`rustc_builtin_macros`: remove `ref` patterns

... and other pattern matching improvements

16 files changed, 176 insertions, 196 deletions

diff --git a/compiler/rustc_builtin_macros/src/alloc_error_handler.rs b/compiler/rustc_builtin_macros/src/alloc_error_handler.rs
index 460175ed2ac..95e38e4b053 100644
--- a/compiler/rustc_builtin_macros/src/alloc_error_handler.rs
+++ b/compiler/rustc_builtin_macros/src/alloc_error_handler.rs
@@ -17,32 +17,23 @@ pub fn expand(
     check_builtin_macro_attribute(ecx, meta_item, sym::alloc_error_handler);
 
     let orig_item = item.clone();
-    let not_function = || {
-        ecx.sess
-            .parse_sess
-            .span_diagnostic
-            .span_err(item.span(), "alloc_error_handler must be a function");
-        vec![orig_item.clone()]
-    };
 
     // Allow using `#[alloc_error_handler]` on an item statement
     // FIXME - if we get deref patterns, use them to reduce duplication here
-    let (item, is_stmt, sig_span) = match &item {
-        Annotatable::Item(item) => match item.kind {
-            ItemKind::Fn(ref fn_kind) => (item, false, ecx.with_def_site_ctxt(fn_kind.sig.span)),
-            _ => return not_function(),
-        },
-        Annotatable::Stmt(stmt) => match &stmt.kind {
-            StmtKind::Item(item_) => match item_.kind {
-                ItemKind::Fn(ref fn_kind) => {
-                    (item_, true, ecx.with_def_site_ctxt(fn_kind.sig.span))
-                }
-                _ => return not_function(),
-            },
-            _ => return not_function(),
-        },
-        _ => return not_function(),
-    };
+    let (item, is_stmt, sig_span) =
+        if let Annotatable::Item(item) = &item
+            && let ItemKind::Fn(fn_kind) = &item.kind
+        {
+            (item, false, ecx.with_def_site_ctxt(fn_kind.sig.span))
+        } else if let Annotatable::Stmt(stmt) = &item
+            && let StmtKind::Item(item) = &stmt.kind
+            && let ItemKind::Fn(fn_kind) = &item.kind
+        {
+            (item, true, ecx.with_def_site_ctxt(fn_kind.sig.span))
+        } else {
+            ecx.sess.parse_sess.span_diagnostic.span_err(item.span(), "alloc_error_handler must be a function");
+            return vec![orig_item.clone()];
+        };
 
