I don't think what you've said is precisely true...
a b(c x);
can be syntactically correct even if c is not a type. Trivially, any of the four tokens could be preprocessor definitions. Even if we are talking about preprocessed c++, the following statement is syntactically correct:
Preprocessor tokens: by that logic, just about anything is syntactically correct. I'd prefer to deal with the syntax of a program after the preprocessor is done with it.
Using "new": Yes, that's right. OTOH, if "c" is literally "c", and not a placeholder for something else, then it looks like my statement is correct. More generally, let c be a placeholder for any identifier, and my statement is correct.[1]
