1 files changed, 38 insertions, 14 deletions

diff --git a/clang/lib/Parse/ParseTentative.cpp b/clang/lib/Parse/ParseTentative.cpp
index 4393326f6c7..e97a8e5b544 100644
--- a/clang/lib/Parse/ParseTentative.cpp
+++ b/clang/lib/Parse/ParseTentative.cpp
@@ -653,12 +653,15 @@ Parser::isCXX11AttributeSpecifier(bool Disambiguate,
   if (!Disambiguate && !getLangOpts().ObjC)
     return CAK_AttributeSpecifier;
 
+  // '[[using ns: ...]]' is an attribute.
+  if (GetLookAheadToken(2).is(tok::kw_using))
+    return CAK_AttributeSpecifier;
+
   RevertingTentativeParsingAction PA(*this);
 
   // Opening brackets were checked for above.
   ConsumeBracket();
 
-  // Outside Obj-C++11, treat anything with a matching ']]' as an attribute.
   if (!getLangOpts().ObjC) {
     ConsumeBracket();
 
@@ -677,24 +680,45 @@ Parser::isCXX11AttributeSpecifier(bool Disambiguate,
   //   4) [[obj]{ return self; }() doStuff]; Lambda in message send.
   // (1) is an attribute, (2) is ill-formed, and (3) and (4) are accepted.
 
-  // If we have a lambda-introducer, then this is definitely not a message send.
+  // Check to see if this is a lambda-expression.
   // FIXME: If this disambiguation is too slow, fold the tentative lambda parse
   // into the tentative attribute parse below.
-  LambdaIntroducer Intro;
-  if (!TryParseLambdaIntroducer(Intro)) {
-    // A lambda cannot end with ']]', and an attribute must.
-    bool IsAttribute = Tok.is(tok::r_square);
-
-    if (IsAttribute)
-      // Case 1: C++11 attribute.
-      return CAK_AttributeSpecifier;
+  {
+    RevertingTentativeParsingAction LambdaTPA(*this);
+    LambdaIntroducer Intro;
+    LambdaIntroducerTentativeParse Tentative;
+    if (ParseLambdaIntroducer(Intro, &Tentative)) {
+      // We hit a hard error after deciding this was not an attribute.
+      // FIXME: Don't parse and annotate expressions when disambiguating
+      // against an attribute.
+      return CAK_NotAttributeSpecifier;
+    }
 
-    if (OuterMightBeMessageSend)
-      // Case 4: Lambda in message send.
+    switch (Tentative) {
+    case LambdaIntroducerTentativeParse::MessageSend:
+      // Case 3: The inner construct is definitely a message send, so the
+      // outer construct is definitely not an attribute.
       return CAK_NotAttributeSpecifier;
 
-    // Case 2: Lambda in array size / index.
-    return CAK_InvalidAttributeSpecifier;
+    case LambdaIntroducerTentativeParse::Success:
+    case LambdaIntroducerTentativeParse::Incomplete:
+      // This is a lambda-introducer or attribute-specifier.
+      if (Tok.is(tok::r_square))
+        // Case 1: C++11 attribute.
+        return CAK_AttributeSpecifier;
+
+      if (OuterMightBeMessageSend)
+        // Case 4: Lambda in message send.
+        return CAK_NotAttributeSpecifier;
+
+      // Case 2: Lambda in array size / index.
+      return CAK_InvalidAttributeSpecifier;
+
+    case LambdaIntroducerTentativeParse::Invalid:
+      // No idea what this is; we couldn't parse it as a lambda-introducer.
+      // Might still be an attribute-specifier or a message send.
+      break;
+    }
   }
 
   ConsumeBracket();