[modules] Allow "redefinition" of typedef of anon tag from unimported submodule

r233345 started being stricter about typedef names for linkage purposes
in non-visible modules, but broke languages without the ODR.

rdar://23527954

llvm-svn: 253123

clang/lib/AST/Decl.cpp

@@ -1256,7 +1256,8 @@ static LinkageInfo computeLVForDecl(const NamedDecl *D,
     case Decl::TypeAlias:
       // A typedef declaration has linkage if it gives a type a name for
       // linkage purposes.
-      if (!cast<TypedefNameDecl>(D)
+      if (!D->getASTContext().getLangOpts().CPlusPlus ||
+          !cast<TypedefNameDecl>(D)
                ->getAnonDeclWithTypedefName(/*AnyRedecl*/true))
         return LinkageInfo::none();
       break;

clang/lib/Sema/SemaDecl.cpp

@@ -1829,7 +1829,8 @@ static void filterNonConflictingPreviousTypedefDecls(Sema &S,
 
       // If both declarations give a tag declaration a typedef name for linkage
       // purposes, then they declare the same entity.
-      if (OldTD->getAnonDeclWithTypedefName(/*AnyRedecl*/true) &&
+      if (S.getLangOpts().CPlusPlus &&
+          OldTD->getAnonDeclWithTypedefName(/*AnyRedecl*/true) &&
           Decl->getAnonDeclWithTypedefName())
         continue;
     }

clang/test/Index/usrs.m

@@ -119,7 +119,7 @@ int test_multi_declaration(void) {
 // CHECK: usrs.m c:@SA@MyStruct Extent=[15:9 - 18:2]
 // CHECK: usrs.m c:@SA@MyStruct@FI@wa Extent=[16:3 - 16:9]
 // CHECK: usrs.m c:@SA@MyStruct@FI@moo Extent=[17:3 - 17:10]
-// CHECK: usrs.m c:@T@MyStruct Extent=[15:1 - 18:11]
+// CHECK: usrs.m c:usrs.m@T@MyStruct Extent=[15:1 - 18:11]
 // CHECK: usrs.m c:@E@Pizza Extent=[20:1 - 23:2]
 // CHECK: usrs.m c:@E@Pizza@CHEESE Extent=[21:3 - 21:9]
 // CHECK: usrs.m c:@E@Pizza@MUSHROOMS Extent=[22:3 - 22:12]

clang/test/Modules/Inputs/module.map

@@ -379,3 +379,10 @@ module DebugSubmodules {
 module ExtensionTestA {
   header "ExtensionTestA.h"
 }
+
+module TypedefTag {
+  header "typedef-tag.h"
+  explicit module Hidden {
+    header "typedef-tag-hidden.h"
+  }
+}

clang/test/Modules/Inputs/typedef-tag-hidden.h

@@ -0,0 +1 @@
+typedef struct { int x; } TypedefStructHidden_t;

clang/test/Modules/Inputs/typedef-tag.h

@@ -0,0 +1 @@
+typedef struct { int x; } TypedefStructVisible_t;

clang/test/Modules/typedef-tag-not-visible.m

@@ -0,0 +1,8 @@
+// RUN: rm -rf %t
+// RUN: %clang_cc1 -fmodules -fimplicit-module-maps -fmodules-cache-path=%t -I %S/Inputs %s -verify
+
+@import TypedefTag;
+
+typedef struct { int x; } TypedefStructHidden_t;
+typedef struct { int x; } TypedefStructVisible_t; // expected-error{{typedef redefinition}}
+// expected-note@typedef-tag.h:1 {{here}}