A parser with Chumsky. There’s a lexer with logos too, but that’s simple and fast. Chumsy makes you create parsing functions which are chains of other parsing functions, and the types can become insanely long, if you don’t box some of them for erasure.

edit: to elaborate, it’s not that the type name was 80k characters, the type definition itself was, like TypeA<TypeB<TypeC, TypeD>>, TypeB<TypeE, TypeF<TypeG…>>>