     // Generate a bunch of new items using the AllocFnFactory
     let span = ecx.with_def_site_ctxt(item.span);
diff --git a/compiler/rustc_builtin_macros/src/assert/context.rs b/compiler/rustc_builtin_macros/src/assert/context.rs
index d82bc0453f5..93b07801e03 100644
--- a/compiler/rustc_builtin_macros/src/assert/context.rs
+++ b/compiler/rustc_builtin_macros/src/assert/context.rs
@@ -191,19 +191,19 @@ impl<'cx, 'a> Context<'cx, 'a> {
     ///
     /// See [Self::manage_initial_capture] and [Self::manage_try_capture]
     fn manage_cond_expr(&mut self, expr: &mut P<Expr>) {
-        match (*expr).kind {
-            ExprKind::AddrOf(_, mutability, ref mut local_expr) => {
+        match &mut expr.kind {
+            ExprKind::AddrOf(_, mutability, local_expr) => {
                 self.with_is_consumed_management(
                     matches!(mutability, Mutability::Mut),
                     |this| this.manage_cond_expr(local_expr)
                 );
             }
-            ExprKind::Array(ref mut local_exprs) => {
+            ExprKind::Array(local_exprs) => {
                 for local_expr in local_exprs {
                     self.manage_cond_expr(local_expr);
                 }
             }
-            ExprKind::Binary(ref op, ref mut lhs, ref mut rhs) => {
+            ExprKind::Binary(op, lhs, rhs) => {
                 self.with_is_consumed_management(
                     matches!(
                         op.node,
@@ -226,56 +226,56 @@ impl<'cx, 'a> Context<'cx, 'a> {
                     }
                 );
             }
-            ExprKind::Call(_, ref mut local_exprs) => {
+            ExprKind::Call(_, local_exprs) => {
                 for local_expr in local_exprs {
                     self.manage_cond_expr(local_expr);
                 }
             }
-            ExprKind::Cast(ref mut local_expr, _) => {
+            ExprKind::Cast(local_expr, _) => {
                 self.manage_cond_expr(local_expr);
             }
-            ExprKind::Index(ref mut prefix, ref mut suffix) => {
+            ExprKind::Index(prefix, suffix) => {
                 self.manage_cond_expr(prefix);
                 self.manage_cond_expr(suffix);
             }
-            ExprKind::MethodCall(ref mut call) => {
-                for arg in call.args.iter_mut() {
+            ExprKind::MethodCall(call) => {
+                for arg in &mut call.args {
                     self.manage_cond_expr(arg);
                 }
             }
-            ExprKind::Path(_, Path { ref segments, .. }) if let &[ref path_segment] = &segments[..] => {
+            ExprKind::Path(_, Path { segments, .. }) if let [path_segment] = &segments[..] => {
                 let path_ident = path_segment.ident;
                 self.manage_initial_capture(expr, path_ident);
             }
-            ExprKind::Paren(ref mut local_expr) => {
+            ExprKind::Paren(local_expr) => {
                 self.manage_cond_expr(local_expr);
             }
-            ExprKind::Range(ref mut prefix, ref mut suffix, _) => {
-                if let Some(ref mut elem) = prefix {
+            ExprKind::Range(prefix, suffix, _) => {
+                if let Some(elem) = prefix {
                     self.manage_cond_expr(elem);
                 }
-                if let Some(ref mut elem) = suffix {
+                if let Some(elem) = suffix {
                     self.manage_cond_expr(elem);
                 }
             }
-            ExprKind::Repeat(ref mut local_expr, ref mut elem) => {
+            ExprKind::Repeat(local_expr, elem) => {
                 self.manage_cond_expr(local_expr);
                 self.manage_cond_expr(&mut elem.value);
             }
-            ExprKind::Struct(ref mut elem) => {
+            ExprKind::Struct(elem) => {
                 for field in &mut elem.fields {
                     self.manage_cond_expr(&mut field.expr);
                 }
-                if let StructRest::Base(ref mut local_expr) = elem.rest {
+                if let StructRest::Base(local_expr) = &mut elem.rest {
                     self.manage_cond_expr(local_expr);
                 }
             }
-            ExprKind::Tup(ref mut local_exprs) => {
+            ExprKind::Tup(local_exprs) => {
                 for local_expr in local_exprs {
                     self.manage_cond_expr(local_expr);
                 }
             }
-            ExprKind::Unary(un_op, ref mut local_expr) => {
+            ExprKind::Unary(un_op, local_expr) => {
                 self.with_is_consumed_management(
                     matches!(un_op, UnOp::Neg | UnOp::Not),
                     |this| this.manage_cond_expr(local_expr)
diff --git a/compiler/rustc_builtin_macros/src/concat.rs b/compiler/rustc_builtin_macros/src/concat.rs
index d579616ad1b..e2d71825d55 100644
--- a/compiler/rustc_builtin_macros/src/concat.rs
+++ b/compiler/rustc_builtin_macros/src/concat.rs
@@ -20,7 +20,7 @@ pub fn expand_concat(
     for e in es {
         match e.kind {
             ast::ExprKind::Lit(token_lit) => match ast::LitKind::from_token_lit(token_lit) {
-                Ok(ast::LitKind::Str(ref s, _) | ast::LitKind::Float(ref s, _)) => {
+                Ok(ast::LitKind::Str(s, _) | ast::LitKind::Float(s, _)) => {
                     accumulator.push_str(s.as_str());
                 }
                 Ok(ast::LitKind::Char(c)) => {
diff --git a/compiler/rustc_builtin_macros/src/concat_bytes.rs b/compiler/rustc_builtin_macros/src/concat_bytes.rs
index 161e3499584..d1124145dcb 100644
--- a/compiler/rustc_builtin_macros/src/concat_bytes.rs
+++ b/compiler/rustc_builtin_macros/src/concat_bytes.rs
@@ -144,8 +144,8 @@ pub fn expand_concat_bytes(
     let mut missing_literals = vec![];
     let mut has_errors = false;
     for e in es {
-        match e.kind {
-            ast::ExprKind::Array(ref exprs) => {
+        match &e.kind {
+            ast::ExprKind::Array(exprs) => {
                 for expr in exprs {
                     if let Some(elem) =
                         handle_array_element(cx, &mut has_errors, &mut missing_literals, expr)
@@ -154,7 +154,7 @@ pub fn expand_concat_bytes(
                     }
                 }
             }
-            ast::ExprKind::Repeat(ref expr, ref count) => {
+            ast::ExprKind::Repeat(expr, count) => {
                 if let ast::ExprKind::Lit(token_lit) = count.value.kind
                 && let Ok(ast::LitKind::Int(count_val, _)) =
                     ast::LitKind::from_token_lit(token_lit)
@@ -170,7 +170,7 @@ pub fn expand_concat_bytes(
                     cx.span_err(count.value.span, "repeat count is not a positive number");
                 }
             }
-            ast::ExprKind::Lit(token_lit) => match ast::LitKind::from_token_lit(token_lit) {
+            &ast::ExprKind::Lit(token_lit) => match ast::LitKind::from_token_lit(token_lit) {
                 Ok(ast::LitKind::Byte(val)) => {
                     accumulator.push(val);
                 }
@@ -184,7 +184,7 @@ pub fn expand_concat_bytes(
                     has_errors = true;
                 }
             },
-            ast::ExprKind::IncludedBytes(ref bytes) => {
+            ast::ExprKind::IncludedBytes(bytes) => {
                 accumulator.extend_from_slice(bytes);
             }
             ast::ExprKind::Err => {
diff --git a/compiler/rustc_builtin_macros/src/deriving/clone.rs b/compiler/rustc_builtin_macros/src/deriving/clone.rs
index 23b96d4176d..d59b3b8c86d 100644
--- a/compiler/rustc_builtin_macros/src/deriving/clone.rs
+++ b/compiler/rustc_builtin_macros/src/deriving/clone.rs
@@ -32,10 +32,10 @@ pub fn expand_deriving_clone(
     let bounds;
     let substructure;
     let is_simple;
-    match *item {
-        Annotatable::Item(ref annitem) => match annitem.kind {
-            ItemKind::Struct(_, Generics { ref params, .. })
-            | ItemKind::Enum(_, Generics { ref params, .. }) => {
+    match item {
+        Annotatable::Item(annitem) => match &annitem.kind {
+            ItemKind::Struct(_, Generics { params, .. })
+            | ItemKind::Enum(_, Generics { params, .. }) => {
                 let container_id = cx.current_expansion.id.expn_data().parent.expect_local();
                 let has_derive_copy = cx.resolver.has_derive_copy(container_id);
                 if has_derive_copy
@@ -166,13 +166,13 @@ fn cs_clone(
     };
 
