Variadic templates: extend Type, NestedNameSpecifier, TemplateName,

and TemplateArgument with an operation that determines whether there
are any unexpanded parameter packs within that construct. Use this
information to diagnose the appearance of the names of parameter packs
that have not been expanded (C++ [temp.variadic]p5). Since this
property is checked often (every declaration, ever expression
statement, etc.), we extend Type and Expr with a bit storing the
result of this computation, rather than walking the AST each time to
determine whether any unexpanded parameter packs occur.

This commit is deficient in several ways, which will be remedied with
future commits:
  - Expr has a bit to store the presence of an unexpanded parameter
  pack, but it is never set.
  - The error messages don't point out where the unexpanded parameter
  packs were named in the type/expression, but they should. 
  - We don't check for unexpanded parameter packs in all of the places
  where we should.
  - Testing is sparse, pending the resolution of the above three
  issues.

llvm-svn: 121724

1 files changed, 33 insertions, 0 deletions

diff --git a/clang/lib/AST/TemplateBase.cpp b/clang/lib/AST/TemplateBase.cpp
index 4a1ebb46c1e..ef2deea8c84 100644
--- a/clang/lib/AST/TemplateBase.cpp
+++ b/clang/lib/AST/TemplateBase.cpp
@@ -26,6 +26,39 @@ using namespace clang;
 // TemplateArgument Implementation
 //===----------------------------------------------------------------------===//
 
+bool TemplateArgument::containsUnexpandedParameterPack() const {
+  switch (getKind()) {
+  case Null:
+  case Declaration:
+  case Integral:
+    break;
+
+  case Type:
+    if (getAsType()->containsUnexpandedParameterPack())
+      return true;
+    break;
+
+  case Template:
+    if (getAsTemplate().containsUnexpandedParameterPack())
+      return true;
+    break;
+        
+  case Expression:
+    if (getAsExpr()->containsUnexpandedParameterPack())
+      return true;
+    break;
+
+  case Pack:
+    for (pack_iterator P = pack_begin(), PEnd = pack_end(); P != PEnd; ++P)
+      if (P->containsUnexpandedParameterPack())
+        return true;
+
+    break;
+  }
+
+  return false;
+}
+
 void TemplateArgument::Profile(llvm::FoldingSetNodeID &ID,
                                ASTContext &Context) const {
   ID.AddInteger(Kind);