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This implements the stopgap approach described in https://github.com/astral-sh/ty/issues/336#issuecomment-2880532213 for handling literal types in generic class specializations. With this approach, we will promote any literal to its instance type, but _only_ when inferring a generic class specialization from a constructor call: ```py class C[T]: def __init__(self, x: T) -> None: ... reveal_type(C("string")) # revealed: C[str] ``` If you specialize the class explicitly, we still use whatever type you provide, even if it's a literal: ```py from typing import Literal reveal_type(C[Literal[5]](5)) # revealed: C[Literal[5]] ``` And this doesn't apply at all to generic functions: ```py def f[T](x: T) -> T: return x reveal_type(f(5)) # revealed: Literal[5] ``` --- As part of making this happen, we also generalize the `TypeMapping` machinery. This provides a way to apply a function to type, returning a new type. Complicating matters is that for function literals, we have to apply the mapping lazily, since the function's signature is not created until (and if) someone calls its `signature` method. That means we have to stash away the mappings that we want to apply to the signatures parameter/return annotations once we do create it. This requires some minor `Cow` shenanigans to continue working for partial specializations. |
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| .. | ||
| annotations | ||
| assignment | ||
| binary | ||
| boolean | ||
| boundness_declaredness | ||
| call | ||
| class | ||
| comparison | ||
| comprehensions | ||
| conditional | ||
| declaration | ||
| diagnostics | ||
| directives | ||
| doc | ||
| exception | ||
| expression | ||
| function | ||
| generics | ||
| import | ||
| literal | ||
| loops | ||
| narrow | ||
| regression | ||
| scopes | ||
| shadowing | ||
| snapshots | ||
| stubs | ||
| subscript | ||
| suppressions | ||
| type_of | ||
| type_properties | ||
| type_qualifiers | ||
| unary | ||
| with | ||
| .mdformat.toml | ||
| attributes.md | ||
| cycle.md | ||
| dataclass_transform.md | ||
| dataclasses.md | ||
| decorators.md | ||
| descriptor_protocol.md | ||
| final.md | ||
| intersection_types.md | ||
| invalid_syntax.md | ||
| known_constants.md | ||
| mdtest_config.md | ||
| mdtest_custom_typeshed.md | ||
| metaclass.md | ||
| mro.md | ||
| named_tuple.md | ||
| overloads.md | ||
| pep695_type_aliases.md | ||
| properties.md | ||
| protocols.md | ||
| slots.md | ||
| statically_known_branches.md | ||
| sys_platform.md | ||
| sys_version_info.md | ||
| terminal_statements.md | ||
| type_api.md | ||
| typed_dict.md | ||
| union_types.md | ||
| unpacking.md | ||
| unreachable.md | ||