     let vdata;
-    match *substr.fields {
-        Struct(vdata_, ref af) => {
+    match substr.fields {
+        Struct(vdata_, af) => {
             ctor_path = cx.path(trait_span, vec![substr.type_ident]);
             all_fields = af;
-            vdata = vdata_;
+            vdata = *vdata_;
         }
-        EnumMatching(.., variant, ref af) => {
+        EnumMatching(.., variant, af) => {
             ctor_path = cx.path(trait_span, vec![substr.type_ident, variant.ident]);
             all_fields = af;
             vdata = &variant.data;
diff --git a/compiler/rustc_builtin_macros/src/deriving/decodable.rs b/compiler/rustc_builtin_macros/src/deriving/decodable.rs
index 6d14875a983..62af02c2bb4 100644
--- a/compiler/rustc_builtin_macros/src/deriving/decodable.rs
+++ b/compiler/rustc_builtin_macros/src/deriving/decodable.rs
@@ -78,11 +78,11 @@ fn decodable_substructure(
     let blkarg = Ident::new(sym::_d, trait_span);
     let blkdecoder = cx.expr_ident(trait_span, blkarg);
 
-    let expr = match *substr.fields {
-        StaticStruct(_, ref summary) => {
-            let nfields = match *summary {
-                Unnamed(ref fields, _) => fields.len(),
-                Named(ref fields) => fields.len(),
+    let expr = match substr.fields {
+        StaticStruct(_, summary) => {
+            let nfields = match summary {
+                Unnamed(fields, _) => fields.len(),
+                Named(fields) => fields.len(),
             };
             let fn_read_struct_field_path: Vec<_> =
                 cx.def_site_path(&[sym::rustc_serialize, sym::Decoder, sym::read_struct_field]);
@@ -119,7 +119,7 @@ fn decodable_substructure(
                 ],
             )
         }
-        StaticEnum(_, ref fields) => {
+        StaticEnum(_, fields) => {
             let variant = Ident::new(sym::i, trait_span);
 
