The point of the ‘import a as a’ and ‘from a import b as b’ syntax for
explicit reexport is that it indicates an intention to do something
different from the ordinary ‘import a’ and ‘from a import b’.

That is not the case with ‘import a.b as b’.  Even mypy’s own code
includes ‘import mypy.types as types’, which was not intended to be a
reexport; if it were, it would be written ‘from mypy import types as
types’.

Pyright agrees that ‘import a.b as b’ should not reexport.

Signed-off-by: Anders Kaseorg <andersk@mit.edu>