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Treat varargs as legal context in default lambda argument #2770

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Merged
merged 1 commit into from
Feb 1, 2017
Merged

Treat varargs as legal context in default lambda argument #2770

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2 changes: 1 addition & 1 deletion mypy/checkexpr.py
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Original file line number Diff line number Diff line change
Expand Up @@ -1799,7 +1799,7 @@ def infer_lambda_type_using_context(self, e: FuncExpr) -> Optional[CallableType]

if ARG_STAR in arg_kinds or ARG_STAR2 in arg_kinds:
# TODO treat this case appropriately
return None
return callable_ctx
if callable_ctx.arg_kinds != arg_kinds:
# Incompatible context; cannot use it to infer types.
self.chk.fail(messages.CANNOT_INFER_LAMBDA_TYPE, e)
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11 changes: 11 additions & 0 deletions test-data/unit/check-inference.test
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Expand Up @@ -1033,7 +1033,18 @@ b = lambda: None # type: Callable[[], None]
f(b)
g(b) # E: Argument 1 to "g" has incompatible type Callable[[], None]; expected Callable[[], int]

[case testLambdaDefaultContext]
# flags: --strict-optional
from typing import Callable
def f(a: Callable[..., None] = lambda *a, **k: None):
pass

def g(a: Callable[..., None] = lambda *a, **k: 1): # E: Incompatible return value type (got "int", expected None)
pass
[out]
main:6: error: Incompatible types in assignment (expression has type Callable[[StarArg(Any), KwArg(Any)], int], variable has type Callable[..., None])

[builtins fixtures/dict.pyi]
-- Boolean operators
-- -----------------

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