Skip use_self inside thread_local! of a impl Self block

Author: tesuji

clippy_lints/src/use_self.rs

@@ -15,7 +15,7 @@ use rustc_hir::{
 use rustc_lint::{LateContext, LateLintPass};
 use rustc_middle::ty::Ty as MiddleTy;
 use rustc_session::impl_lint_pass;
-use rustc_span::Span;
+use rustc_span::{sym, Span};
 
 declare_clippy_lint! {
     /// ### What it does
@@ -87,6 +87,7 @@ impl<'tcx> LateLintPass<'tcx> for UseSelf {
             // skip over `ItemKind::OpaqueTy` in order to lint `foo() -> impl <..>`
             return;
         }
+
         // We push the self types of `impl`s on a stack here. Only the top type on the stack is
         // relevant for linting, since this is the self type of the `impl` we're currently in. To
         // avoid linting on nested items, we push `StackItem::NoCheck` on the stack to signal, that
@@ -134,14 +135,17 @@ impl<'tcx> LateLintPass<'tcx> for UseSelf {
     }
 
     fn check_impl_item(&mut self, cx: &LateContext<'_>, impl_item: &hir::ImplItem<'_>) {
+        let Some(&mut StackItem::Check {
+            impl_id,
+            ref mut types_to_skip,
+            ..
+        }) = self.stack.last_mut()
+        else {
+            return;
+        };
         // We want to skip types in trait `impl`s that aren't declared as `Self` in the trait
         // declaration. The collection of those types is all this method implementation does.
         if let ImplItemKind::Fn(FnSig { decl, .. }, ..) = impl_item.kind
-            && let Some(&mut StackItem::Check {
-                impl_id,
-                ref mut types_to_skip,
-                ..
-            }) = self.stack.last_mut()
             && let Some(impl_trait_ref) = cx.tcx.impl_trait_ref(impl_id)
         {
             // `self_ty` is the semantic self type of `impl <trait> for <type>`. This cannot be
@@ -187,8 +191,25 @@ impl<'tcx> LateLintPass<'tcx> for UseSelf {
                 }
             }
         }
+        // Checking const items of `impl Self` blocks in which `std::thread_local!` expands into.
+        // HACK: `std::thread_local_inner` sometimes clears `macro_backtrace` of types in `check_ty`.
+        // To work around this problem, and assume that `LateLintPass` walks recursively from
+        // `check_impl_item` into `check_ty`, `check_expr`,etc. We encode the state when we enter
+        // this const item of `thread_local!` macro. Just remember to remove this state again in
+        // `check_impl_item_post`.
+        else if let ImplItemKind::Const(..) = impl_item.kind
+            && cx.tcx.impl_trait_ref(impl_id).is_none()
+            && is_inside_thread_local_macro(cx, impl_item.span)
+        {
+            self.stack.push(StackItem::NoCheck);
+        }
     }
 
+    fn check_impl_item_post(&mut self, _: &LateContext<'_>, _: &hir::ImplItem<'_>) {
+        if let Some(StackItem::NoCheck) = self.stack.last() {
+            self.stack.pop();
+        }
+    }
 
     fn check_ty(&mut self, cx: &LateContext<'tcx>, hir_ty: &Ty<'tcx>) {
         if !hir_ty.span.from_expansion()
@@ -335,3 +356,11 @@ fn has_no_lifetime(ty: MiddleTy<'_>) -> bool {
         _ => true,
     }
 }
+
+fn is_inside_thread_local_macro(cx: &LateContext<'_>, span: Span) -> bool {
+    if let Some(macro_def_id) = span.source_callee().and_then(|expn| expn.macro_def_id) {
+        cx.tcx.is_diagnostic_item(sym::thread_local_macro, macro_def_id)
+    } else {
+        false
+    }
+}

tests/ui/use_self.fixed

@@ -675,7 +675,7 @@ mod issue_13092 {
 
     impl MyStruct {
         thread_local! {
-            static SPECIAL: RefCell<Self> = RefCell::default();
+            static SPECIAL: RefCell<MyStruct> = RefCell::default();
         }
     }
 }

tests/ui/use_self.stderr

@@ -259,19 +259,5 @@ error: unnecessary structure name repetition
 LL |                 E::A => {},
    |                 ^ help: use the applicable keyword: `Self`
 
-error: unnecessary structure name repetition
-  --> tests/ui/use_self.rs:678:37
-   |
-LL |             static SPECIAL: RefCell<MyStruct> = RefCell::default();
-   |                                     ^^^^^^^^ help: use the applicable keyword: `Self`
-
-error: unnecessary structure name repetition
-  --> tests/ui/use_self.rs:678:37
-   |
-LL |             static SPECIAL: RefCell<MyStruct> = RefCell::default();
-   |                                     ^^^^^^^^ help: use the applicable keyword: `Self`
-   |
-   = note: duplicate diagnostic emitted due to `-Z deduplicate-diagnostics=no`
-
-error: aborting due to 45 previous errors
+error: aborting due to 43 previous errors