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Get type information from isinstance assertions #1346

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Merged
gvanrossum merged 2 commits into from
Apr 8, 2016
Merged

Get type information from isinstance assertions #1346

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e14ee0b
Get type information from isinstance assertions
ddfisher Apr 8, 2016
710dce0
Add test
ddfisher Apr 8, 2016
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10 changes: 10 additions & 0 deletions mypy/checker.py
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Original file line number Diff line number Diff line change
Expand Up @@ -1709,6 +1709,16 @@ def visit_operator_assignment_stmt(self,
def visit_assert_stmt(self, s: AssertStmt) -> Type:
self.accept(s.expr)

# If this is asserting some isinstance check, bind that type in the following code
true_map, _ = find_isinstance_check(
s.expr, self.type_map,
self.typing_mode_weak()
)

if true_map:
for var, type in true_map.items():
self.binder.push(var, type)

def visit_raise_stmt(self, s: RaiseStmt) -> Type:
"""Type check a raise statement."""
self.breaking_out = True
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7 changes: 7 additions & 0 deletions mypy/test/data/check-isinstance.test
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Expand Up @@ -817,3 +817,10 @@ def f(x: Union[A, B]) -> None:
if not isinstance(x, B):
f(x)
[builtins fixtures/isinstance.py]

[case testAssertIsinstance]
def f(x: object):
assert isinstance(x, int)
y = 0 # type: int
y = x
[builtins fixtures/isinstance.py]