Stubgen produces <TypeList ...> instead of [...]

[evhub]

Under mypy 0.560, running stubgen on

import typing

f: typing.Callable[[int, int], int]

produces

# Stubs for prelude (Python 3.6)
#
# NOTE: This dynamically typed stub was automatically generated by stubgen.

import typing

f: typing.Callable[<TypeList int, int>, int]

which is invalid Python syntax. Instead, <TypeList int, int> should be [int, int].

[evhub]

Whoops, closing as a duplicate of #4638.

[evhub]

Reopening since #4638 was closed as a duplicate. This is fixed by PR #4650.