Refactoring: make the type of fullname str instead of Bogus[str] (#14435)
The type Bogus[X] is treated as Any when the code is compiled with
mypyc, while it's equivalent to X when only type checking. They are
sometimes used when X is not actually the real type of a value, but
changing it to the correct type would be complicated.
Bogus[str] types are pretty awkward, since we are lying to the type
checker and mypyc only sees Any types.
An empty fullname is now represented by "" instead of None, so we no
longer need a Bogus[str] type.
This might break some plugins, so we should document this in release
notes and the relevant issue that tracks plugin incompatibilities.
(Various small optimizations, including this, together netted a 6%
performance improvement in self check.)
mypy
28e5436b - Refactoring: make the type of fullname str instead of Bogus[str] (#14435)
