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-rw-r--r--compiler/rustc_lint/src/builtin.rs4
-rw-r--r--compiler/rustc_lint/src/context.rs23
-rw-r--r--compiler/rustc_lint/src/dangling.rs152
-rw-r--r--compiler/rustc_lint/src/default_could_be_derived.rs6
-rw-r--r--compiler/rustc_lint/src/early.rs3
-rw-r--r--compiler/rustc_lint/src/foreign_modules.rs3
-rw-r--r--compiler/rustc_lint/src/lifetime_syntax.rs9
-rw-r--r--compiler/rustc_lint/src/lints.rs79
-rw-r--r--compiler/rustc_lint/src/map_unit_fn.rs103
-rw-r--r--compiler/rustc_lint/src/nonstandard_style.rs4
-rw-r--r--compiler/rustc_lint/src/pass_by_value.rs4
-rw-r--r--compiler/rustc_lint/src/types/literal.rs8
-rw-r--r--compiler/rustc_lint/src/unused.rs8
13 files changed, 273 insertions, 133 deletions
diff --git a/compiler/rustc_lint/src/builtin.rs b/compiler/rustc_lint/src/builtin.rs
index 152971c4ed6..c893b723375 100644
--- a/compiler/rustc_lint/src/builtin.rs
+++ b/compiler/rustc_lint/src/builtin.rs
@@ -21,14 +21,14 @@ use rustc_ast::tokenstream::{TokenStream, TokenTree};
 use rustc_ast::visit::{FnCtxt, FnKind};
 use rustc_ast::{self as ast, *};
 use rustc_ast_pretty::pprust::expr_to_string;
-use rustc_attr_data_structures::{AttributeKind, find_attr};
 use rustc_errors::{Applicability, LintDiagnostic};
 use rustc_feature::GateIssue;
 use rustc_hir as hir;
+use rustc_hir::attrs::AttributeKind;
 use rustc_hir::def::{DefKind, Res};
 use rustc_hir::def_id::{CRATE_DEF_ID, DefId, LocalDefId};
 use rustc_hir::intravisit::FnKind as HirFnKind;
-use rustc_hir::{Body, FnDecl, PatKind, PredicateOrigin};
+use rustc_hir::{Body, FnDecl, PatKind, PredicateOrigin, find_attr};
 use rustc_middle::bug;
 use rustc_middle::lint::LevelAndSource;
 use rustc_middle::ty::layout::LayoutOf;
diff --git a/compiler/rustc_lint/src/context.rs b/compiler/rustc_lint/src/context.rs
index b694d3dd49b..11181d10af5 100644
--- a/compiler/rustc_lint/src/context.rs
+++ b/compiler/rustc_lint/src/context.rs
@@ -756,22 +756,22 @@ impl<'tcx> LateContext<'tcx> {
             }
 
             fn print_region(&mut self, _region: ty::Region<'_>) -> Result<(), PrintError> {
-                Ok(())
+                unreachable!(); // because `path_generic_args` ignores the `GenericArgs`
             }
 
             fn print_type(&mut self, _ty: Ty<'tcx>) -> Result<(), PrintError> {
-                Ok(())
+                unreachable!(); // because `path_generic_args` ignores the `GenericArgs`
             }
 
             fn print_dyn_existential(
                 &mut self,
                 _predicates: &'tcx ty::List<ty::PolyExistentialPredicate<'tcx>>,
             ) -> Result<(), PrintError> {
-                Ok(())
+                unreachable!(); // because `path_generic_args` ignores the `GenericArgs`
             }
 
             fn print_const(&mut self, _ct: ty::Const<'tcx>) -> Result<(), PrintError> {
-                Ok(())
+                unreachable!(); // because `path_generic_args` ignores the `GenericArgs`
             }
 
             fn path_crate(&mut self, cnum: CrateNum) -> Result<(), PrintError> {
@@ -784,10 +784,10 @@ impl<'tcx> LateContext<'tcx> {
                 self_ty: Ty<'tcx>,
                 trait_ref: Option<ty::TraitRef<'tcx>>,
             ) -> Result<(), PrintError> {
-                if trait_ref.is_none() {
-                    if let ty::Adt(def, args) = self_ty.kind() {
-                        return self.print_def_path(def.did(), args);
-                    }
+                if trait_ref.is_none()
+                    && let ty::Adt(def, args) = self_ty.kind()
+                {
+                    return self.print_def_path(def.did(), args);
                 }
 