             let mut arms = Vec::with_capacity(fields.len() + 1);
@@ -194,10 +194,10 @@ fn decode_static_fields<F>(
 where
     F: FnMut(&mut ExtCtxt<'_>, Span, Symbol, usize) -> P<Expr>,
 {
-    match *fields {
-        Unnamed(ref fields, is_tuple) => {
+    match fields {
+        Unnamed(fields, is_tuple) => {
             let path_expr = cx.expr_path(outer_pat_path);
-            if !is_tuple {
+            if !*is_tuple {
                 path_expr
             } else {
                 let fields = fields
@@ -209,7 +209,7 @@ where
                 cx.expr_call(trait_span, path_expr, fields)
             }
         }
-        Named(ref fields) => {
+        Named(fields) => {
             // use the field's span to get nicer error messages.
             let fields = fields
                 .iter()
diff --git a/compiler/rustc_builtin_macros/src/deriving/default.rs b/compiler/rustc_builtin_macros/src/deriving/default.rs
index e88d2e409c6..eb66c4a69a6 100644
--- a/compiler/rustc_builtin_macros/src/deriving/default.rs
+++ b/compiler/rustc_builtin_macros/src/deriving/default.rs
@@ -62,15 +62,12 @@ fn default_struct_substructure(
     let default_call = |span| cx.expr_call_global(span, default_ident.clone(), Vec::new());
 
     let expr = match summary {
-        Unnamed(ref fields, is_tuple) => {
-            if !is_tuple {
-                cx.expr_ident(trait_span, substr.type_ident)
-            } else {
-                let exprs = fields.iter().map(|sp| default_call(*sp)).collect();
-                cx.expr_call_ident(trait_span, substr.type_ident, exprs)
-            }
+        Unnamed(_, false) => cx.expr_ident(trait_span, substr.type_ident),
+        Unnamed(fields, true) => {
+            let exprs = fields.iter().map(|sp| default_call(*sp)).collect();
+            cx.expr_call_ident(trait_span, substr.type_ident, exprs)
         }
-        Named(ref fields) => {
+        Named(fields) => {
             let default_fields = fields
                 .iter()
                 .map(|&(ident, span)| cx.field_imm(span, ident, default_call(span)))
diff --git a/compiler/rustc_builtin_macros/src/deriving/encodable.rs b/compiler/rustc_builtin_macros/src/deriving/encodable.rs
index 9a46ca81537..68bc0ff2ec0 100644
--- a/compiler/rustc_builtin_macros/src/deriving/encodable.rs
+++ b/compiler/rustc_builtin_macros/src/deriving/encodable.rs
@@ -164,8 +164,8 @@ fn encodable_substructure(
         ],
     ));
 
-    match *substr.fields {
-        Struct(_, ref fields) => {
+    match substr.fields {
+        Struct(_, fields) => {
             let fn_emit_struct_field_path =
                 cx.def_site_path(&[sym::rustc_serialize, sym::Encoder, sym::emit_struct_field]);
             let mut stmts = Vec::new();
@@ -224,7 +224,7 @@ fn encodable_substructure(
             BlockOrExpr::new_expr(expr)
         }
 
-        EnumMatching(idx, _, variant, ref fields) => {
+        EnumMatching(idx, _, variant, fields) => {
             // We're not generating an AST that the borrow checker is expecting,
             // so we need to generate a unique local variable to take the
             // mutable loan out on, otherwise we get conflicts which don't
@@ -274,7 +274,7 @@ fn encodable_substructure(
                 vec![
                     blkencoder,
                     name,
-                    cx.expr_usize(trait_span, idx),
+                    cx.expr_usize(trait_span, *idx),
                     cx.expr_usize(trait_span, fields.len()),
                     blk,
                 ],
diff --git a/compiler/rustc_builtin_macros/src/deriving/generic/mod.rs b/compiler/rustc_builtin_macros/src/deriving/generic/mod.rs
index 7fcaf0b436b..beac591bfc8 100644
--- a/compiler/rustc_builtin_macros/src/deriving/generic/mod.rs
+++ b/compiler/rustc_builtin_macros/src/deriving/generic/mod.rs
@@ -369,15 +369,14 @@ fn find_type_parameters(
 
     impl<'a, 'b> visit::Visitor<'a> for Visitor<'a, 'b> {
         fn visit_ty(&mut self, ty: &'a ast::Ty) {
-            if let ast::TyKind::Path(_, ref path) = ty.kind {
-                if let Some(segment) = path.segments.first() {
-                    if self.ty_param_names.contains(&segment.ident.name) {
-                        self.type_params.push(TypeParameter {
-                            bound_generic_params: self.bound_generic_params_stack.clone(),
-                            ty: P(ty.clone()),
-                        });
-                    }
-                }
+            if let ast::TyKind::Path(_, path) = &ty.kind
+                && let Some(segment) = path.segments.first()
+                && self.ty_param_names.contains(&segment.ident.name)
+            {
+                self.type_params.push(TypeParameter {
+                    bound_generic_params: self.bound_generic_params_stack.clone(),
+                    ty: P(ty.clone()),
+                });
             }
 
