PR20769: Fix confusion when checking whether a prior default argument was in

scope when checking for conflicts.

llvm-svn: 216628

2 files changed, 13 insertions, 6 deletions

diff --git a/clang/lib/Sema/IdentifierResolver.cpp b/clang/lib/Sema/IdentifierResolver.cpp
index 2a5bacff0d9..6586fb32787 100644
--- a/clang/lib/Sema/IdentifierResolver.cpp
+++ b/clang/lib/Sema/IdentifierResolver.cpp
@@ -130,6 +130,9 @@ bool IdentifierResolver::isDeclInScope(Decl *D, DeclContext *Ctx, Scope *S,
     return false;
   }
 
+  // FIXME: If D is a local extern declaration, this check doesn't make sense;
+  // we should be checking its lexical context instead in that case, because
+  // that is its scope.
   DeclContext *DCtx = D->getDeclContext()->getRedeclContext();
   return AllowInlineNamespace ? Ctx->InEnclosingNamespaceSetOf(DCtx)
                               : Ctx->Equals(DCtx);
diff --git a/clang/lib/Sema/SemaDeclCXX.cpp b/clang/lib/Sema/SemaDeclCXX.cpp
index 081d91e0506..f0925e478b1 100644
--- a/clang/lib/Sema/SemaDeclCXX.cpp
+++ b/clang/lib/Sema/SemaDeclCXX.cpp
@@ -446,20 +446,24 @@ bool Sema::MergeCXXFunctionDecl(FunctionDecl *New, FunctionDecl *Old,
     bool OldParamHasDfl = OldParam->hasDefaultArg();
     bool NewParamHasDfl = NewParam->hasDefaultArg();
 
-    NamedDecl *ND = Old;
-
     // The declaration context corresponding to the scope is the semantic
     // parent, unless this is a local function declaration, in which case
     // it is that surrounding function.
-    DeclContext *ScopeDC = New->getLexicalDeclContext();
-    if (!ScopeDC->isFunctionOrMethod())
-      ScopeDC = New->getDeclContext();
-    if (S && !isDeclInScope(ND, ScopeDC, S) &&
+    DeclContext *ScopeDC = New->isLocalExternDecl()
+                               ? New->getLexicalDeclContext()
+                               : New->getDeclContext();
+    if (S && !isDeclInScope(Old, ScopeDC, S) &&
         !New->getDeclContext()->isRecord())
       // Ignore default parameters of old decl if they are not in
       // the same scope and this is not an out-of-line definition of
       // a member function.
       OldParamHasDfl = false;
+    if (New->isLocalExternDecl() != Old->isLocalExternDecl())
+      // If only one of these is a local function declaration, then they are
+      // declared in different scopes, even though isDeclInScope may think
+      // they're in the same scope. (If both are local, the scope check is
+      // sufficent, and if neither is local, then they are in the same scope.)
+      OldParamHasDfl = false;
 
     if (OldParamHasDfl && NewParamHasDfl) {