                 // This shouldn't ever be needed, but just in case:
@@ -803,7 +803,6 @@ impl<'tcx> LateContext<'tcx> {
             fn path_append_impl(
                 &mut self,
                 print_prefix: impl FnOnce(&mut Self) -> Result<(), PrintError>,
-                _disambiguated_data: &DisambiguatedDefPathData,
                 self_ty: Ty<'tcx>,
                 trait_ref: Option<ty::TraitRef<'tcx>>,
             ) -> Result<(), PrintError> {
@@ -854,9 +853,9 @@ impl<'tcx> LateContext<'tcx> {
             }
         }
 
-        let mut printer = AbsolutePathPrinter { tcx: self.tcx, path: vec![] };
-        printer.print_def_path(def_id, &[]).unwrap();
-        printer.path
+        let mut p = AbsolutePathPrinter { tcx: self.tcx, path: vec![] };
+        p.print_def_path(def_id, &[]).unwrap();
+        p.path
     }
 
     /// Returns the associated type `name` for `self_ty` as an implementation of `trait_id`.
diff --git a/compiler/rustc_lint/src/dangling.rs b/compiler/rustc_lint/src/dangling.rs
index c737919db9c..af4457f4314 100644
--- a/compiler/rustc_lint/src/dangling.rs
+++ b/compiler/rustc_lint/src/dangling.rs
@@ -1,13 +1,14 @@
 use rustc_ast::visit::{visit_opt, walk_list};
-use rustc_attr_data_structures::{AttributeKind, find_attr};
+use rustc_hir::attrs::AttributeKind;
+use rustc_hir::def::Res;
 use rustc_hir::def_id::LocalDefId;
 use rustc_hir::intravisit::{FnKind, Visitor, walk_expr};
-use rustc_hir::{Block, Body, Expr, ExprKind, FnDecl, LangItem};
-use rustc_middle::ty::{Ty, TyCtxt};
+use rustc_hir::{Block, Body, Expr, ExprKind, FnDecl, FnRetTy, LangItem, TyKind, find_attr};
+use rustc_middle::ty::{self, Ty, TyCtxt};
 use rustc_session::{declare_lint, impl_lint_pass};
 use rustc_span::{Span, sym};
 
-use crate::lints::DanglingPointersFromTemporaries;
+use crate::lints::{DanglingPointersFromLocals, DanglingPointersFromTemporaries};
 use crate::{LateContext, LateLintPass};
 
 declare_lint! {
@@ -42,6 +43,36 @@ declare_lint! {
     "detects getting a pointer from a temporary"
 }
 
+declare_lint! {
+    /// The `dangling_pointers_from_locals` lint detects getting a pointer to data
+    /// of a local that will be dropped at the end of the function.
+    ///
+    /// ### Example
+    ///
+    /// ```rust
+    /// fn f() -> *const u8 {
+    ///     let x = 0;
+    ///     &x // returns a dangling ptr to `x`
+    /// }
+    /// ```
+    ///
+    /// {{produces}}
+    ///
+    /// ### Explanation
+    ///
+    /// Returning a pointer from a local value will not prolong its lifetime,
+    /// which means that the value can be dropped and the allocation freed
+    /// while the pointer still exists, making the pointer dangling.
+    /// This is not an error (as far as the type system is concerned)
+    /// but probably is not what the user intended either.
+    ///
+    /// If you need stronger guarantees, consider using references instead,
+    /// as they are statically verified by the borrow-checker to never dangle.
+    pub DANGLING_POINTERS_FROM_LOCALS,
+    Warn,
+    "detects returning a pointer from a local variable"
+}
+
 /// FIXME: false negatives (i.e. the lint is not emitted when it should be)
 /// 1. Ways to get a temporary that are not recognized:
 ///    - `owning_temporary.field`
@@ -53,20 +84,123 @@ declare_lint! {
 #[derive(Clone, Copy, Default)]
 pub(crate) struct DanglingPointers;
 
-impl_lint_pass!(DanglingPointers => [DANGLING_POINTERS_FROM_TEMPORARIES]);
+impl_lint_pass!(DanglingPointers => [DANGLING_POINTERS_FROM_TEMPORARIES, DANGLING_POINTERS_FROM_LOCALS]);
 
