Add semantic analysis for the creation of and an AST representation

for template template argument pack expansions. This allows fun such
as: 

  template<template<class> class ...> struct apply_impl { /*...*/ };
  template<template<class> class ...Metafunctions> struct apply {
    typedef typename apply_impl<Metafunctions...>::type type;
  };

However, neither template argument deduction nor template
instantiation is implemented for template template argument packs, so
this functionality isn't useful yet.

I'll probably replace the encoding of template template
argument pack expansions in TemplateArgument so that it's harder to
accidentally forget about the expansion. However, this is a step in
the right general direction.

llvm-svn: 122890

1 files changed, 41 insertions, 31 deletions

diff --git a/clang/lib/AST/TemplateBase.cpp b/clang/lib/AST/TemplateBase.cpp
index c9715199612..6eae6a4192f 100644
--- a/clang/lib/AST/TemplateBase.cpp
+++ b/clang/lib/AST/TemplateBase.cpp
@@ -76,8 +76,7 @@ bool TemplateArgument::isPackExpansion() const {
     return isa<PackExpansionType>(getAsType());
       
   case Template:
-    // FIXME: Template template pack expansions.
-    break;
+    return TemplateArg.PackExpansion;
     
   case Expression:
     return isa<PackExpansionExpr>(getAsExpr());
@@ -99,7 +98,8 @@ bool TemplateArgument::containsUnexpandedParameterPack() const {
     break;
 
   case Template:
-    if (getAsTemplate().containsUnexpandedParameterPack())
+    if (!TemplateArg.PackExpansion && 
+        getAsTemplate().containsUnexpandedParameterPack())
       return true;
     break;
         
@@ -135,12 +135,14 @@ void TemplateArgument::Profile(llvm::FoldingSetNodeID &ID,
     break;
 
   case Template:
+    ID.AddBoolean(TemplateArg.PackExpansion);
     if (TemplateTemplateParmDecl *TTP
           = dyn_cast_or_null<TemplateTemplateParmDecl>(
                                        getAsTemplate().getAsTemplateDecl())) {
       ID.AddBoolean(true);
       ID.AddInteger(TTP->getDepth());
       ID.AddInteger(TTP->getPosition());
+      ID.AddBoolean(TTP->isParameterPack());
     } else {
       ID.AddBoolean(false);
       ID.AddPointer(Context.getCanonicalTemplateName(getAsTemplate())
@@ -171,10 +173,13 @@ bool TemplateArgument::structurallyEquals(const TemplateArgument &Other) const {
   case Null:
   case Type:
   case Declaration:
-  case Template:
   case Expression:
     return TypeOrValue == Other.TypeOrValue;
 
+  case Template:
+    return TemplateArg.Template == Other.TemplateArg.Template &&
+           TemplateArg.PackExpansion == Other.TemplateArg.PackExpansion;
+      
   case Integral:
     return getIntegralType() == Other.getIntegralType() &&
            *getAsIntegral() == *Other.getAsIntegral();
@@ -195,21 +200,20 @@ TemplateArgument TemplateArgument::getPackExpansionPattern() const {
   assert(isPackExpansion());
   
   switch (getKind()) {
-    case Type:
-      return getAsType()->getAs<PackExpansionType>()->getPattern();
-      
-    case Expression:
-      return cast<PackExpansionExpr>(getAsExpr())->getPattern();
-      
-    case Template:
-      // FIXME: Variadic templates.
-      llvm_unreachable("Template pack expansions unsupported");
-      
-    case Declaration:
-    case Integral:
-    case Pack:
-    case Null:
-      return TemplateArgument();
+  case Type:
+    return getAsType()->getAs<PackExpansionType>()->getPattern();
+    
+  case Expression:
+    return cast<PackExpansionExpr>(getAsExpr())->getPattern();
+    
+  case Template:
+    return TemplateArgument(getAsTemplate(), false);
+    
+  case Declaration:
+  case Integral:
+  case Pack:
+  case Null:
+    return TemplateArgument();
   }
   
   return TemplateArgument();
@@ -246,6 +250,8 @@ void TemplateArgument::print(const PrintingPolicy &Policy,
     
   case Template: {
     getAsTemplate().print(Out, Policy);
+    if (TemplateArg.PackExpansion)
+      Out << "...";
     break;
   }
     
@@ -254,12 +260,9 @@ void TemplateArgument::print(const PrintingPolicy &Policy,
     break;
   }
     
-  case Expression: {
-    // FIXME: This is non-optimal, since we're regurgitating the
-    // expression we were given.
+  case Expression:
     getAsExpr()->printPretty(Out, 0, Policy);
     break;
-  }
     
   case Pack:
     Out << "<";
@@ -296,12 +299,15 @@ SourceRange TemplateArgumentLoc::getSourceRange() const {
     else
       return SourceRange();
 
-  case TemplateArgument::Template:
+  case TemplateArgument::Template: {
+    SourceLocation End = getTemplateNameLoc();
+    if (getTemplateEllipsisLoc().isValid())
+      End = getTemplateEllipsisLoc();
     if (getTemplateQualifierRange().isValid())
-      return SourceRange(getTemplateQualifierRange().getBegin(),
-                         getTemplateNameLoc());
-    return SourceRange(getTemplateNameLoc());
-
+      return SourceRange(getTemplateQualifierRange().getBegin(), End);
+    return SourceRange(getTemplateNameLoc(), End);
+  }
+      
   case TemplateArgument::Integral:
   case TemplateArgument::Pack:
   case TemplateArgument::Null:
@@ -351,8 +357,9 @@ TemplateArgumentLoc::getPackExpansionPattern(SourceLocation &Ellipsis,
   }
       
   case TemplateArgument::Template:
-    // FIXME: Variadic templates.
-      llvm_unreachable("Template pack expansions unsupported");
+    return TemplateArgumentLoc(Argument.getPackExpansionPattern(),
+                               getTemplateQualifierRange(),
+                               getTemplateNameLoc());
     
   case TemplateArgument::Declaration:
   case TemplateArgument::Integral:
@@ -382,7 +389,10 @@ const DiagnosticBuilder &clang::operator<<(const DiagnosticBuilder &DB,
     return DB << Arg.getAsIntegral()->toString(10);
       
   case TemplateArgument::Template:
-    return DB << Arg.getAsTemplate();
+    DB << Arg.getAsTemplate();
+    if (Arg.isPackExpansion())
+      DB << "...";
+    return DB;
       
   case TemplateArgument::Expression: {
     // This shouldn't actually ever happen, so it's okay that we're