C++: fix digraph parsing for <:: exception.

According to section 2.5 from the standard:
""" If the input stream has been parsed into preprocessing tokens up to
a given character: ... 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 <:. """

Change-Id: Ib9cdac61e3c2243d1bc1d4471a09ae6bd839fdda
Task-number: QTCREATORBUG-13253
Reviewed-by: Nikolai Kosjar <nikolai.kosjar@theqtcompany.com>

1 files changed, 6 insertions, 2 deletions

diff --git a/src/libs/3rdparty/cplusplus/Lexer.cpp b/src/libs/3rdparty/cplusplus/Lexer.cpp
index a508ce3d30..feddf3a5d0 100644
--- a/src/libs/3rdparty/cplusplus/Lexer.cpp
+++ b/src/libs/3rdparty/cplusplus/Lexer.cpp
@@ -610,8 +610,12 @@ void Lexer::scan_helper(Token *tok)
             yyinp();
             tok->f.kind = T_LESS_EQUAL;
         } else if (_yychar == ':') {
-            yyinp();
-            tok->f.kind = T_LBRACKET;
+            if (*(_currentChar+1) != ':' || *(_currentChar+2) == ':' || *(_currentChar+2) == '>') {
+                yyinp();
+                tok->f.kind = T_LBRACKET;
+            } else {
+                tok->f.kind = T_LESS;
+            }
         } else if (_yychar == '%') {
             yyinp();
             tok->f.kind = T_LBRACE;