Difference between errors "does not name a type" and "has not been declared"

Question

After a codebase I am working on has been converted automatically from Java to C++ (Yes, yes, I know, not a good idea, but long story made short, it was needed), I have found that in many classes I have the two following errors, related to my ClassNameXXX type:

‘ClassNameXXX’ does not name a type

and

‘ClassNameXXX’ has not been declared

I understand that the casue of the problem is a matter of cyclic inclusions between the ClassNameXXX.h header and others (and I am working hard to resolve that) but I was wondering what is the actual difference between the two error messages (Maybe this would give me some clues for the resolution of the cycles).

Thanks in advance!

Answer 1

'ClassNameXXX' has not been declared

This one, as the name suggests, emited when you are trying to define something that has not been declared, for example if you write void SomeClass::foo(){} without declaring SomeClass first (eg you forgot to #include someClass.h in someClass.cpp). The compiler understands that you are trying to define a member of SomeClass , but fails to find it, and gives you the error.

'ClassNameXXX' does not name a type

This one rises in different circumstances, eg

class MyClassOne
{
    MyClassTwo _member;//error
};

class MyClassTwo
{
};

Here the compiler understands that MyClassTwo is supposed to be the type of _member , but since MyClassTwo is not yet defined at that place, the compiler has no idea that such a type exists, so it tells you that MyClassTwo does not name a type.