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- """Utilities for type argument inference."""
- from __future__ import annotations
- from typing import NamedTuple, Sequence
- from mypy.constraints import (
- SUBTYPE_OF,
- SUPERTYPE_OF,
- infer_constraints,
- infer_constraints_for_callable,
- )
- from mypy.nodes import ArgKind
- from mypy.solve import solve_constraints
- from mypy.types import CallableType, Instance, Type, TypeVarId
- class ArgumentInferContext(NamedTuple):
- """Type argument inference context.
- We need this because we pass around ``Mapping`` and ``Iterable`` types.
- These types are only known by ``TypeChecker`` itself.
- It is required for ``*`` and ``**`` argument inference.
- https://github.com/python/mypy/issues/11144
- """
- mapping_type: Instance
- iterable_type: Instance
- def infer_function_type_arguments(
- callee_type: CallableType,
- arg_types: Sequence[Type | None],
- arg_kinds: list[ArgKind],
- formal_to_actual: list[list[int]],
- context: ArgumentInferContext,
- strict: bool = True,
- ) -> list[Type | None]:
- """Infer the type arguments of a generic function.
- Return an array of lower bound types for the type variables -1 (at
- index 0), -2 (at index 1), etc. A lower bound is None if a value
- could not be inferred.
- Arguments:
- callee_type: the target generic function
- arg_types: argument types at the call site (each optional; if None,
- we are not considering this argument in the current pass)
- arg_kinds: nodes.ARG_* values for arg_types
- formal_to_actual: mapping from formal to actual variable indices
- """
- # Infer constraints.
- constraints = infer_constraints_for_callable(
- callee_type, arg_types, arg_kinds, formal_to_actual, context
- )
- # Solve constraints.
- type_vars = callee_type.type_var_ids()
- return solve_constraints(type_vars, constraints, strict)
- def infer_type_arguments(
- type_var_ids: list[TypeVarId], template: Type, actual: Type, is_supertype: bool = False
- ) -> list[Type | None]:
- # Like infer_function_type_arguments, but only match a single type
- # against a generic type.
- constraints = infer_constraints(template, actual, SUPERTYPE_OF if is_supertype else SUBTYPE_OF)
- return solve_constraints(type_var_ids, constraints)
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