 // This skips over const blocks, but they cannot use or return a dangling pointer anyways.
 impl<'tcx> LateLintPass<'tcx> for DanglingPointers {
     fn check_fn(
         &mut self,
         cx: &LateContext<'tcx>,
-        _: FnKind<'tcx>,
-        _: &'tcx FnDecl<'tcx>,
+        fn_kind: FnKind<'tcx>,
+        fn_decl: &'tcx FnDecl<'tcx>,
         body: &'tcx Body<'tcx>,
         _: Span,
-        _: LocalDefId,
+        def_id: LocalDefId,
     ) {
-        DanglingPointerSearcher { cx, inside_call_args: false }.visit_body(body)
+        DanglingPointerSearcher { cx, inside_call_args: false }.visit_body(body);
+
+        if let FnRetTy::Return(ret_ty) = &fn_decl.output
+            && let TyKind::Ptr(_) = ret_ty.kind
+        {
+            // get the return type of the function or closure
+            let ty = match cx.tcx.type_of(def_id).instantiate_identity().kind() {
+                ty::FnDef(..) => cx.tcx.fn_sig(def_id).instantiate_identity(),
+                ty::Closure(_, args) => args.as_closure().sig(),
+                _ => return,
+            };
+            let ty = ty.output();
+
+            // this type is only used for layout computation and pretty-printing, neither of them rely on regions
+            let ty = cx.tcx.instantiate_bound_regions_with_erased(ty);
+
+            // verify that we have a pointer type
+            let inner_ty = match ty.kind() {
+                ty::RawPtr(inner_ty, _) => *inner_ty,
+                _ => return,
+            };
+
+            if cx
+                .tcx
+                .layout_of(cx.typing_env().as_query_input(inner_ty))
+                .is_ok_and(|layout| !layout.is_1zst())
+            {
+                let dcx = &DanglingPointerLocalContext {
+                    body: def_id,
+                    fn_ret: ty,
+                    fn_ret_span: ret_ty.span,
+                    fn_ret_inner: inner_ty,
+                    fn_kind: match fn_kind {
+                        FnKind::ItemFn(..) => "function",
+                        FnKind::Method(..) => "method",
+                        FnKind::Closure => "closure",
+                    },
+                };
+
+                // look for `return`s
+                DanglingPointerReturnSearcher { cx, dcx }.visit_body(body);
+
+                // analyze implicit return expression
+                if let ExprKind::Block(block, None) = &body.value.kind
+                    && let innermost_block = block.innermost_block()
+                    && let Some(expr) = innermost_block.expr
+                {
+                    lint_addr_of_local(cx, dcx, expr);
+                }
+            }
+        }
+    }
+}
+
+struct DanglingPointerLocalContext<'tcx> {
+    body: LocalDefId,
+    fn_ret: Ty<'tcx>,
+    fn_ret_span: Span,
+    fn_ret_inner: Ty<'tcx>,
+    fn_kind: &'static str,
+}
+
+struct DanglingPointerReturnSearcher<'lcx, 'tcx> {
+    cx: &'lcx LateContext<'tcx>,
+    dcx: &'lcx DanglingPointerLocalContext<'tcx>,
+}
+
+impl<'tcx> Visitor<'tcx> for DanglingPointerReturnSearcher<'_, 'tcx> {
+    fn visit_expr(&mut self, expr: &'tcx Expr<'tcx>) -> Self::Result {
+        if let ExprKind::Ret(Some(expr)) = expr.kind {
+            lint_addr_of_local(self.cx, self.dcx, expr);
+        }
+        walk_expr(self, expr)
+    }
+}
+
+/// Look for `&<path_to_local_in_same_body>` pattern and emit lint for it
+fn lint_addr_of_local<'a>(
+    cx: &LateContext<'a>,
+    dcx: &DanglingPointerLocalContext<'a>,
+    expr: &'a Expr<'a>,
+) {
+    // peel casts as they do not interest us here, we want the inner expression.
+    let (inner, _) = super::utils::peel_casts(cx, expr);
+
+    if let ExprKind::AddrOf(_, _, inner_of) = inner.kind
+        && let ExprKind::Path(ref qpath) = inner_of.peel_blocks().kind
+        && let Res::Local(from) = cx.qpath_res(qpath, inner_of.hir_id)
+        && cx.tcx.hir_enclosing_body_owner(from) == dcx.body
+    {
+        cx.tcx.emit_node_span_lint(
+            DANGLING_POINTERS_FROM_LOCALS,
+            expr.hir_id,
+            expr.span,
+            DanglingPointersFromLocals {
+                ret_ty: dcx.fn_ret,
+                ret_ty_span: dcx.fn_ret_span,
+                fn_kind: dcx.fn_kind,
+                local_var: cx.tcx.hir_span(from),
+                local_var_name: cx.tcx.hir_ident(from),
+                local_var_ty: dcx.fn_ret_inner,
+                created_at: (expr.hir_id != inner.hir_id).then_some(inner.span),
+            },
+        );
     }
 }
 
