Fix meet_types for literal and instance

[randolf-scholz]

• Fixes meet_types gives unexpected results when meeting literal and Instance #19560
• Fixes Specify behavior for Literal? types. #19625

New Tests

• JoinSuite.test_mixed_literal_types tests join between Literal? and other types.
• MeetSuite.test_mixed_literal_types tests meet between Literal? and other types
• TypeOpsSuite.test_simplified_union_with_mixed_str_literals2 tests simplified unions containing Literal? types
• SubtypingSuite.test_literal tests subtype checks with Literal? types
• RestrictionSuite: new test suite for testing the restrict_subtype_away method.
• testJoinLiteralInstanceAndEnum tests join between Literal? and StrEnum

[randolf-scholz]

The first operator failure seems like a bug in typeshed to me: python/typeshed#9004

[randolf-scholz]

Hm, the xarray redundant cast looks like this: mypy-playground

from typing import Literal, cast

type PDDatetimeUnitOptions = Literal["s", "ms", "ns"]

time_unit = cast(PDDatetimeUnitOptions, "s")  # [redundant-cast]

Is the current behavior of emitting redundant cast here intentional? It seems formally incorrect, since "s" should be Literal["s"]? and not Literal["s", "ms", "ns"], but maybe this was introduces as a convenience thing?

In comparison, pyright does not issue RedundantCast here, which aligns with my priors. pyright-playground

[randolf-scholz]

Repro for the pyinstrument change:

from typing import TypedDict, Literal

type AsyncMode = Literal["enabled", "disabled", "strict"]

class Options(TypedDict, total=False):
    async_mode: AsyncMode

def test(kwargs: Options, d: dict[Literal["async_mode"], AsyncMode]) -> None:
    reveal_type(kwargs)
    reveal_type(kwargs.get)
    reveal_type(d.get)
    reveal_type(kwargs.get("async_mode", "disabled"))
    # master: AsyncMode
    # feature: "Literal['enabled'] | Literal['strict'] | Literal['disabled']?"

I believe the problem here is not the new union schema ("x"? | "x" --> "x"? rather than "x"; see #19625), but that mypy is too simplistic about kwargs.get.

reveal_type(kwargs.get)
# mypy: Overload
#        def (str) -> object,
#        def (str, default: object) -> object,
#        def [_T] (str, default: _T`1) -> object)"
# pyright: Overload
#        def (k: Literal['async_mode']) -> (AsyncMode | None)
#        def [T] (k: Literal['async_mode'], default: T | AsyncMode) -> (T | AsyncMode)
#        def [T] (k: str) -> (Any | None), (k: str, default: Any | T) -> (Any | T)

Basically, we want here to pick the second signature shown by pyright, and use the minimal solution T=Never, or equivalently an overload of the form

def [T] (k: Literal['async_mode'], default: AsyncMode) -> (AsyncMode)

[github-actions]

Diff from mypy_primer, showing the effect of this PR on open source code:

prefect (https://github.com/PrefectHQ/prefect)
+ src/prefect/task_worker.py:370: error: Argument 1 to "submit" of "Executor" has incompatible type "Callable[[Callable[_P, _T], **_P], _T]"; expected "Callable[[Callable[[Task[P, R], Optional[UUID], Optional[TaskRun], Optional[dict[str, Any]], Union[PrefectFuture[Any], Any, Iterable[Union[PrefectFuture[Any], Any]], None], Literal['state', 'result'], Optional[dict[str, set[RunInput]]], Optional[dict[str, Any]]], Union[R, State[Any], None]], Task[[VarArg(Any), KwArg(Any)], Any], UUID, TaskRun, dict[Any, Any], list[Any], str, Optional[Any]], Union[Any, State[Any], None]]"  [arg-type]

strawberry (https://github.com/strawberry-graphql/strawberry)
- strawberry/codegen/query_codegen.py:476: error: Redundant cast to "Literal['query', 'mutation', 'subscription']"  [redundant-cast]

operator (https://github.com/canonical/operator)
+ ops/model.py:832: error: Unsupported operand types for - ("set[tuple[Literal['tcp', 'udp', 'icmp'], int | None]]" and "set[tuple[str, int] | tuple[Literal['tcp', 'udp', 'icmp'], int | None]]")  [operator]
+ ops/model.py:834: error: Incompatible types in assignment (expression has type "str", variable has type "Literal['tcp', 'udp', 'icmp']")  [assignment]

