‘Foo’ does not name a type

From Cppsyntax

The error

 ‘Foo’ does not name a type

is similar to the error

 ‘Foo’ was not declared in this scope

In both cases, the compiler can't find Foo's declaration. This message is more likely to be found when there is a declaration of a variable, as in an include file:

WRONG

blort.h:

 class Blort 
 {
   public:
     Foo aFoo;    // what is Foo?
 };

RIGHT (assuming that foo.h declares Foo properly)

blort.h:

 #include "foo.h"   // yay, a declaration!
 class Blort 
 {
   public:
     Foo aFoo;
 };