             visit::walk_ty(self, ty)
@@ -428,8 +427,8 @@ impl<'a> TraitDef<'a> {
         push: &mut dyn FnMut(Annotatable),
         from_scratch: bool,
     ) {
-        match *item {
-            Annotatable::Item(ref item) => {
+        match item {
+            Annotatable::Item(item) => {
                 let is_packed = item.attrs.iter().any(|attr| {
                     for r in attr::find_repr_attrs(&cx.sess, attr) {
                         if let attr::ReprPacked(_) = r {
@@ -438,10 +437,10 @@ impl<'a> TraitDef<'a> {
                     }
                     false
                 });
-                let has_no_type_params = match item.kind {
-                    ast::ItemKind::Struct(_, ref generics)
-                    | ast::ItemKind::Enum(_, ref generics)
-                    | ast::ItemKind::Union(_, ref generics) => !generics
+                let has_no_type_params = match &item.kind {
+                    ast::ItemKind::Struct(_, generics)
+                    | ast::ItemKind::Enum(_, generics)
+                    | ast::ItemKind::Union(_, generics) => !generics
                         .params
                         .iter()
                         .any(|param| matches!(param.kind, ast::GenericParamKind::Type { .. })),
@@ -451,8 +450,8 @@ impl<'a> TraitDef<'a> {
                 let copy_fields =
                     is_packed && has_no_type_params && cx.resolver.has_derive_copy(container_id);
 
-                let newitem = match item.kind {
-                    ast::ItemKind::Struct(ref struct_def, ref generics) => self.expand_struct_def(
+                let newitem = match &item.kind {
+                    ast::ItemKind::Struct(struct_def, generics) => self.expand_struct_def(
                         cx,
                         &struct_def,
                         item.ident,
@@ -460,7 +459,7 @@ impl<'a> TraitDef<'a> {
                         from_scratch,
                         copy_fields,
                     ),
-                    ast::ItemKind::Enum(ref enum_def, ref generics) => {
+                    ast::ItemKind::Enum(enum_def, generics) => {
                         // We ignore `is_packed` here, because `repr(packed)`
                         // enums cause an error later on.
                         //
@@ -468,7 +467,7 @@ impl<'a> TraitDef<'a> {
                         // downstream in blatantly illegal code, so it is fine.
                         self.expand_enum_def(cx, enum_def, item.ident, generics, from_scratch)
                     }
-                    ast::ItemKind::Union(ref struct_def, ref generics) => {
+                    ast::ItemKind::Union(struct_def, generics) => {
                         if self.supports_unions {
                             self.expand_struct_def(
                                 cx,
@@ -663,12 +662,11 @@ impl<'a> TraitDef<'a> {
 
                     for field_ty_param in field_ty_params {
                         // if we have already handled this type, skip it
-                        if let ast::TyKind::Path(_, ref p) = field_ty_param.ty.kind {
-                            if p.segments.len() == 1
-                                && ty_param_names.contains(&p.segments[0].ident.name)
-                            {
-                                continue;
-                            };
+                        if let ast::TyKind::Path(_, p) = &field_ty_param.ty.kind
+                            && let [sole_segment] = &*p.segments
+                            && ty_param_names.contains(&sole_segment.ident.name)
+                        {
+                            continue;
                         }
                         let mut bounds: Vec<_> = self
                             .additional_bounds
diff --git a/compiler/rustc_builtin_macros/src/deriving/generic/ty.rs b/compiler/rustc_builtin_macros/src/deriving/generic/ty.rs
index 36e2e293086..eaa4881906a 100644
--- a/compiler/rustc_builtin_macros/src/deriving/generic/ty.rs
+++ b/compiler/rustc_builtin_macros/src/deriving/generic/ty.rs
@@ -115,7 +115,7 @@ impl Ty {
         self_ty: Ident,
         generics: &Generics,
     ) -> ast::Path {
-        match *self {
+        match self {
             Self_ => {
                 let params: Vec<_> = generics
                     .params
@@ -135,7 +135,7 @@ impl Ty {
 
                 cx.path_all(span, false, vec![self_ty], params)
             }
-            Path(ref p) => p.to_path(cx, span, self_ty, generics),
+            Path(p) => p.to_path(cx, span, self_ty, generics),
             Ref(..) => cx.span_bug(span, "ref in a path in generic `derive`"),
             Unit => cx.span_bug(span, "unit in a path in generic `derive`"),
         }
@@ -180,10 +180,7 @@ impl Bounds {
         let params = self
             .bounds
             .iter()
-            .map(|t| {
-                let (name, ref bounds) = *t;
-                mk_ty_param(cx, span, name, &bounds, self_ty, self_generics)
-            })
+            .map(|&(name, ref bounds)| mk_ty_param(cx, span, name, &bounds, self_ty, self_generics))
             .collect();
 
