[modules] Don't diagnose a conflict between two using-declarations that name equivalent internal linkage entities.

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@257512 91177308-0d34-0410-b5e6-96231b3b80d8

lib/Sema/SemaDeclCXX.cpp

@@ -7797,6 +7797,10 @@ bool Sema::CheckUsingShadowDecl(UsingDecl *Using, NamedDecl *Orig,
       if (UsingShadowDecl *Shadow = dyn_cast<UsingShadowDecl>(*I))
         PrevShadow = Shadow;
       FoundEquivalentDecl = true;
+    } else if (isEquivalentInternalLinkageDeclaration(D, Target)) {
+      // We don't conflict with an existing using shadow decl of an equivalent
+      // declaration, but we're not a redeclaration of it.
+      FoundEquivalentDecl = true;
     }
 
     if (isVisible(D))

test/Modules/Inputs/using-decl-redecl/a.h

@@ -1,2 +1,3 @@
 struct string {};
-namespace N { typedef ::string clstring; }
+const int n = 0;
+namespace N { typedef ::string clstring; using ::n; }

test/Modules/Inputs/using-decl-redecl/d.h

@@ -0,0 +1 @@
+#include "a.h"

test/Modules/Inputs/using-decl-redecl/module.modulemap

@@ -1,3 +1,4 @@
 module a { header "a.h" }
-module b { header "b.h" export * }
-module c { header "c.h" export * }
+module b { header "b.h" export a }
+module c { header "c.h" export a export b }
+module d { header "d.h" }

test/Modules/using-decl-redecl.cpp

@@ -2,10 +2,20 @@
 // RUN: %clang_cc1 -fmodules -fmodules-cache-path=%t \
 // RUN:            -fmodule-map-file=%S/Inputs/using-decl-redecl/module.modulemap \
 // RUN:            -I%S/Inputs/using-decl-redecl \
+// RUN:            -Wno-modules-ambiguous-internal-linkage \
 // RUN:            -verify %s
+
+#include "d.h"
+
+const int n = 0;
+namespace M { using ::n; }
+
 #include "c.h"
+
 N::clstring y = b;
 
 // Use a typo to trigger import of all declarations in N.
 N::clstrinh s; // expected-error {{did you mean 'clstring'}}
-// expected-note@a.h:2 {{here}}
+// expected-note@a.h:3 {{here}}
+
+namespace M { using N::n; }