Test "merging" of typedef types across distinct modules. At present,

the AST reader doesn't actually perform a merge, because name lookup
knows how to merge identical typedefs together.

As part of this, teach C/Objective-C name lookup to return multiple
results in all cases, rather than first digging through the attributes
to see if the value is overloadable. This way, we'll catch ambiguous
lookups in C/Objective-C.

llvm-svn: 147498

clang/lib/AST/Decl.cpp

@@ -938,6 +938,12 @@ bool NamedDecl::declarationReplaces(NamedDecl *OldD) const {
                                         cast<UsingDecl>(OldD)->getQualifier());
   }
 
+  // A typedef of an Objective-C class type can replace an Objective-C class
+  // declaration or definition, and vice versa.
+  if ((isa<TypedefNameDecl>(this) && isa<ObjCInterfaceDecl>(OldD)) ||
+      (isa<ObjCInterfaceDecl>(this) && isa<TypedefNameDecl>(OldD)))
+    return true;
+  
   // For non-function declarations, if the declarations are of the
   // same kind then this must be a redeclaration, or semantic analysis
   // would not have given us the new declaration.

clang/lib/Sema/SemaDecl.cpp

@@ -8010,8 +8010,6 @@ Decl *Sema::ActOnTag(Scope *S, unsigned TagSpec, TagUseKind TUK,
     // lookup.  This is only actually possible in C++, where a few
     // things like templates still live in the tag namespace.
     } else {
-      assert(getLangOptions().CPlusPlus);
-
       // Use a better diagnostic if an elaborated-type-specifier
       // found the wrong kind of type on the first
       // (non-redeclaration) lookup.

clang/lib/Sema/SemaLookup.cpp

@@ -1177,13 +1177,13 @@ bool Sema::LookupName(LookupResult &R, Scope *S, bool AllowBuiltinCreation) {
                 
         R.addDecl(D);
 
-        if ((*I)->getAttr<OverloadableAttr>()) {
-          // If this declaration has the "overloadable" attribute, we
-          // might have a set of overloaded functions.
+        // Check whether there are any other declarations with the same name
+        // and in the same scope.
 
         // Figure out what scope the identifier is in.
-          while (!(S->getFlags() & Scope::DeclScope) ||
-                 !S->isDeclScope(*I))
+        while (S->getParent() &&
+               (!(S->getFlags() & Scope::DeclScope) ||
+                !S->isDeclScope(*I)))
           S = S->getParent();
 
         // Find the last declaration in this scope (with the same
@@ -1193,14 +1193,15 @@ bool Sema::LookupName(LookupResult &R, Scope *S, bool AllowBuiltinCreation) {
           if (!S->isDeclScope(*LastI))
             break;
           
+          if (!(*LastI)->isInIdentifierNamespace(IDNS))
+            continue;
+          
           D = getVisibleDecl(*LastI);
           if (D)
             R.addDecl(D);
         }
-        }
 
         R.resolveKind();
-
         return true;
       }
   } else {

clang/test/Modules/Inputs/redecl-merge-left.h

@@ -56,6 +56,9 @@ struct S4 {
 struct S3 *produce_S3(void);
 void consume_S4(struct S4*);
 
+typedef int T1;
+typedef float T2;
+
 #ifdef __cplusplus
 template<typename T> class Vector;
 

clang/test/Modules/Inputs/redecl-merge-right.h

@@ -59,6 +59,9 @@ struct S4;
 void consume_S3(struct S3*);
 struct S4 *produce_S4(void);
 
+typedef int T1;
+typedef double T2;
+
 #ifdef __cplusplus
 template<typename T> class Vector { 
 public:

clang/test/Modules/redecl-merge.m

@@ -55,6 +55,15 @@ void testTagMerge() {
   s3.s3_field = 0;
 }
 
+void testTypedefMerge(int i, double d) {
+  T1 *ip = &i;
+  // in other file: expected-note{{candidate found by name lookup is 'T2'}}
+  // FIXME: Typedefs aren't actually merged in the sense of other merges, because
+  // we should only merge them when the types are identical.
+  // in other file: expected-note{{candidate found by name lookup is 'T2'}}
+  T2 *dp = &d; // expected-error{{reference to 'T2' is ambiguous}}
+}
+
 // Test redeclarations of entities in explicit submodules, to make
 // sure we're maintaining the declaration chains even when normal name
 // lookup can't see what we're looking for.