Update token.cpp

Author: chrchr-github

lib/token.cpp

@@ -2433,6 +2433,7 @@ std::pair<const Token*, const Token*> Token::typeDecl(const Token* tok, bool poi
                     varTok = varTok->next();
                 while (Token::Match(varTok, "%name% ::"))
                     varTok = varTok->tokAt(2);
+                assert(varTok != tok);
                 std::pair<const Token*, const Token*> r = typeDecl(varTok);
                 if (r.first)
                     return r;