         Generics {
diff --git a/compiler/rustc_builtin_macros/src/deriving/mod.rs b/compiler/rustc_builtin_macros/src/deriving/mod.rs
index 13fdd4fa68c..de657e4e600 100644
--- a/compiler/rustc_builtin_macros/src/deriving/mod.rs
+++ b/compiler/rustc_builtin_macros/src/deriving/mod.rs
@@ -125,12 +125,12 @@ fn inject_impl_of_structural_trait(
     structural_path: generic::ty::Path,
     push: &mut dyn FnMut(Annotatable),
 ) {
-    let Annotatable::Item(ref item) = *item else {
+    let Annotatable::Item(item) = item else {
         unreachable!();
     };
 
-    let generics = match item.kind {
-        ItemKind::Struct(_, ref generics) | ItemKind::Enum(_, ref generics) => generics,
+    let generics = match &item.kind {
+        ItemKind::Struct(_, generics) | ItemKind::Enum(_, generics) => generics,
         // Do not inject `impl Structural for Union`. (`PartialEq` does not
         // support unions, so we will see error downstream.)
         ItemKind::Union(..) => return,
diff --git a/compiler/rustc_builtin_macros/src/env.rs b/compiler/rustc_builtin_macros/src/env.rs
index b8828fa671a..0b4e545f7a3 100644
--- a/compiler/rustc_builtin_macros/src/env.rs
+++ b/compiler/rustc_builtin_macros/src/env.rs
@@ -53,7 +53,7 @@ pub fn expand_env<'cx>(
     tts: TokenStream,
 ) -> Box<dyn base::MacResult + 'cx> {
     let mut exprs = match get_exprs_from_tts(cx, sp, tts) {
-        Some(ref exprs) if exprs.is_empty() => {
+        Some(exprs) if exprs.is_empty() => {
             cx.span_err(sp, "env! takes 1 or 2 arguments");
             return DummyResult::any(sp);
         }
diff --git a/compiler/rustc_builtin_macros/src/format_foreign.rs b/compiler/rustc_builtin_macros/src/format_foreign.rs
index ecd16736e7c..6f7fc3a95ba 100644
--- a/compiler/rustc_builtin_macros/src/format_foreign.rs
+++ b/compiler/rustc_builtin_macros/src/format_foreign.rs
@@ -13,23 +13,23 @@ pub(crate) mod printf {
 
     impl<'a> Substitution<'a> {
         pub fn as_str(&self) -> &str {
-            match *self {
-                Substitution::Format(ref fmt) => fmt.span,
+            match self {
+                Substitution::Format(fmt) => fmt.span,
                 Substitution::Escape(_) => "%%",
             }
         }
 
         pub fn position(&self) -> Option<InnerSpan> {
-            match *self {
-                Substitution::Format(ref fmt) => Some(fmt.position),
-                Substitution::Escape((start, end)) => Some(InnerSpan::new(start, end)),
+            match self {
+                Substitution::Format(fmt) => Some(fmt.position),
+                &Substitution::Escape((start, end)) => Some(InnerSpan::new(start, end)),
             }
         }
 
         pub fn set_position(&mut self, start: usize, end: usize) {
             match self {
-                Substitution::Format(ref mut fmt) => fmt.position = InnerSpan::new(start, end),
-                Substitution::Escape(ref mut pos) => *pos = (start, end),
+                Substitution::Format(fmt) => fmt.position = InnerSpan::new(start, end),
+                Substitution::Escape(pos) => *pos = (start, end),
             }
         }
 
