"""Type inference constraints.""" from typing import TYPE_CHECKING, Iterable, List, Optional, Sequence from typing_extensions import Final from mypy.types import ( CallableType, Type, TypeVisitor, UnboundType, AnyType, NoneType, TypeVarType, Instance, TupleType, TypedDictType, UnionType, Overloaded, ErasedType, PartialType, DeletedType, UninhabitedType, TypeType, TypeVarId, TypeQuery, is_named_instance, TypeOfAny, LiteralType, ProperType, ParamSpecType, get_proper_type, TypeAliasType, is_union_with_any, UnpackType, callable_with_ellipsis, Parameters, TUPLE_LIKE_INSTANCE_NAMES, TypeVarTupleType, ) from mypy.maptype import map_instance_to_supertype import mypy.subtypes import mypy.sametypes import mypy.typeops from mypy.erasetype import erase_typevars from mypy.nodes import COVARIANT, CONTRAVARIANT, ArgKind from mypy.argmap import ArgTypeExpander from mypy.typestate import TypeState if TYPE_CHECKING: from mypy.infer import ArgumentInferContext SUBTYPE_OF: Final = 0 SUPERTYPE_OF: Final = 1 class Constraint: """A representation of a type constraint. It can be either T <: type or T :> type (T is a type variable). """ type_var: TypeVarId op = 0 # SUBTYPE_OF or SUPERTYPE_OF target: Type def __init__(self, type_var: TypeVarId, op: int, target: Type) -> None: self.type_var = type_var self.op = op self.target = target def __repr__(self) -> str: op_str = '<:' if self.op == SUPERTYPE_OF: op_str = ':>' return f'{self.type_var} {op_str} {self.target}' def infer_constraints_for_callable( callee: CallableType, arg_types: Sequence[Optional[Type]], arg_kinds: List[ArgKind], formal_to_actual: List[List[int]], context: 'ArgumentInferContext') -> List[Constraint]: """Infer type variable constraints for a callable and actual arguments. Return a list of constraints. """ constraints: List[Constraint] = [] mapper = ArgTypeExpander(context) for i, actuals in enumerate(formal_to_actual): for actual in actuals: actual_arg_type = arg_types[actual] if actual_arg_type is None: continue actual_type = mapper.expand_actual_type(actual_arg_type, arg_kinds[actual], callee.arg_names[i], callee.arg_kinds[i]) c = infer_constraints(callee.arg_types[i], actual_type, SUPERTYPE_OF) constraints.extend(c) return constraints def infer_constraints(template: Type, actual: Type, direction: int) -> List[Constraint]: """Infer type constraints. Match a template type, which may contain type variable references, recursively against a type which does not contain (the same) type variable references. The result is a list of type constrains of form 'T is a supertype/subtype of x', where T is a type variable present in the template and x is a type without reference to type variables present in the template. Assume T and S are type variables. Now the following results can be calculated (read as '(template, actual) --> result'): (T, X) --> T :> X (X[T], X[Y]) --> T <: Y and T :> Y ((T, T), (X, Y)) --> T :> X and T :> Y ((T, S), (X, Y)) --> T :> X and S :> Y (X[T], Any) --> T <: Any and T :> Any The constraints are represented as Constraint objects. """ if any(get_proper_type(template) == get_proper_type(t) for t in TypeState._inferring): return [] if isinstance(template, TypeAliasType) and template.is_recursive: # This case requires special care because it may cause infinite recursion. TypeState._inferring.append(template) res = _infer_constraints(template, actual, direction) TypeState._inferring.pop() return res return _infer_constraints(template, actual, direction) def _infer_constraints(template: Type, actual: Type, direction: int) -> List[Constraint]: orig_template = template template = get_proper_type(template) actual = get_proper_type(actual) # Type inference shouldn't be affected by whether union types have been simplified. # We however keep any ErasedType items, so that the caller will see it when using # checkexpr.has_erased_component(). if isinstance(template, UnionType): template = mypy.typeops.make_simplified_union(template.items, keep_erased=True) if isinstance(actual, UnionType): actual = mypy.typeops.make_simplified_union(actual.items, keep_erased=True) # Ignore