[mgaunard]

You don't need to know the whole codebase to understand a piece of code, just what the declarations of the names being referenced in that piece of code are (in C++, a name may be a macro, a type, a template, a variable or a function, and depending on which kind, may have all kinds of other properties attached).

Yes, you need to look at the declarations of names to know what the resulting type of expressions involving those names is. I don't see that as being surprising or unusual. The same is also true in C.