Fix use_self ICE

clippy_lints/src/use_self.rs

@@ -87,11 +87,8 @@ const SEGMENTS_MSG: &str = "segments should be composed of at least 1 element";
 
 impl<'tcx> LateLintPass<'tcx> for UseSelf {
     fn check_item(&mut self, _cx: &LateContext<'_>, item: &Item<'_>) {
-        if !is_item_interesting(item) {
-            // This does two things:
-            //  1) Reduce needless churn on `self.stack`
-            //  2) Don't push `StackItem::NoCheck` when entering `ItemKind::OpaqueTy`,
-            //     in order to lint `foo() -> impl <..>`
+        if matches!(item.kind, ItemKind::OpaqueTy(_)) {
+            // 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
@@ -119,7 +116,7 @@ impl<'tcx> LateLintPass<'tcx> for UseSelf {
     }
 
     fn check_item_post(&mut self, _: &LateContext<'_>, item: &Item<'_>) {
-        if is_item_interesting(item) {
+        if !matches!(item.kind, ItemKind::OpaqueTy(_)) {
             self.stack.pop();
         }
     }
@@ -297,11 +294,3 @@ fn lint_path_to_variant(cx: &LateContext<'_>, path: &Path<'_>) {
         span_lint(cx, span);
     }
 }
-
-fn is_item_interesting(item: &Item<'_>) -> bool {
-    use rustc_hir::ItemKind::{Const, Enum, Fn, Impl, Static, Struct, Trait, Union};
-    matches!(
-        item.kind,
-        Impl { .. } | Static(..) | Const(..) | Fn(..) | Enum(..) | Struct(..) | Union(..) | Trait(..)
-    )
-}

tests/ui/crashes/ice-7423.rs

@@ -0,0 +1,13 @@
+pub trait Trait {
+    fn f();
+}
+
+impl Trait for usize {
+    fn f() {
+        extern "C" {
+            fn g() -> usize;
+        }
+    }
+}
+
+fn main() {}