Any types from the type suggestion engine to avoid them # causing us to infer Any in situations where a better job could # be done otherwise. (This can produce false positives but that # doesn't really matter because it is all heuristic anyway.) if isinstance(actual, AnyType) and actual.type_of_any == TypeOfAny.suggestion_engine: return [] # If the template is simply a type variable, emit a Constraint directly. # We need to handle this case before handling Unions for two reasons: # 1. "T <: Union[U1, U2]" is not equivalent to "T <: U1 or T <: U2", # because T can itself be a union (notably, Union[U1, U2] itself). # 2. "T :> Union[U1, U2]" is logically equivalent to "T :> U1 and # T :> U2", but they are not equivalent to the constraint solver, # which never introduces new Union types (it uses join() instead). if isinstance(template, TypeVarType): return [Constraint(template.id, direction, actual)] # Now handle the case of either template or actual being a Union. # For a Union to be a subtype of another type, every item of the Union # must be a subtype of that type, so concatenate the constraints. if direction == SUBTYPE_OF and isinstance(template, UnionType): res = [] for t_item in template.items: res.extend(infer_constraints(t_item, actual, direction)) return res if direction == SUPERTYPE_OF and isinstance(actual, UnionType): res = [] for a_item in actual.items: res.extend(infer_constraints(orig_template, a_item, direction)) return res # Now the potential subtype is known not to be a Union or a type # variable that we are solving for. In that case, for a Union to # be a supertype of the potential subtype, some item of the Union # must be a supertype of it. if direction == SUBTYPE_OF and isinstance(actual, UnionType): # If some of items is not a complete type, disregard that. items = simplify_away_incomplete_types(actual.items) # We infer constraints eagerly -- try to find constraints for a type # variable if possible. This seems to help with some real-world # use cases. return any_constraints( [infer_constraints_if_possible(template, a_item, direction) for a_item in items], eager=True) if direction == SUPERTYPE_OF and isinstance(template, UnionType): # When the template is a union, we are okay with leaving some # type variables indeterminate. This helps with some special # cases, though this isn't very principled. return any_constraints( [infer_constraints_if_possible(t_item, actual, direction) for t_item in template.items], eager=False) # Remaining cases are handled by ConstraintBuilderVisitor. return template.accept(ConstraintBuilderVisitor(actual, direction)) def infer_constraints_if_possible(template: Type, actual: Type, direction: int) -> Optional[List[Constraint]]: """Like infer_constraints, but return None if the input relation is known to be unsatisfiable, for example if template=List[T] and actual=int. (In this case infer_constraints would return [], just like it would for an automatically satisfied relation like template=List[T] and actual=object.) """ if (direction == SUBTYPE_OF and not mypy.subtypes.is_subtype(erase_typevars(template), actual)): return None if (direction == SUPERTYPE_OF and not mypy.subtypes.is_subtype(actual, erase_typevars(template))): return None if (direction == SUPERTYPE_OF and isinstance(template, TypeVarType) and not mypy.subtypes.is_subtype(actual, erase_typevars(template.upper_bound))): # This is not caught by the above branch because of the erase_typevars() call, # that would return 'Any' for a type variable. return None return infer_constraints(template, actual, direction) def select_trivial(options: Sequence[Optional[List[Constraint]]]) -> List[List[Constraint]]: """Select only those lists where each item is a constraint against Any.""" res = [] for option in options: if option is None: continue if all(isinstance(get_proper_type(c.target), AnyType) for c in option): res.append(option) return res def merge_with_any(constraint: Constraint) -> Constraint: """Transform a constraint target into a union with given