diff --git a/compiler/rustc_lint/src/default_could_be_derived.rs b/compiler/rustc_lint/src/default_could_be_derived.rs
index b5fc083a095..1d92cfbc039 100644
--- a/compiler/rustc_lint/src/default_could_be_derived.rs
+++ b/compiler/rustc_lint/src/default_could_be_derived.rs
@@ -1,7 +1,8 @@
-use rustc_attr_data_structures::{AttributeKind, find_attr};
 use rustc_data_structures::fx::FxHashMap;
 use rustc_errors::{Applicability, Diag};
 use rustc_hir as hir;
+use rustc_hir::attrs::AttributeKind;
+use rustc_hir::find_attr;
 use rustc_middle::ty;
 use rustc_middle::ty::TyCtxt;
 use rustc_session::{declare_lint, impl_lint_pass};
@@ -61,8 +62,7 @@ impl<'tcx> LateLintPass<'tcx> for DefaultCouldBeDerived {
         // Look for manual implementations of `Default`.
         let Some(default_def_id) = cx.tcx.get_diagnostic_item(sym::Default) else { return };
         let hir::ImplItemKind::Fn(_sig, body_id) = impl_item.kind else { return };
-        let assoc = cx.tcx.associated_item(impl_item.owner_id);
-        let parent = assoc.container_id(cx.tcx);
+        let parent = cx.tcx.parent(impl_item.owner_id.to_def_id());
         if find_attr!(cx.tcx.get_all_attrs(parent), AttributeKind::AutomaticallyDerived(..)) {
             // We don't care about what `#[derive(Default)]` produces in this lint.
             return;
diff --git a/compiler/rustc_lint/src/early.rs b/compiler/rustc_lint/src/early.rs
index 48e3bbb79fa..58205087def 100644
--- a/compiler/rustc_lint/src/early.rs
+++ b/compiler/rustc_lint/src/early.rs
@@ -4,7 +4,6 @@
 //! resolution, just before AST lowering. These lints are for purely
 //! syntactical lints.
 
-use rustc_ast::ptr::P;
 use rustc_ast::visit::{self as ast_visit, Visitor, walk_list};
 use rustc_ast::{self as ast, HasAttrs};
 use rustc_data_structures::stack::ensure_sufficient_stack;
@@ -297,7 +296,7 @@ impl<'a> EarlyCheckNode<'a> for (&'a ast::Crate, &'a [ast::Attribute]) {
     }
 }
 
-impl<'a> EarlyCheckNode<'a> for (ast::NodeId, &'a [ast::Attribute], &'a [P<ast::Item>]) {
+impl<'a> EarlyCheckNode<'a> for (ast::NodeId, &'a [ast::Attribute], &'a [Box<ast::Item>]) {
     fn id(self) -> ast::NodeId {
         self.0
     }
diff --git a/compiler/rustc_lint/src/foreign_modules.rs b/compiler/rustc_lint/src/foreign_modules.rs
index d6c402d481f..759e6c927b8 100644
--- a/compiler/rustc_lint/src/foreign_modules.rs
+++ b/compiler/rustc_lint/src/foreign_modules.rs
@@ -1,9 +1,10 @@
 use rustc_abi::FIRST_VARIANT;
-use rustc_attr_data_structures::{AttributeKind, find_attr};
 use rustc_data_structures::stack::ensure_sufficient_stack;
 use rustc_data_structures::unord::{UnordMap, UnordSet};
 use rustc_hir as hir;
+use rustc_hir::attrs::AttributeKind;
 use rustc_hir::def::DefKind;
+use rustc_hir::find_attr;
 use rustc_middle::query::Providers;
 use rustc_middle::ty::{self, AdtDef, Instance, Ty, TyCtxt};
 use rustc_session::declare_lint;
diff --git a/compiler/rustc_lint/src/lifetime_syntax.rs b/compiler/rustc_lint/src/lifetime_syntax.rs
index 2a5a34cdc6e..464f4fc34b9 100644
--- a/compiler/rustc_lint/src/lifetime_syntax.rs
+++ b/compiler/rustc_lint/src/lifetime_syntax.rs
@@ -434,7 +434,7 @@ fn emit_mismatch_diagnostic<'tcx>(
         lints::MismatchedLifetimeSyntaxesSuggestion::Mixed {
             implicit_suggestions,
             explicit_anonymous_suggestions,
-            tool_only: false,
+            optional_alternative: false,
         }
     });
 