@@ -38,8 +38,8 @@ pub(crate) mod printf {
         /// This ignores cases where the substitution does not have an exact equivalent, or where
         /// the substitution would be unnecessary.
         pub fn translate(&self) -> Result<String, Option<String>> {
-            match *self {
-                Substitution::Format(ref fmt) => fmt.translate(),
+            match self {
+                Substitution::Format(fmt) => fmt.translate(),
                 Substitution::Escape(_) => Err(None),
             }
         }
@@ -635,23 +635,17 @@ pub mod shell {
         }
 
         pub fn position(&self) -> Option<InnerSpan> {
-            match self {
-                Substitution::Ordinal(_, pos)
-                | Substitution::Name(_, pos)
-                | Substitution::Escape(pos) => Some(InnerSpan::new(pos.0, pos.1)),
-            }
+            let (Self::Ordinal(_, pos) | Self::Name(_, pos) | Self::Escape(pos)) = self;
+            Some(InnerSpan::new(pos.0, pos.1))
         }
 
         pub fn set_position(&mut self, start: usize, end: usize) {
-            match self {
-                Substitution::Ordinal(_, ref mut pos)
-                | Substitution::Name(_, ref mut pos)
-                | Substitution::Escape(ref mut pos) => *pos = (start, end),
-            }
+            let (Self::Ordinal(_, pos) | Self::Name(_, pos) | Self::Escape(pos)) = self;
+            *pos = (start, end);
         }
 
         pub fn translate(&self) -> Result<String, Option<String>> {
-            match *self {
+            match self {
                 Substitution::Ordinal(n, _) => Ok(format!("{{{}}}", n)),
                 Substitution::Name(n, _) => Ok(format!("{{{}}}", n)),
                 Substitution::Escape(_) => Err(None),
diff --git a/compiler/rustc_builtin_macros/src/global_allocator.rs b/compiler/rustc_builtin_macros/src/global_allocator.rs
index 0817aed037e..41531580c19 100644
--- a/compiler/rustc_builtin_macros/src/global_allocator.rs
+++ b/compiler/rustc_builtin_macros/src/global_allocator.rs
@@ -20,27 +20,23 @@ pub fn expand(
     check_builtin_macro_attribute(ecx, meta_item, sym::global_allocator);
 
     let orig_item = item.clone();
-    let not_static = || {
-        ecx.sess.parse_sess.span_diagnostic.span_err(item.span(), "allocators must be statics");
-        vec![orig_item.clone()]
-    };
 
     // Allow using `#[global_allocator]` on an item statement
     // FIXME - if we get deref patterns, use them to reduce duplication here
-    let (item, is_stmt, ty_span) = match &item {
-        Annotatable::Item(item) => match item.kind {
-            ItemKind::Static(ref ty, ..) => (item, false, ecx.with_def_site_ctxt(ty.span)),
-            _ => return not_static(),
-        },
-        Annotatable::Stmt(stmt) => match &stmt.kind {
-            StmtKind::Item(item_) => match item_.kind {
-                ItemKind::Static(ref ty, ..) => (item_, true, ecx.with_def_site_ctxt(ty.span)),
-                _ => return not_static(),
-            },
-            _ => return not_static(),
-        },
-        _ => return not_static(),
-    };
+    let (item, is_stmt, ty_span) =
+        if let Annotatable::Item(item) = &item
+            && let ItemKind::Static(ty, ..) = &item.kind
+        {
+            (item, false, ecx.with_def_site_ctxt(ty.span))
+        } else if let Annotatable::Stmt(stmt) = &item
+            && let StmtKind::Item(item) = &stmt.kind
+            && let ItemKind::Static(ty, ..) = &item.kind
+        {
+            (item, true, ecx.with_def_site_ctxt(ty.span))
+        } else {
+            ecx.sess.parse_sess.span_diagnostic.span_err(item.span(), "allocators must be statics");
+            return vec![orig_item.clone()]
+        };
 