Any type.""" target = constraint.target if is_union_with_any(target): # Do not produce redundant unions. return constraint # TODO: if we will support multiple sources Any, use this here instead. any_type = AnyType(TypeOfAny.implementation_artifact) return Constraint( constraint.type_var, constraint.op, UnionType.make_union([target, any_type], target.line, target.column), ) def any_constraints(options: List[Optional[List[Constraint]]], eager: bool) -> List[Constraint]: """Deduce what we can from a collection of constraint lists. It's a given that at least one of the lists must be satisfied. A None element in the list of options represents an unsatisfiable constraint and is ignored. Ignore empty constraint lists if eager is true -- they are always trivially satisfiable. """ if eager: valid_options = [option for option in options if option] else: valid_options = [option for option in options if option is not None] if not valid_options: return [] if len(valid_options) == 1: return valid_options[0] if all(is_same_constraints(valid_options[0], c) for c in valid_options[1:]): # Multiple sets of constraints that are all the same. Just pick any one of them. return valid_options[0] if all(is_similar_constraints(valid_options[0], c) for c in valid_options[1:]): # All options have same structure. In this case we can merge-in trivial # options (i.e. those that only have Any) and try again. # TODO: More generally, if a given (variable, direction) pair appears in # every option, combine the bounds with meet/join always, not just for Any. trivial_options = select_trivial(valid_options) if trivial_options and len(trivial_options) < len(valid_options): merged_options = [] for option in valid_options: if option in trivial_options: continue if option is not None: merged_option: Optional[List[Constraint]] = [ merge_with_any(c) for c in option ] else: merged_option = None merged_options.append(merged_option) return any_constraints([option for option in merged_options], eager) # Otherwise, there are either no valid options or multiple, inconsistent valid # options. Give up and deduce nothing. return [] def is_same_constraints(x: List[Constraint], y: List[Constraint]) -> bool: for c1 in x: if not any(is_same_constraint(c1, c2) for c2 in y): return False for c1 in y: if not any(is_same_constraint(c1, c2) for c2 in x): return False return True def is_same_constraint(c1: Constraint, c2: Constraint) -> bool: # Ignore direction when comparing constraints against Any. skip_op_check = ( isinstance(get_proper_type(c1.target), AnyType) and isinstance(get_proper_type(c2.target), AnyType) ) return (c1.type_var == c2.type_var and (c1.op == c2.op or skip_op_check) and mypy.sametypes.is_same_type(c1.target, c2.target)) def is_similar_constraints(x: List[Constraint], y: List[Constraint]) -> bool: """Check that two lists of constraints have similar structure. This means that each list has same type variable plus direction pairs (i.e we ignore the target). Except for constraints where target is Any type, there we ignore direction as well. """ return _is_similar_constraints(x, y) and _is_similar_constraints(y, x) def _is_similar_constraints(x: List[Constraint], y: List[Constraint]) -> bool: """Check that every constraint in the first list has a similar one in the second. See docstring above for definition of similarity. """ for c1 in x: has_similar = False for c2 in y: # Ignore direction when either constraint is against Any. skip_op_check = ( isinstance(get_proper_type(c1.target), AnyType) or isinstance(get_proper_type(c2.target), AnyType) ) if c1.type_var == c2.type_var and (c1.op == c2.op or skip_op_check): has_similar = True break if not has_similar: return False return True def simplify_away_incomplete_types(types: Iterable[Type]) -> List[Type]: complete = [typ for typ in types if is_complete_type(typ)] if complete: return complete else: return list(types) def is_complete_type(typ: Type) -> bool: """Is a type complete? A complete doesn't have uninhabited type components or (when not in strict optional mode) None components. """ return typ.accept(CompleteTypeVisitor()) class CompleteTypeVisitor(TypeQuery[bool]): def __init__(self) -> None: super().