core (https://github.com/home-assistant/core)
+ homeassistant/data_entry_flow.py:646: error: Unused "type: ignore" comment  [unused-ignore]
+ homeassistant/data_entry_flow.py:651: error: Unused "type: ignore" comment  [unused-ignore]
- homeassistant/components/evohome/storage.py:98: error: Argument 1 to "fromisoformat" of "date" has incompatible type "object"; expected "str"  [arg-type]

discord.py (https://github.com/Rapptz/discord.py)
- discord/scheduled_event.py:139: error: Incompatible types in assignment (expression has type "object", variable has type "str | None")  [assignment]
- discord/scheduled_event.py:145: error: Incompatible types in assignment (expression has type "object", variable has type "str | None")  [assignment]
- discord/scheduled_event.py:146: error: Incompatible types in assignment (expression has type "object", variable has type "int")  [assignment]
- discord/scheduled_event.py:150: error: Argument 1 to "store_user" of "ConnectionState" has incompatible type "object"; expected "User | PartialUser"  [arg-type]
- discord/scheduled_event.py:155: error: No overload variant of "parse_time" matches argument type "object"  [call-overload]
- discord/scheduled_event.py:155: note: Possible overload variants:
- discord/scheduled_event.py:155: note:     def parse_time(timestamp: None) -> None
- discord/scheduled_event.py:155: note:     def parse_time(timestamp: str) -> datetime
- discord/scheduled_event.py:155: note:     def parse_time(timestamp: str | None) -> datetime | None
- discord/scheduled_event.py:159: error: Argument 1 to "_unroll_metadata" of "ScheduledEvent" has incompatible type "object"; expected "EntityMetadata | None"  [arg-type]
- discord/app_commands/models.py:224: error: No overload variant of "int" matches argument type "object"  [call-overload]
- discord/app_commands/models.py:224: note: Possible overload variants:
- discord/app_commands/models.py:224: note:     def __new__(cls, str | Buffer | SupportsInt | SupportsIndex | SupportsTrunc = ..., /) -> int
- discord/app_commands/models.py:224: note:     def __new__(cls, str | bytes | bytearray, /, base: SupportsIndex) -> int
- discord/app_commands/models.py:231: error: Incompatible types in assignment (expression has type "object", variable has type "bool")  [assignment]
- discord/app_commands/models.py:237: error: Argument 1 to "_from_value" of "ArrayFlags" has incompatible type "object"; expected "Sequence[int]"  [arg-type]
- discord/app_commands/models.py:243: error: Argument 1 to "_from_value" of "ArrayFlags" has incompatible type "object"; expected "Sequence[int]"  [arg-type]
- discord/app_commands/models.py:245: error: Incompatible types in assignment (expression has type "object", variable has type "bool")  [assignment]
- discord/app_commands/models.py:246: error: Argument 1 to "_to_locale_dict" has incompatible type "object"; expected "dict[str, str]"  [arg-type]
- discord/app_commands/models.py:247: error: Argument 1 to "_to_locale_dict" has incompatible type "object"; expected "dict[str, str]"  [arg-type]
- discord/app_commands/models.py:1065: error: Argument 1 to "_to_locale_dict" has incompatible type "object"; expected "dict[str, str]"  [arg-type]
- discord/app_commands/models.py:1066: error: Argument 1 to "_to_locale_dict" has incompatible type "object"; expected "dict[str, str]"  [arg-type]
- discord/app_commands/models.py:1164: error: Argument 1 to "_to_locale_dict" has incompatible type "object"; expected "dict[str, str]"  [arg-type]
- discord/app_commands/models.py:1165: error: Argument 1 to "_to_locale_dict" has incompatible type "object"; expected "dict[str, str]"  [arg-type]
- discord/message.py:868: error: "object" has no attribute "items"  [attr-defined]
- discord/app_commands/transformers.py:139: error: Incompatible types in assignment (expression has type "list[dict[str, Any]]", target has type "str | int")  [assignment]
+ discord/app_commands/transformers.py:139: error: Incompatible types in assignment (expression has type "list[dict[str, Any]]", target has type "bool | str | int")  [assignment]
- discord/app_commands/transformers.py:141: error: Incompatible types in assignment (expression has type "list[int]", target has type "str | int")  [assignment]
+ discord/app_commands/transformers.py:141: error: Incompatible types in assignment (expression has type "list[int]", target has type "bool | str | int")  [assignment]
- discord/app_commands/transformers.py:149: error: Incompatible types in assignment (expression has type "int | float", target has type "str | int")  [assignment]
+ discord/app_commands/transformers.py:149: error: Incompatible types in assignment (expression has type "int | float", target has type "bool | str | int")  [assignment]
- discord/app_commands/transformers.py:151: error: Incompatible types in assignment (expression has type "int | float", target has type "str | int")  [assignment]
+ discord/app_commands/transformers.py:151: error: Incompatible types in assignment (expression has type "int | float", target has type "bool | str | int")  [assignment]

