8000 Fix #1081. When comparing template to actual arg types, stop at shortest. by gvanrossum · Pull Request #1085 · python/mypy · GitHub
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Fix #1081. When comparing template to actual arg types, stop at shortest. #1085

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Fix #1081. When comparing template to actual arg types, stop at shortest. #1085

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7 changes: 3 additions & 4 deletions mypy/constraints.py
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Original file line number Diff line number Diff line change
Expand Up @@ -225,11 +225,10 @@ def visit_callable_type(self, template: CallableType) -> List[Constraint]:
# We can't infer constraints from arguments if the template is Callable[..., T] (with
# literal '...').
if not template.is_ellipsis_args:
for i in range(len(template.arg_types)):
# The lengths should match, but don't crash (it will error elsewhere).
for t, a in zip(template.arg_types, cactual.arg_types):
# Negate constraints due function argument type contravariance.
res.extend(negate_constraints(infer_constraints(
template.arg_types[i], cactual.arg_types[i],
self.direction)))
res.extend(negate_constraints(infer_constraints(t, a, self.direction)))
res.extend(infer_constraints(template.ret_type, cactual.ret_type,
self.direction))
return res
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9 changes: 9 additions & 0 deletions mypy/test/data/check-functions.test
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Expand Up @@ -178,6 +178,15 @@ def f(x: B) -> B: pass
@overload
def f(x: C) -> C: pass

[case testInferConstraintsUnequalLengths]
from typing import Any, Callable, List
def f(fields: List[Callable[[Any], Any]]): pass
class C: pass
f([C]) # E: List item 0 has incompatible type
class D:
def __init__(self, a, b): pass
f([D]) # E: List item 0 has incompatible type
[builtins fixtures/list.py]

-- Default argument values
-- -----------------------
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0