commit f463436d9c02deb870f2ecbba4a69a96f6f9b3d7
author Richard Smith <richard-llvm@metafoo.co.uk> Wed Sep 03 23:11:22 2014 +0000
committer Richard Smith <richard-llvm@metafoo.co.uk> Wed Sep 03 23:11:22 2014 +0000
tree 5810630f0ac6f5e0529de79d06c3179787871727
parent c6ab01eccae05aee4bae81a875a6eb88907247c5

[modules] Make NamespaceAliasDecl redeclarable, as it should be. This fixes
merging of namespace aliases across modules and improves source fidelity.
Incidentally also fixes PR20816.

llvm-svn: 217103

clang/lib/Sema/SemaDeclCXX.cpp

diff --git a/clang/lib/Sema/SemaDeclCXX.cpp b/clang/lib/Sema/SemaDeclCXX.cpp
index 5da6546..858f2c7 100644
--- a/clang/lib/Sema/SemaDeclCXX.cpp
+++ b/clang/lib/Sema/SemaDeclCXX.cpp
@@ -8264,43 +8264,16 @@
   return NewND;
 }
 
-Decl *Sema::ActOnNamespaceAliasDef(Scope *S,
-                                             SourceLocation NamespaceLoc,
-                                             SourceLocation AliasLoc,
-                                             IdentifierInfo *Alias,
-                                             CXXScopeSpec &SS,
-                                             SourceLocation IdentLoc,
-                                             IdentifierInfo *Ident) {
+Decl *Sema::ActOnNamespaceAliasDef(Scope *S, SourceLocation NamespaceLoc,
+                                   SourceLocation AliasLoc,
+                                   IdentifierInfo *Alias, CXXScopeSpec &SS,
+                                   SourceLocation IdentLoc,
+                                   IdentifierInfo *Ident) {
 
   // Lookup the namespace name.
   LookupResult R(*this, Ident, IdentLoc, LookupNamespaceName);
   LookupParsedName(R, S, &SS);
 
-  // Check if we have a previous declaration with the same name.
-  NamedDecl *PrevDecl
-    = LookupSingleName(S, Alias, AliasLoc, LookupOrdinaryName, 
-                       ForRedeclaration);
-  if (PrevDecl && !isDeclInScope(PrevDecl, CurContext, S))
-    PrevDecl = nullptr;
-
-  if (PrevDecl) {
-    if (NamespaceAliasDecl *AD = dyn_cast<NamespaceAliasDecl>(PrevDecl)) {
-      // We already have an alias with the same name that points to the same
-      // namespace, so don't create a new one.
-      // FIXME: At some point, we'll want to create the (redundant)
-      // declaration to maintain better source information.
-      if (!R.isAmbiguous() && !R.empty() &&
-          AD->getNamespace()->Equals(getNamespaceDecl(R.getFoundDecl())))
-        return nullptr;
-    }
-
-    unsigned DiagID = isa<NamespaceDecl>(PrevDecl) ? diag::err_redefinition :
-      diag::err_redefinition_different_kind;
-    Diag(AliasLoc, DiagID) << Alias;
-    Diag(PrevDecl->getLocation(), diag::note_previous_definition);
-    return nullptr;
-  }
-
   if (R.isAmbiguous())
     return nullptr;
 
@@ -8310,11 +8283,41 @@
       return nullptr;
     }
   }
+  assert(!R.isAmbiguous() && !R.empty());
+
+  // Check if we have a previous declaration with the same name.
+  NamedDecl *PrevDecl = LookupSingleName(S, Alias, AliasLoc, LookupOrdinaryName,
+                                         ForRedeclaration);
+  if (PrevDecl && !isDeclInScope(PrevDecl, CurContext, S))
+    PrevDecl = nullptr;
+
+  if (PrevDecl) {
+    if (NamespaceAliasDecl *AD = dyn_cast<NamespaceAliasDecl>(PrevDecl)) {
+      // We already have an alias with the same name that points to the same
+      // namespace; check that it matches.
+      if (!AD->getNamespace()->Equals(getNamespaceDecl(R.getFoundDecl()))) {
+        Diag(AliasLoc, diag::err_redefinition_different_namespace_alias)
+          << Alias;
+        Diag(PrevDecl->getLocation(), diag::note_previous_namespace_alias)
+          << AD->getNamespace();
+        return nullptr;
+      }
+    } else {
+      unsigned DiagID = isa<NamespaceDecl>(PrevDecl)
+                            ? diag::err_redefinition
+                            : diag::err_redefinition_different_kind;
+      Diag(AliasLoc, DiagID) << Alias;
+      Diag(PrevDecl->getLocation(), diag::note_previous_definition);
+      return nullptr;
+    }
+  }
 
   NamespaceAliasDecl *AliasDecl =
     NamespaceAliasDecl::Create(Context, CurContext, NamespaceLoc, AliasLoc,
                                Alias, SS.getWithLocInContext(Context),
                                IdentLoc, R.getFoundDecl());
+  if (PrevDecl)
+    AliasDecl->setPreviousDecl(cast<NamespaceAliasDecl>(PrevDecl));
 
   PushOnScopeChains(AliasDecl, S);
   return AliasDecl;