Merge #3357

3357: Check existential types in `use_self` r=oli-obk a=HMPerson1

Fixes #3231

Co-authored-by: HMPerson1 <hmperson1@gmail.com>

clippy_lints/src/use_self.rs

@@ -226,6 +226,6 @@ fn visit_path(&mut self, path: &'tcx Path, _id: HirId) {
     }
 
     fn nested_visit_map<'this>(&'this mut self) -> NestedVisitorMap<'this, 'tcx> {
-        NestedVisitorMap::OnlyBodies(&self.cx.tcx.hir)
+        NestedVisitorMap::All(&self.cx.tcx.hir)
     }
 }

tests/ui/use_self.rs

@@ -205,3 +205,17 @@ fn into_bytes(&self) -> Vec<u8> {
         }
     }
 }
+
+mod existential {
+    struct Foo;
+
+    impl Foo {
+        fn bad(foos: &[Self]) -> impl Iterator<Item=&Foo> {
+            foos.iter()
+        }
+
+        fn good(foos: &[Self]) -> impl Iterator<Item=&Self> {
+            foos.iter()
+        }
+    }
+}

tests/ui/use_self.stderr

@@ -120,5 +120,11 @@ error: unnecessary structure name repetition
 119 |         fn mul(self, rhs: Bad) -> Bad {
     |                                   ^^^ help: use the applicable keyword: `Self`
 
-error: aborting due to 20 previous errors
+error: unnecessary structure name repetition
+   --> $DIR/use_self.rs:213:54
+    |
+213 |         fn bad(foos: &[Self]) -> impl Iterator<Item=&Foo> {
+    |                                                      ^^^ help: use the applicable keyword: `Self`
+
+error: aborting due to 21 previous errors