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rwbartonJukkaL
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Use isinstance information when type checking 'or' expressions (#1709)
Note: This is not the same as #942. It does address a pattern which occurs at least once in mypy itself though: ``` if res and (not isinstance(res, Instance) or cast(Instance, res).args): ```
1 parent 9cd1954 commit feaabde

2 files changed

Lines changed: 14 additions & 5 deletions

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‎mypy/checkexpr.py‎

Lines changed: 8 additions & 5 deletions
Original file line numberDiff line numberDiff line change
@@ -1080,16 +1080,19 @@ def check_boolean_op(self, e: OpExpr, context: Context) -> Type:
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left_type = self.accept(e.left, ctx)
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if e.op == 'and':
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# else_map unused
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if_map, else_map = \
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right_map, _ = \
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mypy.checker.find_isinstance_check(e.left, self.chk.type_map,
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self.chk.typing_mode_weak())
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elif e.op == 'or':
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_, right_map = \
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mypy.checker.find_isinstance_check(e.left, self.chk.type_map,
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self.chk.typing_mode_weak())
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else:
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if_map = None
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right_map = None
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self.chk.binder.push_frame()
1091-
if if_map:
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for var, type in if_map.items():
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if right_map:
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for var, type in right_map.items():
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self.chk.binder.push(var, type)
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right_type = self.accept(e.right, left_type)

‎test-data/unit/check-isinstance.test‎

Lines changed: 6 additions & 0 deletions
Original file line numberDiff line numberDiff line change
@@ -731,6 +731,12 @@ x = B() # type: A
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if isinstance(x, B) and x.flag:
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pass
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if isinstance(x, B) or x.flag: # E: "A" has no attribute "flag"
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pass
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if not isinstance(x, B) or x.flag:
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pass
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if not isinstance(x, B) and x.flag: # E: "A" has no attribute "flag"
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pass
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[builtins fixtures/isinstancelist.py]
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[case testIsinstanceExpression]
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class A:

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