[Clang] Skip shadow warnings for enum constants in distinct class scopes (#115656)

Fixes #62588

Author: a-tarasyuk

clang/docs/ReleaseNotes.rst

@@ -537,6 +537,8 @@ Improvements to Clang's diagnostics
 
 - Improved diagnostic message for ``__builtin_bit_cast`` size mismatch (#GH115870).
 
+- Clang now omits shadow warnings for enum constants in separate class scopes (#GH62588).
+
 Improvements to Clang's time-trace
 ----------------------------------
 

clang/lib/Sema/SemaDecl.cpp

@@ -8350,9 +8350,15 @@ void Sema::CheckShadow(NamedDecl *D, NamedDecl *ShadowedDecl,
     return;
 
   // Only warn about certain kinds of shadowing for class members.
-  if (NewDC && NewDC->isRecord()) {
+  if (NewDC) {
     // In particular, don't warn about shadowing non-class members.
-    if (!OldDC->isRecord())
+    if (NewDC->isRecord() && !OldDC->isRecord())
+      return;
+
+    // Skip shadowing check if we're in a class scope, dealing with an enum
+    // constant in a different context.
+    DeclContext *ReDC = NewDC->getRedeclContext();
+    if (ReDC->isRecord() && isa<EnumConstantDecl>(D) && !OldDC->Equals(ReDC))
       return;
 
     // TODO: should we warn about static data members shadowing
@@ -8363,7 +8369,6 @@ void Sema::CheckShadow(NamedDecl *D, NamedDecl *ShadowedDecl,
     // shadowing context, but that's just a false negative.
   }
 
-
   DeclarationName Name = R.getLookupName();
 
   // Emit warning and note.

clang/test/SemaCXX/warn-shadow.cpp

@@ -307,3 +307,17 @@ void test4() {
 }
 
 }; // namespace structured_binding_tests
+
+namespace GH62588 {
+class Outer {
+public:
+  char *foo();          // expected-note {{previous declaration is here}} \
+                        // expected-note {{previous definition is here}}
+  enum Outer_E { foo }; // expected-error {{redefinition of 'foo'}} \
+                        // expected-warning {{declaration shadows a static data member of 'GH62588::Outer'}}
+  class Inner {
+  public:
+    enum Inner_E { foo }; // ok
+  };
+};
+} // namespace GH62588