[Clang][Sema] Skip RecordDecl when checking scope of declarations (llvm#69432)

In non C++ mode, struct definitions does not create a scope for
declaration.

Author: ecnelises

clang/docs/ReleaseNotes.rst

@@ -712,6 +712,8 @@ Miscellaneous Clang Crashes Fixed
   `Issue 64564 <https://github.com/llvm/llvm-project/issues/64564>`_
 - Fixed a crash when an ObjC ivar has an invalid type. See
   (`#68001 <https://github.com/llvm/llvm-project/pull/68001>`_)
+- Fixed a crash in C when redefined struct is another nested redefinition.
+  `Issue 41302 <https://github.com/llvm/llvm-project/issues/41302>`_
 
 Target Specific Changes
 -----------------------

clang/lib/Sema/IdentifierResolver.cpp

@@ -109,7 +109,9 @@ bool IdentifierResolver::isDeclInScope(Decl *D, DeclContext *Ctx, Scope *S,
     return false;
   if (Ctx->isFunctionOrMethod() || (S && S->isFunctionPrototypeScope())) {
     // Ignore the scopes associated within transparent declaration contexts.
-    while (S->getEntity() && S->getEntity()->isTransparentContext())
+    while (S->getEntity() &&
+           (S->getEntity()->isTransparentContext() ||
+            (!LangOpt.CPlusPlus && isa<RecordDecl>(S->getEntity()))))
       S = S->getParent();
 
     if (S->isDeclScope(D))

clang/test/Sema/nested-redef.c

@@ -19,4 +19,16 @@ void f2(void) {
   struct U u;
 }
 
+void f3(void) {
+  struct G { // expected-note{{previous definition is here}}
+    struct G {}; // expected-error{{nested redefinition of 'G'}}
+  };
+}
+
+void f4(void) {
+  struct G { // expected-note 2{{previous definition is here}}
+    struct G {}; // expected-error{{nested redefinition of 'G'}}
+  };
 
+  struct G {}; // expected-error{{redefinition of 'G'}}
+}

clang/test/SemaObjC/ivar-lookup.m

@@ -95,11 +95,11 @@ - (int) test
   union U {
     __typeof(myStatus) __in;  // fails.
   };
-  struct S {
+  struct S { // expected-note{{previous definition is here}}
     __typeof(myStatus) __in;  // fails.
     struct S1 { // expected-warning {{declaration does not declare anything}}
       __typeof(myStatus) __in;  // fails.
-      struct S { // expected-warning {{declaration does not declare anything}}
+      struct S { // expected-error {{nested redefinition of 'S'}}
         __typeof(myStatus) __in;  // fails.
       };
     };