@@ -455,7 +455,10 @@ fn emit_mismatch_diagnostic<'tcx>(
     let implicit_suggestion = should_suggest_implicit.then(|| {
         let suggestions = make_implicit_suggestions(&suggest_change_to_implicit);
 
-        lints::MismatchedLifetimeSyntaxesSuggestion::Implicit { suggestions, tool_only: false }
+        lints::MismatchedLifetimeSyntaxesSuggestion::Implicit {
+            suggestions,
+            optional_alternative: false,
+        }
     });
 
     tracing::debug!(
@@ -508,7 +511,7 @@ fn build_mismatch_suggestion(
     lints::MismatchedLifetimeSyntaxesSuggestion::Explicit {
         lifetime_name,
         suggestions,
-        tool_only: false,
+        optional_alternative: false,
     }
 }
 
diff --git a/compiler/rustc_lint/src/lints.rs b/compiler/rustc_lint/src/lints.rs
index fd8d0f832aa..73e69a1791a 100644
--- a/compiler/rustc_lint/src/lints.rs
+++ b/compiler/rustc_lint/src/lints.rs
@@ -902,9 +902,8 @@ pub(crate) struct MappingToUnit {
     pub argument_label: Span,
     #[label(lint_map_label)]
     pub map_label: Span,
-    #[suggestion(style = "verbose", code = "{replace}", applicability = "maybe-incorrect")]
+    #[suggestion(style = "verbose", code = "for_each", applicability = "maybe-incorrect")]
     pub suggestion: Span,
-    pub replace: String,
 }
 
 // internal.rs
@@ -1188,6 +1187,22 @@ pub(crate) struct DanglingPointersFromTemporaries<'tcx> {
     pub temporary_span: Span,
 }
 
+#[derive(LintDiagnostic)]
+#[diag(lint_dangling_pointers_from_locals)]
+#[note]
+pub(crate) struct DanglingPointersFromLocals<'tcx> {
+    pub ret_ty: Ty<'tcx>,
+    #[label(lint_ret_ty)]
+    pub ret_ty_span: Span,
+    pub fn_kind: &'static str,
+    #[label(lint_local_var)]
+    pub local_var: Span,
+    pub local_var_name: Ident,
+    pub local_var_ty: Ty<'tcx>,
+    #[label(lint_created_at)]
+    pub created_at: Option<Span>,
+}
+
 // multiple_supertrait_upcastable.rs
 #[derive(LintDiagnostic)]
 #[diag(lint_multiple_supertrait_upcastable)]
@@ -3276,7 +3291,7 @@ impl<'a, G: EmissionGuarantee> LintDiagnostic<'a, G> for MismatchedLifetimeSynta
             diag.subdiagnostic(s);
 
             for mut s in suggestions {
-                s.make_tool_only();
+                s.make_optional_alternative();
                 diag.subdiagnostic(s);
             }
         }
@@ -3287,33 +3302,33 @@ impl<'a, G: EmissionGuarantee> LintDiagnostic<'a, G> for MismatchedLifetimeSynta
 pub(crate) enum MismatchedLifetimeSyntaxesSuggestion {
     Implicit {
         suggestions: Vec<Span>,
-        tool_only: bool,
+        optional_alternative: bool,
     },
 
     Mixed {
         implicit_suggestions: Vec<Span>,
         explicit_anonymous_suggestions: Vec<(Span, String)>,
-        tool_only: bool,
+        optional_alternative: bool,
     },
 
     Explicit {
         lifetime_name: String,
         suggestions: Vec<(Span, String)>,
-        tool_only: bool,
+        optional_alternative: bool,
     },
 }
 
 impl MismatchedLifetimeSyntaxesSuggestion {
-    fn make_tool_only(&mut self) {
+    fn make_optional_alternative(&mut self) {
         use MismatchedLifetimeSyntaxesSuggestion::*;
 
-        let tool_only = match self {
-            Implicit { tool_only, .. } | Mixed { tool_only, .. } | Explicit { tool_only, .. } => {
-                tool_only
-            }
+        let optional_alternative = match self {
+            Implicit { optional_alternative, .. }
+            | Mixed { optional_alternative, .. }
+            | Explicit { optional_alternative, .. } => optional_alternative,
         };
 
-        *tool_only = true;
+        *optional_alternative = true;
     }
 }
 
@@ -3321,22 +3336,40 @@ impl Subdiagnostic for MismatchedLifetimeSyntaxesSuggestion {
     fn add_to_diag<G: EmissionGuarantee>(self, diag: &mut Diag<'_, G>) {
         use MismatchedLifetimeSyntaxesSuggestion::*;
 
