Implement C++0x [lex.pptoken]p3's handling of <::.

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@129525 91177308-0d34-0410-b5e6-96231b3b80d8

lib/Lex/Lexer.cpp

@@ -2398,6 +2398,21 @@ LexNextToken:
       CurPtr = ConsumeChar(CurPtr, SizeTmp, Result);
       Kind = tok::lessequal;
     } else if (Features.Digraphs && Char == ':') {     // '<:' -> '['
+      if (Features.CPlusPlus0x &&
+          getCharAndSize(CurPtr + SizeTmp, SizeTmp2) == ':') {
+        // C++0x [lex.pptoken]p3:
+        //  Otherwise, if the next three characters are <:: and the subsequent
+        //  character is neither : nor >, the < is treated as a preprocessor
+        //  token by itself and not as the first character of the alternative
+        //  token <:.
+        unsigned SizeTmp3;
+        char After = getCharAndSize(CurPtr + SizeTmp + SizeTmp2, SizeTmp3);
+        if (After != ':' && After != '>') {
+          Kind = tok::less;
+          break;
+        }
+      }
+
       CurPtr = ConsumeChar(CurPtr, SizeTmp, Result);
       Kind = tok::l_square;
     } else if (Features.Digraphs && Char == '%') {     // '<%' -> '{'

test/CXX/lex/lex.pptoken/p3-0x.cpp

@@ -0,0 +1,11 @@
+// RUN: %clang_cc1 -fsyntax-only -std=c++0x -verify %s
+
+int a<::> = { 1, 2, 3 };
+int b = a<:::a<:0:>:>;
+bool c = a<:0:><::b;
+
+template<int &n> void f() {}
+template void f<::b>();
+
+#define x a<:: ## : b :>
+int d = x; // expected-error {{pasting formed ':::', an invalid preprocessing token}} expected-error {{expected unqualified-id}}