Fix PR16060.

The testcase in PR16060 points out that while template arguments can
show that a type is not externally visible, the standards still says
they have external linkage.

In terms of our implementation, it means that we should merge just the
isExternallyVisible bit, not the formal linkage.

llvm-svn: 182962

clang/include/clang/Basic/Visibility.h

@@ -89,6 +89,20 @@ public:
     mergeLinkage(other.getLinkage());
   }
 
+  void mergeExternalVisibility(Linkage L) {
+    Linkage ThisL = getLinkage();
+    if (!isExternallyVisible(L)) {
+      if (ThisL == VisibleNoLinkage)
+        ThisL = NoLinkage;
+      else if (ThisL == ExternalLinkage)
+        ThisL = UniqueExternalLinkage;
+    }
+    setLinkage(ThisL);
+  }
+  void mergeExternalVisibility(LinkageInfo Other) {
+    mergeExternalVisibility(Other.getLinkage());
+  }
+
   /// Merge in the visibility 'newVis'.
   void mergeVisibility(Visibility newVis, bool newExplicit) {
     Visibility oldVis = getVisibility();

clang/lib/AST/Decl.cpp

@@ -471,7 +471,9 @@ static void mergeTemplateLV(LinkageInfo &LV,
   // instantiation with a visibility attribute.
   const TemplateArgumentList &templateArgs = spec->getTemplateArgs();
   LinkageInfo argsLV = getLVForTemplateArgumentList(templateArgs, computation);
-  LV.mergeMaybeWithVisibility(argsLV, considerVisibility);
+  if (considerVisibility)
+    LV.mergeVisibility(argsLV);
+  LV.mergeExternalVisibility(argsLV);
 }
 
 static bool useInlineVisibilityHidden(const NamedDecl *D) {
@@ -863,8 +865,9 @@ static LinkageInfo getLVForClassMember(const NamedDecl *D,
     // Modify the variable's linkage by its type, but ignore the
     // type's visibility unless it's a definition.
     LinkageInfo typeLV = getLVForType(*VD->getType(), computation);
-    LV.mergeMaybeWithVisibility(typeLV,
+    if (!LV.isVisibilityExplicit() && !classLV.isVisibilityExplicit())
-                 !LV.isVisibilityExplicit() && !classLV.isVisibilityExplicit());
+      LV.mergeVisibility(typeLV);
+    LV.mergeExternalVisibility(typeLV);
 
     if (isExplicitMemberSpecialization(VD)) {
       explicitSpecSuppressor = VD;

clang/test/SemaCXX/linkage2.cpp

@@ -186,3 +186,18 @@ namespace test17 {
     g();
   }
 }
+
+namespace test18 {
+  template <typename T> struct foo {
+    template <T *P> static void f() {}
+    static void *g() { return (void *)f<&x>; }
+    static T x;
+  };
+  template <typename T> T foo<T>::x;
+  inline void *f() {
+    struct S {
+    };
+    return foo<S>::g();
+  }
+  void *h() { return f(); }
+}