-        let style = |tool_only| {
-            if tool_only { SuggestionStyle::CompletelyHidden } else { SuggestionStyle::ShowAlways }
+        let style = |optional_alternative| {
+            if optional_alternative {
+                SuggestionStyle::CompletelyHidden
+            } else {
+                SuggestionStyle::ShowAlways
+            }
+        };
+
+        let applicability = |optional_alternative| {
+            // `cargo fix` can't handle more than one fix for the same issue,
+            // so hide alternative suggestions from it by marking them as maybe-incorrect
+            if optional_alternative {
+                Applicability::MaybeIncorrect
+            } else {
+                Applicability::MachineApplicable
+            }
         };
 
         match self {
-            Implicit { suggestions, tool_only } => {
+            Implicit { suggestions, optional_alternative } => {
                 let suggestions = suggestions.into_iter().map(|s| (s, String::new())).collect();
                 diag.multipart_suggestion_with_style(
                     fluent::lint_mismatched_lifetime_syntaxes_suggestion_implicit,
                     suggestions,
-                    Applicability::MaybeIncorrect,
-                    style(tool_only),
+                    applicability(optional_alternative),
+                    style(optional_alternative),
                 );
             }
 
-            Mixed { implicit_suggestions, explicit_anonymous_suggestions, tool_only } => {
+            Mixed {
+                implicit_suggestions,
+                explicit_anonymous_suggestions,
+                optional_alternative,
+            } => {
                 let message = if implicit_suggestions.is_empty() {
                     fluent::lint_mismatched_lifetime_syntaxes_suggestion_mixed_only_paths
                 } else {
@@ -3352,12 +3385,12 @@ impl Subdiagnostic for MismatchedLifetimeSyntaxesSuggestion {
                 diag.multipart_suggestion_with_style(
                     message,
                     suggestions,
-                    Applicability::MaybeIncorrect,
-                    style(tool_only),
+                    applicability(optional_alternative),
+                    style(optional_alternative),
                 );
             }
 
-            Explicit { lifetime_name, suggestions, tool_only } => {
+            Explicit { lifetime_name, suggestions, optional_alternative } => {
                 diag.arg("lifetime_name", lifetime_name);
                 let msg = diag.eagerly_translate(
                     fluent::lint_mismatched_lifetime_syntaxes_suggestion_explicit,
@@ -3366,8 +3399,8 @@ impl Subdiagnostic for MismatchedLifetimeSyntaxesSuggestion {
                 diag.multipart_suggestion_with_style(
                     msg,
                     suggestions,
-                    Applicability::MaybeIncorrect,
-                    style(tool_only),
+                    applicability(optional_alternative),
+                    style(optional_alternative),
                 );
             }
         }
diff --git a/compiler/rustc_lint/src/map_unit_fn.rs b/compiler/rustc_lint/src/map_unit_fn.rs
index 34210137bde..18a947dc1ee 100644
--- a/compiler/rustc_lint/src/map_unit_fn.rs
+++ b/compiler/rustc_lint/src/map_unit_fn.rs
@@ -1,6 +1,7 @@
-use rustc_hir::{Expr, ExprKind, HirId, Stmt, StmtKind};
-use rustc_middle::ty::{self, Ty};
+use rustc_hir::{Expr, ExprKind, Stmt, StmtKind};
+use rustc_middle::ty::{self};
 use rustc_session::{declare_lint, declare_lint_pass};
+use rustc_span::sym;
 
 use crate::lints::MappingToUnit;
 use crate::{LateContext, LateLintPass, LintContext};
@@ -39,58 +40,43 @@ declare_lint_pass!(MapUnitFn => [MAP_UNIT_FN]);
 