     // Generate a bunch of new items using the AllocFnFactory
     let span = ecx.with_def_site_ctxt(item.span);
diff --git a/compiler/rustc_builtin_macros/src/test.rs b/compiler/rustc_builtin_macros/src/test.rs
index 3bcb60478ef..f5f02fc772a 100644
--- a/compiler/rustc_builtin_macros/src/test.rs
+++ b/compiler/rustc_builtin_macros/src/test.rs
@@ -466,61 +466,67 @@ fn test_type(cx: &ExtCtxt<'_>) -> TestType {
 fn has_test_signature(cx: &ExtCtxt<'_>, i: &ast::Item) -> bool {
     let has_should_panic_attr = cx.sess.contains_name(&i.attrs, sym::should_panic);
     let sd = &cx.sess.parse_sess.span_diagnostic;
-    if let ast::ItemKind::Fn(box ast::Fn { ref sig, ref generics, .. }) = i.kind {
-        if let ast::Unsafe::Yes(span) = sig.header.unsafety {
-            sd.struct_span_err(i.span, "unsafe functions cannot be used for tests")
-                .span_label(span, "`unsafe` because of this")
-                .emit();
-            return false;
-        }
-        if let ast::Async::Yes { span, .. } = sig.header.asyncness {
-            sd.struct_span_err(i.span, "async functions cannot be used for tests")
-                .span_label(span, "`async` because of this")
-                .emit();
-            return false;
-        }
-
-        // If the termination trait is active, the compiler will check that the output
-        // type implements the `Termination` trait as `libtest` enforces that.
-        let has_output = match sig.decl.output {
-            ast::FnRetTy::Default(..) => false,
-            ast::FnRetTy::Ty(ref t) if t.kind.is_unit() => false,
-            _ => true,
-        };
-
-        if !sig.decl.inputs.is_empty() {
-            sd.span_err(i.span, "functions used as tests can not have any arguments");
-            return false;
-        }
+    match &i.kind {
+        ast::ItemKind::Fn(box ast::Fn { sig, generics, .. }) => {
+            if let ast::Unsafe::Yes(span) = sig.header.unsafety {
+                sd.struct_span_err(i.span, "unsafe functions cannot be used for tests")
+                    .span_label(span, "`unsafe` because of this")
+                    .emit();
+                return false;
+            }
+            if let ast::Async::Yes { span, .. } = sig.header.asyncness {
+                sd.struct_span_err(i.span, "async functions cannot be used for tests")
+                    .span_label(span, "`async` because of this")
+                    .emit();
+                return false;
+            }
 
-        match (has_output, has_should_panic_attr) {
-            (true, true) => {
-                sd.span_err(i.span, "functions using `#[should_panic]` must return `()`");
-                false
+            // If the termination trait is active, the compiler will check that the output
+            // type implements the `Termination` trait as `libtest` enforces that.
+            let has_output = match &sig.decl.output {
+                ast::FnRetTy::Default(..) => false,
+                ast::FnRetTy::Ty(t) if t.kind.is_unit() => false,
+                _ => true,
+            };
+
+            if !sig.decl.inputs.is_empty() {
+                sd.span_err(i.span, "functions used as tests can not have any arguments");
+                return false;
             }
-            (true, false) => {
-                if !generics.params.is_empty() {
-                    sd.span_err(i.span, "functions used as tests must have signature fn() -> ()");
+
+            match (has_output, has_should_panic_attr) {
+                (true, true) => {
+                    sd.span_err(i.span, "functions using `#[should_panic]` must return `()`");
                     false
-                } else {
-                    true
                 }
+                (true, false) => {
+                    if !generics.params.is_empty() {
+                        sd.span_err(
+                            i.span,
+                            "functions used as tests must have signature fn() -> ()",
+                        );
+                        false
+                    } else {
+                        true
+                    }
+                }
+                (false, _) => true,
             }
-            (false, _) => true,
         }
-    } else {
-        // should be unreachable because `is_test_fn_item` should catch all non-fn items
-        false
+        _ => {
+            // should be unreachable because `is_test_fn_item` should catch all non-fn items
+            debug_assert!(false);
+            false
+        }
     }
 }
 
 fn has_bench_signature(cx: &ExtCtxt<'_>, i: &ast::Item) -> bool {
-    let has_sig = if let ast::ItemKind::Fn(box ast::Fn { ref sig, .. }) = i.kind {
+    let has_sig = match &i.kind {
         // N.B., inadequate check, but we're running
         // well before resolve, can't get too deep.
-        sig.decl.inputs.len() == 1
-    } else {
-        false
+        ast::ItemKind::Fn(box ast::Fn { sig, .. }) => sig.decl.inputs.len() == 1,
+        _ => false,
     };
 
     if !has_sig {
diff --git a/compiler/rustc_builtin_macros/src/test_harness.rs b/compiler/rustc_builtin_macros/src/test_harness.rs
index b5bce9278a9..ad887108091 100644
--- a/compiler/rustc_builtin_macros/src/test_harness.rs
+++ b/compiler/rustc_builtin_macros/src/test_harness.rs
@@ -131,8 +131,9 @@ impl<'a> MutVisitor for TestHarnessGenerator<'a> {
 
         // We don't want to recurse into anything other than mods, since
         // mods or tests inside of functions will break things
-        if let ast::ItemKind::Mod(_, ModKind::Loaded(.., ref spans)) = item.kind {
-            let ast::ModSpans { inner_span: span, inject_use_span: _ } = *spans;
+        if let ast::ItemKind::Mod(_, ModKind::Loaded(.., ast::ModSpans { inner_span: span, .. })) =
+            item.kind
+        {
             let prev_tests = mem::take(&mut self.tests);
             noop_visit_item_kind(&mut item.kind, self);
             self.add_test_cases(item.id, span, prev_tests);