates of our actual parent if we dont return those predicates here.
             // (See comment in `generics_of` for more information on why the parent shenanigans is necessary)
diff --git a/compiler/rustc_typeck/src/structured_errors/wrong_number_of_generic_args.rs b/compiler/rustc_typeck/src/structured_errors/wrong_number_of_generic_args.rs
index c2038f4e047..8d3862ffc8f 100644
--- a/compiler/rustc_typeck/src/structured_errors/wrong_number_of_generic_args.rs
+++ b/compiler/rustc_typeck/src/structured_errors/wrong_number_of_generic_args.rs
@@ -293,7 +293,7 @@ impl<'a, 'tcx> WrongNumberOfGenericArgs<'a, 'tcx> {
         &self,
         num_params_to_take: usize,
     ) -> String {
-        let fn_sig = self.tcx.hir().get_if_local(self.def_id).and_then(|node| fn_sig(node));
+        let fn_sig = self.tcx.hir().get_if_local(self.def_id).and_then(fn_sig);
         let is_used_in_input = |def_id| {
             fn_sig.map_or(false, |fn_sig| {
                 fn_sig.decl.inputs.iter().any(|ty| match ty.kind {
diff --git a/compiler/rustc_typeck/src/variance/constraints.rs b/compiler/rustc_typeck/src/variance/constraints.rs
index f5355ea042b..9958a7aace2 100644
--- a/compiler/rustc_typeck/src/variance/constraints.rs
+++ b/compiler/rustc_typeck/src/variance/constraints.rs
@@ -293,7 +293,7 @@ impl<'a, 'tcx> ConstraintContext<'a, 'tcx> {
                 self.add_constraints_from_invariant_substs(current, substs, variance);
             }
 
-            ty::Dynamic(ref data, r) => {
+            ty::Dynamic(data, r) => {
                 // The type `Foo<T+'a>` is contravariant w/r/t `'a`:
                 let contra = self.contravariant(variance);
                 self.add_constraints_from_region(current, r, contra);