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