8000 Polymorphic inference: support for parameter specifications and lambdas by ilevkivskyi · Pull Request #15837 · python/mypy · GitHub
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Polymorphic inference: support for parameter specifications and lambdas #15837

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Merged
merged 15 commits into from
Aug 15, 2023
Merged

Polymorphic inference: support for parameter specifications and lambdas #15837

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9b4eac8
Add basic support for polymorphic infernce with ParamSpec
Aug 7, 2023
1959136
Some ParamSpec cleanup
Aug 8, 2023
e796c6a
Add pop-off/on tests plus small fix
Aug 8, 2023
177b312
Some more ParamSpec cleanup
Aug 8, 2023
420f60d
More tests and fixes
Aug 8, 2023
d7cfbe9
Support lambdas
Aug 9, 2023
d4c9146
Fix and support Concatenate
Aug 9, 2023
0af630f
Fix accidental TypeVar id clash
Aug 9, 2023
c5c1b76
Some cleanups
Aug 9, 2023
582a4de
Fix urllib crash; some assert tweak
Aug 9, 2023
4f8afce
Address CR
Aug 10, 2023
2d21032
Couple fixes
Aug 10, 2023
59963c4
Fix overload issue
Aug 10, 2023
72da8f5
Fix corner case with upper bounds
Aug 11, 2023
7a87692
Postpone few unneeded hacky changes; re-organize TODOs
Aug 11, 2023
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Fix urllib crash; some assert tweak
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Ivan Levkivskyi committed Aug 9, 2023
commit 582a4deafd0a4c64ac6a53eb648b9f73502fc28b
10 changes: 7 additions & 3 deletions mypy/applytype.py
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Original file line number Diff line number Diff line change
Expand Up @@ -9,7 +9,6 @@
AnyType,
CallableType,
Instance,
Parameters,
ParamSpecType,
PartialType,
TupleType,
Expand Down Expand Up @@ -109,8 +108,13 @@ def apply_generic_arguments(
if param_spec is not None:
nt = id_to_type.get(param_spec.id)
if nt is not None:
if isinstance(nt, Parameters):
callable = callable.expand_param_spec(nt)
# ParamSpec expansion is special-cased, so we need to always expand callable
# as a whole, not expanding arguments individually.
callable = expand_type(callable, id_to_type)
assert isinstance(callable, CallableType)
return callable.copy_modified(
variables=[tv for tv in tvars if tv.id not in id_to_type]
)

# Apply arguments to argument types.
var_arg = callable.var_arg()
Expand Down
2 changes: 1 addition & 1 deletion mypy/types.py
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Expand Up @@ -1577,7 +1577,7 @@ def __init__(
self.arg_kinds = arg_kinds
self.arg_names = list(arg_names)
assert len(arg_types) == len(arg_kinds) == len(arg_names)
assert not any(isinstance(t, (Parameters, ParamSpecType)) for t in arg_types)
assert not any(isinstance(t, Parameters) for t in arg_types)
self.min_args = arg_kinds.count(ARG_POS)
self.is_ellipsis_args = is_ellipsis_args
self.variables = variables or []
Expand Down
13 changes: 13 additions & 0 deletions test-data/unit/check-parameter-specification.test
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Expand Up @@ -1555,3 +1555,16 @@ def test(x: U) -> U: ...
reveal_type(dec) # N: Revealed type is "def [P, T] (f: def (*P.args, **P.kwargs) -> T`-2) -> def (*P.args, **P.kwargs) -> builtins.list[T`-2]"
reveal_type(dec(test)) # N: Revealed type is "def [T] (x: T`2) -> builtins.list[T`2]"
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Could you add a bit kinda like this?:

class A: ...
TA = TypeVar("T", bound=A)

def test_with_bound(x: TA) -> TA: ...
reveal_type(dec(test_with_bound))
dec(test_with_bound)(0)  # should error
dec(test_with_bound)(A())  # should be AOK

? I'm a bit concerned about the replacing of type variables here, though I do remember seeing something in an earlier PR about updating bounds so that's probably already handled.

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Yes, upper bounds should be ~decently handled. I added the test.

[builtins fixtures/paramspec.pyi]

[case testParamSpecNestedApplyNoCrash]
from typing import Callable, TypeVar
from typing_extensions import ParamSpec

P = ParamSpec("P")
T = TypeVar("T")

def apply(fn: Callable[P, T], *args: P.args, **kwargs: P.kwargs) -> T: ...
def test() -> None: ...
# TODO: avoid this error, although it may be non-trivial.
apply(apply, test) # E: Argument 2 to "apply" has incompatible type "Callable[[], None]"; expected "Callable[P, T]"
[builtins fixtures/paramspec.pyi]
0