mirror of https://github.com/astral-sh/ruff
107 lines
3.4 KiB
Markdown
107 lines
3.4 KiB
Markdown
# Cycles
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## Function signature
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Deferred annotations can result in cycles in resolving a function signature:
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```py
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from __future__ import annotations
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# error: [invalid-type-form]
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def f(x: f):
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pass
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reveal_type(f) # revealed: def f(x: Unknown) -> Unknown
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```
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## Unpacking
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See: <https://github.com/astral-sh/ty/issues/364>
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```py
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class Point:
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def __init__(self, x: int = 0, y: int = 0) -> None:
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self.x = x
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self.y = y
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def replace_with(self, other: "Point") -> None:
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self.x, self.y = other.x, other.y
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p = Point()
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reveal_type(p.x) # revealed: Unknown | int
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reveal_type(p.y) # revealed: Unknown | int
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```
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## Parameter default values
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This is a regression test for <https://github.com/astral-sh/ty/issues/1402>. When a parameter has a
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default value that references the callable itself, we currently prevent infinite recursion by simply
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falling back to `Unknown` for the type of the default value, which does not have any practical
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impact except for the displayed type. We could also consider inferring `Divergent` when we encounter
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too many layers of nesting (instead of just one), but that would require a type traversal which
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could have performance implications. So for now, we mainly make sure not to panic or stack overflow
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for these seeminly rare cases.
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### Functions
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```py
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class C:
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def f(self: "C"):
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def inner_a(positional=self.a):
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return
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self.a = inner_a
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# revealed: def inner_a(positional=Unknown | (def inner_a(positional=Unknown) -> Unknown)) -> Unknown
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reveal_type(inner_a)
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def inner_b(*, kw_only=self.b):
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return
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self.b = inner_b
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# revealed: def inner_b(*, kw_only=Unknown | (def inner_b(*, kw_only=Unknown) -> Unknown)) -> Unknown
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reveal_type(inner_b)
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def inner_c(positional_only=self.c, /):
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return
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self.c = inner_c
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# revealed: def inner_c(positional_only=Unknown | (def inner_c(positional_only=Unknown, /) -> Unknown), /) -> Unknown
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reveal_type(inner_c)
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def inner_d(*, kw_only=self.d):
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return
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self.d = inner_d
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# revealed: def inner_d(*, kw_only=Unknown | (def inner_d(*, kw_only=Unknown) -> Unknown)) -> Unknown
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reveal_type(inner_d)
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```
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We do, however, still check assignability of the default value to the parameter type:
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```py
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class D:
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def f(self: "D"):
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# error: [invalid-parameter-default] "Default value of type `Unknown | (def inner_a(a: int = Unknown | (def inner_a(a: int = Unknown) -> Unknown)) -> Unknown)` is not assignable to annotated parameter type `int`"
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def inner_a(a: int = self.a): ...
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self.a = inner_a
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```
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### Lambdas
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```py
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class C:
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def f(self: "C"):
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self.a = lambda positional=self.a: positional
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self.b = lambda *, kw_only=self.b: kw_only
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self.c = lambda positional_only=self.c, /: positional_only
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self.d = lambda *, kw_only=self.d: kw_only
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# revealed: (positional=Unknown | ((positional=Unknown) -> Unknown)) -> Unknown
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reveal_type(self.a)
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# revealed: (*, kw_only=Unknown | ((*, kw_only=Unknown) -> Unknown)) -> Unknown
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reveal_type(self.b)
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# revealed: (positional_only=Unknown | ((positional_only=Unknown, /) -> Unknown), /) -> Unknown
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reveal_type(self.c)
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# revealed: (*, kw_only=Unknown | ((*, kw_only=Unknown) -> Unknown)) -> Unknown
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reveal_type(self.d)
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```
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