They could. This is the way most early implementations of templates worked, and is still the way the Microsoft compiler worked. It was felt (in the committee) that this was too error prone; it made it too easy to accidentally hijack a name, with the instantiation in one translation unit picking up a local name, … Read more
Both compilers are correct. From [temp.res]/8: If no valid specialization can be generated for a template, and that template is not instantiated, the template is ill-formed, no diagnostic required. There does not exist a valid specialization that can be generated from the primary template Hitchhiker, so it is ill-formed, no diagnostic required. clang chooses to … Read more
(See here also for my C++11 answer) In order to parse a C++ program, the compiler needs to know whether certain names are types or not. The following example demonstrates that: t * f; How should this be parsed? For many languages a compiler doesn’t need to know the meaning of a name in order … Read more