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Handling `Literal` type in annotations. Resolves: #13672 ## Implementation Since Literals are not a fully defined type in typeshed. I used a trick to figure out when a special form is a literal. When we are inferring assignment types I am checking if the type of that assignment was resolved to typing.SpecialForm and the name of the target is `Literal` if that is the case then I am re creating a new instance type and set the known instance field to `KnownInstance:Literal`. **Why not defining a new type?** From this [issue](https://github.com/python/typeshed/issues/6219) I learned that we want to resolve members to SpecialMethod class. So if we create a new instance here we can rely on the member resolving in that already exists. ## Tests https://typing.readthedocs.io/en/latest/spec/literal.html#equivalence-of-two-literals Since the type of the value inside Literal is evaluated as a Literal(LiteralString, LiteralInt, ...) then the equality is only true when types and value are equal. https://typing.readthedocs.io/en/latest/spec/literal.html#legal-and-illegal-parameterizations The illegal parameterizations are mostly implemented I'm currently checking the slice expression and the slice type to make sure it's valid. https://typing.readthedocs.io/en/latest/spec/literal.html#shortening-unions-of-literals --------- Co-authored-by: Carl Meyer <carl@astral.sh> Co-authored-by: Alex Waygood <Alex.Waygood@Gmail.com>
2.2 KiB
2.2 KiB
Literal
https://typing.readthedocs.io/en/latest/spec/literal.html#literals
Parameterization
from typing import Literal
from enum import Enum
mode: Literal["w", "r"]
mode2: Literal["w"] | Literal["r"]
union_var: Literal[Literal[Literal[1, 2, 3], "foo"], 5, None]
a1: Literal[26]
a2: Literal[0x1A]
a3: Literal[-4]
a4: Literal["hello world"]
a5: Literal[b"hello world"]
a6: Literal[True]
a7: Literal[None]
a8: Literal[Literal[1]]
a9: Literal[Literal["w"], Literal["r"], Literal[Literal["w+"]]]
class Color(Enum):
RED = 0
GREEN = 1
BLUE = 2
b1: Literal[Color.RED]
def f():
reveal_type(mode) # revealed: Literal["w", "r"]
reveal_type(mode2) # revealed: Literal["w", "r"]
# TODO: should be revealed: Literal[1, 2, 3, "foo", 5] | None
reveal_type(union_var) # revealed: Literal[1, 2, 3, 5] | Literal["foo"] | None
reveal_type(a1) # revealed: Literal[26]
reveal_type(a2) # revealed: Literal[26]
reveal_type(a3) # revealed: Literal[-4]
reveal_type(a4) # revealed: Literal["hello world"]
reveal_type(a5) # revealed: Literal[b"hello world"]
reveal_type(a6) # revealed: Literal[True]
reveal_type(a7) # revealed: None
reveal_type(a8) # revealed: Literal[1]
reveal_type(a9) # revealed: Literal["w", "r", "w+"]
# TODO: This should be Color.RED
reveal_type(b1) # revealed: Literal[0]
# error: [invalid-literal-parameter]
invalid1: Literal[3 + 4]
# error: [invalid-literal-parameter]
invalid2: Literal[4 + 3j]
# error: [invalid-literal-parameter]
invalid3: Literal[(3, 4)]
invalid4: Literal[
1 + 2, # error: [invalid-literal-parameter]
"foo",
hello, # error: [invalid-literal-parameter]
(1, 2, 3), # error: [invalid-literal-parameter]
]
Detecting Literal outside typing and typing_extensions
Only Literal that is defined in typing and typing_extension modules is detected as the special Literal.
from typing import _SpecialForm
Literal: _SpecialForm
from other import Literal
a1: Literal[26]
def f():
reveal_type(a1) # revealed: @Todo
Detecting typing_extensions.Literal
from typing_extensions import Literal
a1: Literal[26]
def f():
reveal_type(a1) # revealed: Literal[26]