From 98440b4ac17dc5f85ea3db683c1c1785449c17e1 Mon Sep 17 00:00:00 2001
From: Douglas Gregor <dgregor@apple.com>
Date: Sat, 21 Nov 2009 02:07:55 +0000
Subject: [PATCH] Implement C++ [temp.param]p2 correctly, looking ahead when we
 see a "typename" parameter to distinguish between non-type and type template
 parameters. Fixes the actual bug in PR5559.

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@89532 91177308-0d34-0410-b5e6-96231b3b80d8
---
 include/clang/Parse/Parser.h    |  1 +
 lib/Parse/ParseTemplate.cpp     | 40 ++++++++++++++++++++++++++++-----
 test/CXX/temp/temp.param/p2.cpp |  3 ++-
 3 files changed, 38 insertions(+), 6 deletions(-)

diff --git a/include/clang/Parse/Parser.h b/include/clang/Parse/Parser.h
index f7ccccac09..814064a79e 100644
--- a/include/clang/Parse/Parser.h
+++ b/include/clang/Parse/Parser.h
@@ -1353,6 +1353,7 @@ private:
                                SourceLocation &RAngleLoc);
   bool ParseTemplateParameterList(unsigned Depth,
                                   TemplateParameterList &TemplateParams);
+  bool isStartOfTemplateTypeParameter();
   DeclPtrTy ParseTemplateParameter(unsigned Depth, unsigned Position);
   DeclPtrTy ParseTypeParameter(unsigned Depth, unsigned Position);
   DeclPtrTy ParseTemplateTemplateParameter(unsigned Depth, unsigned Position);
diff --git a/lib/Parse/ParseTemplate.cpp b/lib/Parse/ParseTemplate.cpp
index 5be4ca82f7..e655dedab4 100644
--- a/lib/Parse/ParseTemplate.cpp
+++ b/lib/Parse/ParseTemplate.cpp
@@ -333,6 +333,40 @@ Parser::ParseTemplateParameterList(unsigned Depth,
   return true;
 }
 
+/// \brief Determine whether the parser is at the start of a template
+/// type parameter.
+bool Parser::isStartOfTemplateTypeParameter() {
+  if (Tok.is(tok::kw_class))
+    return true;
+
+  if (Tok.isNot(tok::kw_typename))
+    return false;
+
+  // C++ [temp.param]p2:
+  //   There is no semantic difference between class and typename in a
+  //   template-parameter. typename followed by an unqualified-id
+  //   names a template type parameter. typename followed by a
+  //   qualified-id denotes the type in a non-type
+  //   parameter-declaration.
+  Token Next = NextToken();
+
+  // If we have an identifier, skip over it.
+  if (Next.getKind() == tok::identifier)
+    Next = GetLookAheadToken(2);
+
+  switch (Next.getKind()) {
+  case tok::equal:
+  case tok::comma:
+  case tok::greater:
+  case tok::greatergreater:
+  case tok::ellipsis:
+    return true;
+
+  default:
+    return false;
+  }
+}
+
 /// ParseTemplateParameter - Parse a template-parameter (C++ [temp.param]).
 ///
 ///       template-parameter: [C++ temp.param]
@@ -348,12 +382,8 @@ Parser::ParseTemplateParameterList(unsigned Depth,
 ///         'template' '<' template-parameter-list '>' 'class' identifier[opt] = id-expression
 Parser::DeclPtrTy
 Parser::ParseTemplateParameter(unsigned Depth, unsigned Position) {
-  if (Tok.is(tok::kw_class) ||
-      (Tok.is(tok::kw_typename) &&
-       // FIXME: Next token has not been annotated!
-       NextToken().isNot(tok::annot_typename))) {
+  if (isStartOfTemplateTypeParameter())
     return ParseTypeParameter(Depth, Position);
-  }
 
   if (Tok.is(tok::kw_template))
     return ParseTemplateTemplateParameter(Depth, Position);
diff --git a/test/CXX/temp/temp.param/p2.cpp b/test/CXX/temp/temp.param/p2.cpp
index a402cf6f88..d40f99b58a 100644
--- a/test/CXX/temp/temp.param/p2.cpp
+++ b/test/CXX/temp/temp.param/p2.cpp
@@ -8,7 +8,8 @@ template<typename T> struct X;
 
 // typename followed by aqualified-id denotes the type in a non-type
 // parameter-declaration.
-// FIXME: template<typename T, typename T::type Value> struct Y;
+template<typename T, typename T::type Value> struct Y0;
+template<typename T, typename X<T>::type Value> struct Y1;
 
 // A storage class shall not be specified in a template-parameter declaration.
 template<static int Value> struct Z; // FIXME: expect an error
-- 
2.40.0