C++: Fix crash in auto deducing mechanism

There was an inconsistency, since the AST used in ResolveExpression
was not really the same previously computed. In the particular issue
below a crash could occur, for example, when using auto in a for
range loop.

Task-number: QTCREATORBUG-7828
Change-Id: I02958f434c3cf3b50609546003fc141674ee78d5
Reviewed-by: Eike Ziller <eike.ziller@nokia.com>

src/libs/cplusplus/ResolveExpression.cpp

@@ -460,6 +460,48 @@ bool ResolveExpression::visit(QualifiedNameAST *ast)
     return false;
 }
 
+namespace {
+
+class DeduceAutoCheck : public ASTVisitor
+{
+public:
+    DeduceAutoCheck(const Identifier *id, TranslationUnit *tu)
+        : ASTVisitor(tu), _id(id), _block(false)
+    {
+        accept(tu->ast());
+    }
+
+    virtual bool preVisit(AST *)
+    {
+        if (_block)
+            return false;
+
+        return true;
+    }
+
+    virtual bool visit(SimpleNameAST *ast)
+    {
+        if (ast->name
+                && ast->name->identifier()
+                && strcmp(ast->name->identifier()->chars(), _id->chars()) == 0) {
+            _block = true;
+        }
+
+        return false;
+    }
+
+    virtual bool visit(MemberAccessAST *ast)
+    {
+        accept(ast->base_expression);
+        return false;
+    }
+
+    const Identifier *_id;
+    bool _block;
+};
+
+} // namespace anonymous
+
 bool ResolveExpression::visit(SimpleNameAST *ast)
 {
     QList<LookupItem> candidates = _context.lookup(ast->name, _scope);
@@ -473,8 +515,7 @@ bool ResolveExpression::visit(SimpleNameAST *ast)
         if (item.declaration() == 0)
             continue;
 
-        if (item.type().isAuto()
-                && _blockedIds.find(ast->name->identifier()) == _blockedIds.end()) {
+        if (item.type().isAuto()) {
             const Declaration *decl = item.declaration()->asDeclaration();
             if (!decl)
                 continue;
@@ -498,13 +539,13 @@ bool ResolveExpression::visit(SimpleNameAST *ast)
             Document::Ptr exprDoc =
                     documentForExpression(exprTyper.preprocessedExpression(initializer));
             exprDoc->check();
-            ExpressionAST *exprAST = extractExpressionAST(exprDoc);
-            if (!exprAST)
+
+            DeduceAutoCheck deduceAuto(ast->name->identifier(), exprDoc->translationUnit());
+            if (deduceAuto._block)
                 continue;
 
-            _blockedIds.insert(ast->name->identifier());
-            const QList<LookupItem> &typeItems = resolve(exprAST, decl->enclosingScope());
-            _blockedIds.erase(ast->name->identifier());
+            const QList<LookupItem> &typeItems =
+                    exprTyper(extractExpressionAST(exprDoc), exprDoc, decl->enclosingScope());
             if (typeItems.empty())
                 continue;
 

src/libs/cplusplus/ResolveExpression.h

@@ -121,18 +121,11 @@ protected:
 
 
 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