 impl<'tcx> LateLintPass<'tcx> for MapUnitFn {
     fn check_stmt(&mut self, cx: &LateContext<'tcx>, stmt: &Stmt<'_>) {
-        if stmt.span.from_expansion() {
+        let StmtKind::Semi(expr) = stmt.kind else {
             return;
-        }
-
-        if let StmtKind::Semi(expr) = stmt.kind
-            && let ExprKind::MethodCall(path, receiver, args, span) = expr.kind
+        };
+        let ExprKind::MethodCall(path, receiver, [arg], span) = expr.kind else {
+            return;
+        };
+        if path.ident.name != sym::map
+            || stmt.span.from_expansion()
+            || receiver.span.from_expansion()
+            || arg.span.from_expansion()
+            || !is_impl_slice(cx, receiver)
+            || !cx
+                .typeck_results()
+                .type_dependent_def_id(expr.hir_id)
+                .is_some_and(|id| cx.tcx.is_diagnostic_item(sym::IteratorMap, id))
         {
-            if path.ident.name.as_str() == "map" {
-                if receiver.span.from_expansion()
-                    || args.iter().any(|e| e.span.from_expansion())
-                    || !is_impl_slice(cx, receiver)
-                    || !is_diagnostic_name(cx, expr.hir_id, "IteratorMap")
-                {
-                    return;
-                }
-                let arg_ty = cx.typeck_results().expr_ty(&args[0]);
-                let default_span = args[0].span;
-                if let ty::FnDef(id, _) = arg_ty.kind() {
-                    let fn_ty = cx.tcx.fn_sig(id).skip_binder();
-                    let ret_ty = fn_ty.output().skip_binder();
-                    if is_unit_type(ret_ty) {
-                        cx.emit_span_lint(
-                            MAP_UNIT_FN,
-                            span,
-                            MappingToUnit {
-                                function_label: cx.tcx.span_of_impl(*id).unwrap_or(default_span),
-                                argument_label: args[0].span,
-                                map_label: span,
-                                suggestion: path.ident.span,
-                                replace: "for_each".to_string(),
-                            },
-                        )
-                    }
-                } else if let ty::Closure(id, subs) = arg_ty.kind() {
-                    let cl_ty = subs.as_closure().sig();
-                    let ret_ty = cl_ty.output().skip_binder();
-                    if is_unit_type(ret_ty) {
-                        cx.emit_span_lint(
-                            MAP_UNIT_FN,
-                            span,
-                            MappingToUnit {
-                                function_label: cx.tcx.span_of_impl(*id).unwrap_or(default_span),
-                                argument_label: args[0].span,
-                                map_label: span,
-                                suggestion: path.ident.span,
-                                replace: "for_each".to_string(),
-                            },
-                        )
-                    }
-                }
-            }
+            return;
         }
+        let (id, sig) = match *cx.typeck_results().expr_ty(arg).kind() {
+            ty::Closure(id, subs) => (id, subs.as_closure().sig()),
+            ty::FnDef(id, _) => (id, cx.tcx.fn_sig(id).skip_binder()),
+            _ => return,
+        };
+        let ret_ty = sig.output().skip_binder();
+        if !(ret_ty.is_unit() || ret_ty.is_never()) {
+            return;
+        }
+        cx.emit_span_lint(
+            MAP_UNIT_FN,
+            span,
+            MappingToUnit {
+                function_label: cx.tcx.span_of_impl(id).unwrap_or(arg.span),
+                argument_label: arg.span,
+                map_label: span,
+                suggestion: path.ident.span,
+            },
+        );
     }
 }
 
@@ -102,18 +88,3 @@ fn is_impl_slice(cx: &LateContext<'_>, expr: &Expr<'_>) -> bool {
     }
     false
 }
-
-fn is_unit_type(ty: Ty<'_>) -> bool {
-    ty.is_unit() || ty.is_never()
-}
-
-fn is_diagnostic_name(cx: &LateContext<'_>, id: HirId, name: &str) -> bool {
-    if let Some(def_id) = cx.typeck_results().type_dependent_def_id(id)
-        && let Some(item) = cx.tcx.get_diagnostic_name(def_id)
-    {
-        if item.as_str() == name {
-            return true;
-        }
-    }
-    false
-}
diff --git a/compiler/rustc_lint/src/nonstandard_style.rs b/compiler/rustc_lint/src/nonstandard_style.rs
index 76e374deef6..7e5f43ba77f 100644
--- a/compiler/rustc_lint/src/nonstandard_style.rs
+++ b/compiler/rustc_lint/src/nonstandard_style.rs
@@ -1,11 +1,11 @@
 use rustc_abi::ExternAbi;
-use rustc_attr_data_structures::{AttributeKind, ReprAttr, find_attr};
 use rustc_attr_parsing::AttributeParser;
 use rustc_errors::Applicability;
+use rustc_hir::attrs::{AttributeKind, ReprAttr};
 use rustc_hir::def::{DefKind, Res};
 use rustc_hir::def_id::DefId;
 use rustc_hir::intravisit::{FnKind, Visitor};
-use rustc_hir::{AttrArgs, AttrItem, Attribute, GenericParamKind, PatExprKind, PatKind};
+use rustc_hir::{AttrArgs, AttrItem, Attribute, GenericParamKind, PatExprKind, PatKind, find_attr};
 use rustc_middle::hir::nested_filter::All;
 use rustc_middle::ty;
 use rustc_session::config::CrateType;
diff --git a/compiler/rustc_lint/src/pass_by_value.rs b/compiler/rustc_lint/src/pass_by_value.rs
index a3cf3d568b1..4f65acd8001 100644
--- a/compiler/rustc_lint/src/pass_by_value.rs
+++ b/compiler/rustc_lint/src/pass_by_value.rs
@@ -1,6 +1,6 @@
-use rustc_attr_data_structures::{AttributeKind, find_attr};
+use rustc_hir::attrs::AttributeKind;
 use rustc_hir::def::Res;
-use rustc_hir::{self as hir, AmbigArg, GenericArg, PathSegment, QPath, TyKind};
+use rustc_hir::{self as hir, AmbigArg, GenericArg, PathSegment, QPath, TyKind, find_attr};
 use rustc_middle::ty;
 use rustc_session::{declare_lint_pass, declare_tool_lint};
 