dedupe (https://github.com/dedupeio/dedupe)
- dedupe/api.py:1547: error: Redundant cast to "Literal['match', 'distinct']"  [redundant-cast]

AutoSplit (https://github.com/Toufool/AutoSplit)
-   File "/tmp/mypy_primer/mypy_old/venv/bin/mypy", line 7, in <module>
+   File "/tmp/mypy_primer/mypy_new/venv/bin/mypy", line 7, in <module>
-   File "/tmp/mypy_primer/mypy_old/venv/lib/python3.13/site-packages/mypy/__main__.py", line 15, in console_entry
+   File "/tmp/mypy_primer/mypy_new/venv/lib/python3.13/site-packages/mypy/__main__.py", line 15, in console_entry
-   File "/tmp/mypy_primer/mypy_old/venv/lib/python3.13/site-packages/mypy/main.py", line 127, in main
+   File "/tmp/mypy_primer/mypy_new/venv/lib/python3.13/site-packages/mypy/main.py", line 127, in main
-   File "/tmp/mypy_primer/mypy_old/venv/lib/python3.13/site-packages/mypy/main.py", line 211, in run_build
+   File "/tmp/mypy_primer/mypy_new/venv/lib/python3.13/site-packages/mypy/main.py", line 211, in run_build
-   File "/tmp/mypy_primer/mypy_old/venv/lib/python3.13/site-packages/mypy/build.py", line 196, in build
+   File "/tmp/mypy_primer/mypy_new/venv/lib/python3.13/site-packages/mypy/build.py", line 196, in build
-   File "/tmp/mypy_primer/mypy_old/venv/lib/python3.13/site-packages/mypy/build.py", line 272, in _build
+   File "/tmp/mypy_primer/mypy_new/venv/lib/python3.13/site-packages/mypy/build.py", line 272, in _build
-   File "/tmp/mypy_primer/mypy_old/venv/lib/python3.13/site-packages/mypy/build.py", line 2946, in dispatch
+   File "/tmp/mypy_primer/mypy_new/venv/lib/python3.13/site-packages/mypy/build.py", line 2946, in dispatch
-   File "/tmp/mypy_primer/mypy_old/venv/lib/python3.13/site-packages/mypy/build.py", line 3346, in process_graph
+   File "/tmp/mypy_primer/mypy_new/venv/lib/python3.13/site-packages/mypy/build.py", line 3346, in process_graph
-   File "/tmp/mypy_primer/mypy_old/venv/lib/python3.13/site-packages/mypy/build.py", line 3475, in process_stale_scc
+   File "/tmp/mypy_primer/mypy_new/venv/lib/python3.13/site-packages/mypy/build.py", line 3475, in process_stale_scc
-   File "/tmp/mypy_primer/mypy_old/venv/lib/python3.13/site-packages/mypy/build.py", line 2493, in write_cache
+   File "/tmp/mypy_primer/mypy_new/venv/lib/python3.13/site-packages/mypy/build.py", line 2493, in write_cache
-   File "/tmp/mypy_primer/mypy_old/venv/lib/python3.13/site-packages/mypy/cache.py", line 28, in __init__
+   File "/tmp/mypy_primer/mypy_new/venv/lib/python3.13/site-packages/mypy/cache.py", line 28, in __init__