__init__(all) def visit_uninhabited_type(self, t: UninhabitedType) -> bool: return False class ConstraintBuilderVisitor(TypeVisitor[List[Constraint]]): """Visitor class for inferring type constraints.""" # The type that is compared against a template # TODO: The value may be None. Is that actually correct? actual: ProperType def __init__(self, actual: ProperType, direction: int) -> None: # Direction must be SUBTYPE_OF or SUPERTYPE_OF. self.actual = actual self.direction = direction # Trivial leaf types def visit_unbound_type(self, template: UnboundType) -> List[Constraint]: return [] def visit_any(self, template: AnyType) -> List[Constraint]: return [] def visit_none_type(self, template: NoneType) -> List[Constraint]: return [] def visit_uninhabited_type(self, template: UninhabitedType) -> List[Constraint]: return [] def visit_erased_type(self, template: ErasedType) -> List[Constraint]: return [] def visit_deleted_type(self, template: DeletedType) -> List[Constraint]: return [] def visit_literal_type(self, template: LiteralType) -> List[Constraint]: return [] # Errors def visit_partial_type(self, template: PartialType) -> List[Constraint]: # We can't do anything useful with a partial type here. assert False, "Internal error" # Non-trivial leaf type def visit_type_var(self, template: TypeVarType) -> List[Constraint]: assert False, ("Unexpected TypeVarType in ConstraintBuilderVisitor" " (should have been handled in infer_constraints)") def visit_param_spec(self, template: ParamSpecType) -> List[Constraint]: # Can't infer ParamSpecs from component values (only via Callable[P, T]). return [] def visit_type_var_tuple(self, template: TypeVarTupleType) -> List[Constraint]: raise NotImplementedError def visit_unpack_type(self, template: UnpackType) -> List[Constraint]: raise NotImplementedError def visit_parameters(self, template: Parameters) -> List[Constraint]: # constraining Any against C[P] turns into infer_against_any([P], Any) # ... which seems like the only case this can happen. Better to fail loudly. if isinstance(self.actual, AnyType): return self.infer_against_any(template.arg_types, self.actual) raise RuntimeError("Parameters cannot be constrained to") # Non-leaf types def visit_instance(self, template: Instance) -> List[Constraint]: original_actual = actual = self.actual res: List[Constraint] = [] if isinstance(actual, (CallableType, Overloaded)) and template.type.is_protocol: if template.type.protocol_members == ['__call__']: # Special case: a generic callback protocol if not any(mypy.sametypes.is_same_type(template, t) for t in template.type.inferring): template.type.inferring.append(template) call = mypy.subtypes.find_member('__call__', template, actual, is_operator=True) assert call is not None if mypy.subtypes.is_subtype(actual, erase_typevars(call)): subres = infer_constraints(call, actual, self.direction) res.extend(subres) template.type.inferring.pop() return res if isinstance(actual, CallableType) and actual.fallback is not None: actual = actual.fallback if isinstance(actual, Overloaded) and actual.fallback is not None: actual = actual.fallback if isinstance(actual, TypedDictType): actual = actual.as_anonymous().fallback if isinstance(actual, LiteralType): actual = actual.fallback if isinstance(actual, Instance): instance = actual erased = erase_typevars(template) assert isinstance(erased, Instance) # type: ignore # We always try nominal inference if possible, # it is much faster than the structural one. if (self.direction == SUBTYPE_OF and template.type.has_base(instance.type.fullname)): mapped = map_instance_to_supertype(template, instance.type) tvars = mapped.type.defn.type_vars # N.B: We use zip instead of indexing because the lengths might have # mismatches during daemon reprocessing. for tvar, mapped_arg, instance_arg in zip(tvars, mapped.args, instance.args): # TODO(PEP612): More ParamSpec work (or is Parameters the only thing accepted) if