Current File : //lib/python3/dist-packages/mypy/infer.py
"""Utilities for type argument inference."""
from typing import List, Optional, Sequence, NamedTuple
from mypy.constraints import (
infer_constraints, infer_constraints_for_callable, SUBTYPE_OF, SUPERTYPE_OF
)
from mypy.types import Type, TypeVarId, CallableType, Instance
from mypy.nodes import ArgKind
from mypy.solve import solve_constraints
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[Optional[Type]],
arg_kinds: List[ArgKind],
formal_to_actual: List[List[int]],
context: ArgumentInferContext,
strict: bool = True) -> List[Optional[Type]]:
"""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[Optional[Type]]:
# 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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