It doesn't need feedback from the type-checker. The type is not required, only whether a symbol is a type symbol. So it is enough to have feedback from the lexi

It doesn't need feedback from the type-checker. The type is not required, only whether a symbol is a type symbol. So it is enough to have feedback from the lexical scope, which can be tracked during parsing without any type analysis. It's a compromise, but a useful and simple one. C has been doing it since the 70s ("typedef").