[PATCH] Parser: support Microsoft syntax for 'typename typedef'

[David Majnemer]

Hi rsmith,

Transform the token sequence for:
typename typedef T U;

to:
typename T typedef U;

Raise a diagnostic when this happens but only if we succeeded handling
the typename.

http://llvm-reviews.chandlerc.com/D1433

Files:
  lib/Parse/Parser.cpp
  test/Parser/MicrosoftExtensions.cpp

Index: lib/Parse/Parser.cpp
===================================================================
--- lib/Parse/Parser.cpp
+++ lib/Parse/Parser.cpp
@@ -1479,7 +1479,28 @@
           || Tok.is(tok::kw_decltype) || Tok.is(tok::annot_template_id))
           && "Cannot be a type or scope token!");
 
-  if (Tok.is(tok::kw_typename)) {
+  if (Tok.is(tok::kw_typename)) {;
+    // MSVC lets you do stuff like:
+    //   typename typedef T_::D D;
+    //
+    // We will consume the typedef token here and put it back after we have
+    // lexed the first identifier, transforming it into something more like:
+    //   typename T_::D typedef D;
+    if (getLangOpts().MicrosoftExt && NextToken().is(tok::kw_typedef)) {
+      Token TypenameToken = Tok;
+      ConsumeToken();
+      Token TypedefToken = Tok;
+      ConsumeToken();
+      PP.EnterToken(Tok);
+      Tok = TypenameToken;
+      bool Result = TryAnnotateTypeOrScopeToken(EnteringContext, NeedType);
+      PP.EnterToken(Tok);
+      Tok = TypedefToken;
+      if (!Result)
+        Diag(Tok.getLocation(), diag::warn_expected_qualified_after_typename);
+      return Result;
+    }
+
     // Parse a C++ typename-specifier, e.g., "typename T::type".
     //
     //   typename-specifier:
@@ -1498,7 +1519,7 @@
         // Attempt to recover by skipping the invalid 'typename'
         if (Tok.is(tok::annot_decltype) ||
             (!TryAnnotateTypeOrScopeToken(EnteringContext, NeedType) &&
-            Tok.isAnnotation())) {
+             Tok.isAnnotation())) {
           unsigned DiagID = diag::err_expected_qualified_after_typename;
           // MS compatibility: MSVC permits using known types with typename.
           // e.g. "typedef typename T* pointer_type"
Index: test/Parser/MicrosoftExtensions.cpp
===================================================================
--- test/Parser/MicrosoftExtensions.cpp
+++ test/Parser/MicrosoftExtensions.cpp
@@ -149,7 +149,9 @@
 
 
 
-class AAAA { };
+class AAAA {
+   typedef int D;
+};
 
 template <typename T>
 class SimpleTemplate {};
@@ -171,6 +173,12 @@
    int k = typename var;// expected-error {{expected a qualified name after 'typename'}}
 }
 
+template <typename T>
+struct TypenameWrongPlace {
+  typename typedef T::D D;// expected-warning {{expected a qualified name after 'typename'}}
+};
+
+extern TypenameWrongPlace<AAAA> PR16925;
 
 __interface MicrosoftInterface;
 __interface MicrosoftInterface {
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