| """Utilities for type argument inference.""" |
| |
| from typing import List, Optional |
| |
| from mypy.constraints import infer_constraints, infer_constraints_for_callable |
| from mypy.types import Type, TypeVarId, CallableType |
| from mypy.solve import solve_constraints |
| from mypy.constraints import SUBTYPE_OF |
| |
| |
| def infer_function_type_arguments(callee_type: CallableType, |
| arg_types: List[Optional[Type]], |
| arg_kinds: List[int], |
| formal_to_actual: List[List[int]], |
| strict: bool = True) -> List[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) |
| |
| # 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) -> List[Type]: |
| # Like infer_function_type_arguments, but only match a single type |
| # against a generic type. |
| constraints = infer_constraints(template, actual, SUBTYPE_OF) |
| return solve_constraints(type_var_ids, constraints) |