C++: Fix crash when deducing auto (with invalid ids)

Task-number: QTCREATORBUG-7801

Change-Id: I61436148ed1428a50a6840ba9109310a57dabaa4
Reviewed-by: Roberto Raggi <roberto.raggi@nokia.com>

src/libs/cplusplus/ResolveExpression.h

@@ -36,6 +36,7 @@
 #include <ASTVisitor.h>
 #include <FullySpecifiedType.h>
 #include <Bind.h>
+#include <set>
 
 namespace CPlusPlus {
 
@@ -118,12 +119,20 @@ protected:
     // Objective-C expressions
     virtual bool visit(ObjCMessageExpressionAST *ast);
 
+
 private:
+    struct IdentifierComp
+    {
+        bool operator()(const Identifier *a, const Identifier *b) const
+        { return strcmp(a->chars(), b->chars()) < 0; }
+    };
+
     Scope *_scope;
     LookupContext _context;
     Bind bind;
     QList<LookupItem> _results;
     bool _reference;
+    std::set<const Identifier *, IdentifierComp> _blockedIds; // Replace by a hash impl.
 };
 
 } // namespace CPlusPlus