mirrors/cpython
1
0
Fork 0
mirror of https://github.com/python/cpython.git synced 2025-11-25 04:34:37 +00:00
Code Issues Projects Releases Packages Wiki Activity Actions 11

gh-90633: Improve error and docs for typing.assert_never (#91720)

Browse source 
Closes #90633

Co-authored-by: Alex Waygood <Alex.Waygood@Gmail.com>
This commit is contained in:
Jelle Zijlstra 2022-04-25 06:40:18 -07:00 • committed by GitHub
parent 9ff2f12c87
commit 93d280141c
No known key found for this signature in database
GPG key ID: 4AEE18F83AFDEB23
4 changed files with 37 additions and 2 deletions
Download patch file Download diff file Expand all files Collapse all files

8
Lib/typing.py
View file

@ -2382,6 +2382,9 @@ def is_typeddict(tp):
return isinstance(tp, _TypedDictMeta)
_ASSERT_NEVER_REPR_MAX_LENGTH = 100
def assert_never(arg: Never, /) -> Never:
"""Statically assert that a line of code is unreachable.
@ -2402,7 +2405,10 @@ def assert_never(arg: Never, /) -> Never:
At runtime, this throws an exception when called.
"""
raise AssertionError("Expected code to be unreachable")
value = repr(arg)
if len(value) > _ASSERT_NEVER_REPR_MAX_LENGTH:
value = value[:_ASSERT_NEVER_REPR_MAX_LENGTH] + '...'
raise AssertionError(f"Expected code to be unreachable, but got: {value}")
def no_type_check(arg):