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Look at arguments when generating constraints for an overload #8845

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Merged
msullivan merged 1 commit into from
May 19, 2020
Merged

Look at arguments when generating constraints for an overload #8845

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5 changes: 2 additions & 3 deletions mypy/constraints.py
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Original file line number Diff line number Diff line change
Expand Up @@ -486,12 +486,11 @@ def infer_against_overloaded(self, overloaded: Overloaded,
template: CallableType) -> List[Constraint]:
# Create constraints by matching an overloaded type against a template.
# This is tricky to do in general. We cheat by only matching against
# the first overload item, and by only matching the return type. This
# the first overload item that is callable compatible. This

@ilevkivskyi ilevkivskyi May 19, 2020

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This comment is 8 years old. I think this answers your question in the PR description.

# seems to work somewhat well, but we should really use a more
# reliable technique.
item = find_matching_overload_item(overloaded, template)
return infer_constraints(template.ret_type, item.ret_type,
self.direction)
return infer_constraints(template, item, self.direction)

def visit_tuple_type(self, template: TupleType) -> List[Constraint]:
actual = self.actual
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25 changes: 25 additions & 0 deletions test-data/unit/check-overloading.test
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Expand Up @@ -5099,3 +5099,28 @@ def foo(x: MyInt) -> int: ...
def foo(x):
...
[builtins fixtures/tuple.pyi]

[case testOverloadedToGeneric]
from typing import TypeVar, Callable, NewType, overload, Union

# int in our stubs isn't overloaded
class fakeint:
@overload
def __init__(self, x: Union[str, bytes] = ...) -> None: ...
@overload
def __init__(self, x: Union[str, bytes], base: int) -> None: ...
def __init__(self, *args) -> None: pass # type: ignore


U = TypeVar('U')
V = TypeVar('V')
W = TypeVar('W')
def compose(f: Callable[[U], V], g: Callable[[W], U]) -> Callable[[W], V]:
return lambda x: f(g(x))

ID = NewType("ID", fakeint)

compose(ID, fakeint)("test")
reveal_type(compose(ID, fakeint)) # N: Revealed type is 'def (Union[builtins.str, builtins.bytes]) -> __main__.ID*'

[builtins fixtures/tuple.pyi]