When a pack expansion occurs in the template argument list of an alias

template without a corresponding parameter pack, don't immediately
substitute the alias template. This is under discussion in the C++
committee, and may become ill-formed, but for now we match GCC.



git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@149697 91177308-0d34-0410-b5e6-96231b3b80d8

1 files changed, 14 insertions, 5 deletions

diff --git a/lib/Sema/SemaTemplate.cpp b/lib/Sema/SemaTemplate.cpp
index 7cd604d585..eca491f733 100644
--- a/lib/Sema/SemaTemplate.cpp
+++ b/lib/Sema/SemaTemplate.cpp
@@ -1918,15 +1918,17 @@ QualType Sema::CheckTemplateIdType(TemplateName Name,
   // Check that the template argument list is well-formed for this
   // template.
   SmallVector<TemplateArgument, 4> Converted;
+  bool ExpansionIntoFixedList = false;
   if (CheckTemplateArgumentList(Template, TemplateLoc, TemplateArgs,
-                                false, Converted))
+                                false, Converted, &ExpansionIntoFixedList))
     return QualType();
 
   QualType CanonType;
 
   bool InstantiationDependent = false;
-  if (TypeAliasTemplateDecl *AliasTemplate
-        = dyn_cast<TypeAliasTemplateDecl>(Template)) {
+  TypeAliasTemplateDecl *AliasTemplate = 0;
+  if (!ExpansionIntoFixedList &&
+      (AliasTemplate = dyn_cast<TypeAliasTemplateDecl>(Template))) {
     // Find the canonical type for this type alias template specialization.
     TypeAliasDecl *Pattern = AliasTemplate->getTemplatedDecl();
     if (Pattern->isInvalidDecl())
@@ -2891,7 +2893,11 @@ bool Sema::CheckTemplateArgumentList(TemplateDecl *Template,
                                      SourceLocation TemplateLoc,
                                      TemplateArgumentListInfo &TemplateArgs,
                                      bool PartialTemplateArgs,
-                          SmallVectorImpl<TemplateArgument> &Converted) {
+                          SmallVectorImpl<TemplateArgument> &Converted,
+                                     bool *ExpansionIntoFixedList) {
+  if (ExpansionIntoFixedList)
+    *ExpansionIntoFixedList = false;
+
   TemplateParameterList *Params = Template->getTemplateParameters();
   unsigned NumParams = Params->size();
   unsigned NumArgs = TemplateArgs.size();
@@ -2901,7 +2907,7 @@ bool Sema::CheckTemplateArgumentList(TemplateDecl *Template,
 
   bool HasParameterPack =
     NumParams > 0 && Params->getParam(NumParams - 1)->isTemplateParameterPack();
-
+  
   // C++ [temp.arg]p1:
   //   [...] The type and form of each template-argument specified in
   //   a template-id shall match the type and form specified for the
@@ -3088,6 +3094,9 @@ bool Sema::CheckTemplateArgumentList(TemplateDecl *Template,
                                            ArgumentPack.size()));
         ArgumentPack.clear();
       }      
+    } else if (ExpansionIntoFixedList) {
+      // We have expanded a pack into a fixed list.
+      *ExpansionIntoFixedList = true;
     }
 
     return Invalid;