From f3ac415f93fd4abedef31c7e36ea5dd4f8ae387b Mon Sep 17 00:00:00 2001 From: Vincent Barbaresi Date: Sat, 10 Oct 2020 14:27:23 +0200 Subject: [PATCH] disable unreachable warnings in boolean ops on TypeVars with value restriction This paragraph explains the limitation with TypeVars: https://github.com/python/mypy/blob/eb50379defc13cea9a8cbbdc0254a578ef6c415e/mypy/checker.py#L967-#L974 We currently have no way of checking for all the type expansions, and it's causing the issue https://github.com/python/mypy/issues/9456 Using `self.chk.should_report_unreachable_issues()` honors the suppression of the unreachable warning for TypeVar with value restrictions --- mypy/checkexpr.py | 2 +- test-data/unit/check-unreachable-code.test | 14 ++++++++++++++ 2 files changed, 15 insertions(+), 1 deletion(-) diff --git a/mypy/checkexpr.py b/mypy/checkexpr.py index 9c0e2f4048b3..758d219cfd98 100644 --- a/mypy/checkexpr.py +++ b/mypy/checkexpr.py @@ -2762,7 +2762,7 @@ def check_boolean_op(self, e: OpExpr, context: Context) -> Type: # the analysis from the semanal phase below. We assume that nodes # marked as unreachable during semantic analysis were done so intentionally. # So, we shouldn't report an error. - if self.chk.options.warn_unreachable: + if self.chk.should_report_unreachable_issues(): if right_map is None: self.msg.unreachable_right_operand(e.op, e.right) diff --git a/test-data/unit/check-unreachable-code.test b/test-data/unit/check-unreachable-code.test index f5b49d87289a..e95faf503d99 100644 --- a/test-data/unit/check-unreachable-code.test +++ b/test-data/unit/check-unreachable-code.test @@ -925,6 +925,7 @@ from typing import TypeVar, Generic T1 = TypeVar('T1', bound=int) T2 = TypeVar('T2', int, str) +T3 = TypeVar('T3', None, str) def test1(x: T1) -> T1: if isinstance(x, int): @@ -961,6 +962,19 @@ class Test3(Generic[T2]): # Same issue as above reveal_type(self.x) + +class Test4(Generic[T3]): + def __init__(self, x: T3): + # https://github.com/python/mypy/issues/9456 + # On TypeVars with value restrictions, we currently have no way + # of checking a statement for all the type expansions. + # Thus unreachable warnings are disabled + if x and False: + pass + # This test should fail after this limitation is removed. + if False and x: + pass + [builtins fixtures/isinstancelist.pyi] [case testUnreachableFlagContextManagersNoSuppress] pFad - Phonifier reborn

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