diff --git a/compiler/rustc_lint/src/types/literal.rs b/compiler/rustc_lint/src/types/literal.rs
index 2bac58ba23d..1febbff4bbf 100644
--- a/compiler/rustc_lint/src/types/literal.rs
+++ b/compiler/rustc_lint/src/types/literal.rs
@@ -1,11 +1,11 @@
 use hir::{ExprKind, Node, is_range_literal};
 use rustc_abi::{Integer, Size};
-use rustc_hir::HirId;
+use rustc_hir::{HirId, attrs};
 use rustc_middle::ty::Ty;
 use rustc_middle::ty::layout::IntegerExt;
 use rustc_middle::{bug, ty};
 use rustc_span::Span;
-use {rustc_ast as ast, rustc_attr_data_structures as attrs, rustc_hir as hir};
+use {rustc_ast as ast, rustc_hir as hir};
 
 use crate::LateContext;
 use crate::context::LintContext;
@@ -272,7 +272,7 @@ fn lint_int_literal<'tcx>(
                 cx,
                 hir_id,
                 span,
-                attrs::IntType::SignedInt(ty::ast_int_ty(t)),
+                attrs::IntType::SignedInt(t),
                 Integer::from_int_ty(cx, t).size(),
                 repr_str,
                 v,
@@ -358,7 +358,7 @@ fn lint_uint_literal<'tcx>(
                 cx,
                 hir_id,
                 span,
-                attrs::IntType::UnsignedInt(ty::ast_uint_ty(t)),
+                attrs::IntType::UnsignedInt(t),
                 Integer::from_uint_ty(cx, t).size(),
                 repr_str,
                 lit_val,
diff --git a/compiler/rustc_lint/src/unused.rs b/compiler/rustc_lint/src/unused.rs
index 11df071f068..22d89d24612 100644
--- a/compiler/rustc_lint/src/unused.rs
+++ b/compiler/rustc_lint/src/unused.rs
@@ -2,12 +2,12 @@ use std::iter;
 
 use rustc_ast::util::{classify, parser};
 use rustc_ast::{self as ast, ExprKind, FnRetTy, HasAttrs as _, StmtKind};
-use rustc_attr_data_structures::{AttributeKind, find_attr};
 use rustc_data_structures::fx::FxHashMap;
 use rustc_errors::{MultiSpan, pluralize};
+use rustc_hir::attrs::AttributeKind;
 use rustc_hir::def::{DefKind, Res};
 use rustc_hir::def_id::DefId;
-use rustc_hir::{self as hir, LangItem};
+use rustc_hir::{self as hir, LangItem, find_attr};
 use rustc_infer::traits::util::elaborate;
 use rustc_middle::ty::{self, Ty, adjustment};
 use rustc_session::{declare_lint, declare_lint_pass, impl_lint_pass};
@@ -185,7 +185,7 @@ impl<'tcx> LateLintPass<'tcx> for UnusedResults {
         let mut op_warned = false;
 
         if let Some(must_use_op) = must_use_op {
-            let span = expr.span.find_oldest_ancestor_in_same_ctxt();
+            let span = expr.span.find_ancestor_not_from_macro().unwrap_or(expr.span);
             cx.emit_span_lint(
                 UNUSED_MUST_USE,
                 expr.span,
@@ -511,7 +511,7 @@ impl<'tcx> LateLintPass<'tcx> for UnusedResults {
                     );
                 }
                 MustUsePath::Def(span, def_id, reason) => {
-                    let span = span.find_oldest_ancestor_in_same_ctxt();
+                    let span = span.find_ancestor_not_from_macro().unwrap_or(*span);
                     cx.emit_span_lint(
                         UNUSED_MUST_USE,
                         span,