Auto merge of #140406 - Urgau:autorefs-perf, r=nnethercote

perf: delay checking of `#[rustc_no_implicit_autorefs]` in autoref lint

Try to address the regression seen in https://github.com/rust-lang/rust/pull/123239#issuecomment-2835418470 by delaying the checking of `#[rustc_no_implicit_autorefs]` on method call.

1 files changed, 11 insertions, 4 deletions

diff --git a/compiler/rustc_lint/src/autorefs.rs b/compiler/rustc_lint/src/autorefs.rs
index 5dd26854c95..ddab13190be 100644
--- a/compiler/rustc_lint/src/autorefs.rs
+++ b/compiler/rustc_lint/src/autorefs.rs
@@ -75,10 +75,9 @@ impl<'tcx> LateLintPass<'tcx> for ImplicitAutorefs {
                 _ => return,
             },
             ExprKind::Index(base, _, _) => base,
-            ExprKind::MethodCall(_, inner, _, _)
-                if let Some(def_id) = cx.typeck_results().type_dependent_def_id(expr.hir_id)
-                    && cx.tcx.has_attr(def_id, sym::rustc_no_implicit_autorefs) =>
-            {
+            ExprKind::MethodCall(_, inner, _, _) => {
+                // PERF: Checking of `#[rustc_no_implicit_refs]` is deferred below
+                // because checking for attribute is a bit costly.
                 inner
             }
             ExprKind::Field(inner, _) => inner,
@@ -99,6 +98,14 @@ impl<'tcx> LateLintPass<'tcx> for ImplicitAutorefs {
                 peel_place_mappers(inner).kind
             // 1. Deref of a raw pointer.
             && typeck.expr_ty(dereferenced).is_raw_ptr()
+            // PERF: 5. b. A method call annotated with `#[rustc_no_implicit_refs]`
+            && match expr.kind {
+                ExprKind::MethodCall(..) => matches!(
+                    cx.typeck_results().type_dependent_def_id(expr.hir_id),
+                    Some(def_id) if cx.tcx.has_attr(def_id, sym::rustc_no_implicit_autorefs)
+                ),
+                _ => true,
+            }
         {
             cx.emit_span_lint(
                 DANGEROUS_IMPLICIT_AUTOREFS,