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Improve error message for an invalid callable type #4213

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Merged
merged 1 commit into from
Nov 15, 2017
Merged

Improve error message for an invalid callable type #4213

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2 changes: 1 addition & 1 deletion mypy/typeanal.py
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Original file line number Diff line number Diff line change
Expand Up @@ -467,7 +467,7 @@ def analyze_callable_type(self, t: UnboundType) -> Type:
self.fail('The first argument to Callable must be a list of types or "..."', t)
return AnyType(TypeOfAny.from_error)
else:
self.fail('Invalid function type', t)
self.fail('Please use "Callable[[<parameters>], <return type>]" or "Callable"', t)
return AnyType(TypeOfAny.from_error)
assert isinstance(ret, CallableType)
return ret.accept(self)
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2 changes: 1 addition & 1 deletion test-data/unit/check-generics.test
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Expand Up @@ -812,7 +812,7 @@ class Node(Generic[T]):
def __init__(self, x: T) -> None:
...

BadC = Callable[T] # E: Invalid function type
BadC = Callable[T] # E: Please use "Callable[[<parameters>], <return type>]" or "Callable"

C = Callable[..., T]
C2 = Callable[[T, T], Node[T]]
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4 changes: 2 additions & 2 deletions test-data/unit/semanal-errors.test
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Expand Up @@ -819,8 +819,8 @@ y = None # type: Callable[int]
z = None # type: Callable[int, int, int]
[out]
main:2: error: The first argument to Callable must be a list of types or "..."
main:3: error: Invalid function type
main:4: error: Invalid function type
main:3: error: Please use "Callable[[<parameters>], <return type>]" or "Callable"
main:4: error: Please use "Callable[[<parameters>], <return type>]" or "Callable"

[case testAbstractGlobalFunction]
import typing
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