isinstance(tvar, TypeVarType): # The constraints for generic type parameters depend on variance. # Include constraints from both directions if invariant. if tvar.variance != CONTRAVARIANT: res.extend(infer_constraints( mapped_arg, instance_arg, self.direction)) if tvar.variance != COVARIANT: res.extend(infer_constraints( mapped_arg, instance_arg, neg_op(self.direction))) elif isinstance(tvar, ParamSpecType) and isinstance(mapped_arg, ParamSpecType): suffix = get_proper_type(instance_arg) if isinstance(suffix, CallableType): prefix = mapped_arg.prefix from_concat = bool(prefix.arg_types) or suffix.from_concatenate suffix = suffix.copy_modified(from_concatenate=from_concat) if isinstance(suffix, Parameters) or isinstance(suffix, CallableType): # no such thing as variance for ParamSpecs # TODO: is there a case I am missing? # TODO: constraints between prefixes prefix = mapped_arg.prefix suffix = suffix.copy_modified( suffix.arg_types[len(prefix.arg_types):], suffix.arg_kinds[len(prefix.arg_kinds):], suffix.arg_names[len(prefix.arg_names):]) res.append(Constraint(mapped_arg.id, SUPERTYPE_OF, suffix)) elif isinstance(suffix, ParamSpecType): res.append(Constraint(mapped_arg.id, SUPERTYPE_OF, suffix)) return res elif (self.direction == SUPERTYPE_OF and instance.type.has_base(template.type.fullname)): mapped = map_instance_to_supertype(instance, template.type) tvars = template.type.defn.type_vars # N.B: We use zip instead of indexing because the lengths might have # mismatches during daemon reprocessing. for tvar, mapped_arg, template_arg in zip(tvars, mapped.args, template.args): if isinstance(tvar, TypeVarType): # The constraints for generic type parameters depend on variance. # Include constraints from both directions if invariant. if tvar.variance != CONTRAVARIANT: res.extend(infer_constraints( template_arg, mapped_arg, self.direction)) if tvar.variance != COVARIANT: res.extend(infer_constraints( template_arg, mapped_arg, neg_op(self.direction))) elif (isinstance(tvar, ParamSpecType) and isinstance(template_arg, ParamSpecType)): suffix = get_proper_type(mapped_arg) if isinstance(suffix, CallableType): prefix = template_arg.prefix from_concat = bool(prefix.arg_types) or suffix.from_concatenate suffix = suffix.copy_modified(from_concatenate=from_concat) if isinstance(suffix, Parameters) or isinstance(suffix, CallableType): # no such thing as variance for ParamSpecs # TODO: is there a case I am missing? # TODO: constraints between prefixes prefix = template_arg.prefix suffix = suffix.copy_modified( suffix.arg_types[len(prefix.arg_types):], suffix.arg_kinds[len(prefix.arg_kinds):], suffix.arg_names[len(prefix.arg_names):]) res.append(Constraint(template_arg.id, SUPERTYPE_OF, suffix)) elif isinstance(suffix, ParamSpecType): res.append(Constraint(template_arg.id, SUPERTYPE_OF, suffix)) return res if (template.type.is_protocol and self.direction == SUPERTYPE_OF and # We avoid infinite recursion for structural subtypes by checking # whether this type already appeared in the inference chain. # This is a conservative way to break the inference cycles. # It never produces any "false" constraints but gives up soon # on purely structural inference cycles, see #3829. # Note that we use is_protocol_implementation instead of is_subtype # because some type may be considered a subtype of a protocol # due to _promote, but still not implement the protocol. not any(mypy.sametypes.is_same_type(template, t) for t in template.type.inferring) and mypy.subtypes.is_protocol_implementation(instance, erased)): template.type.inferring.append(template) res.extend(self.infer_constraints_from_protocol_members( instance, template, original_actual, template)) template.type.inferring.pop() return res elif (instance.type.is_protocol and self.direction == SUBTYPE_OF and # We avoid infinite recursion for structural subtypes also here. not any(mypy.sametypes.is_same_type(instance, i) for i in instance.type.inferring) and mypy.subtypes.is_protocol_implementation(erased, instance)): instance.type.inferring.append(instance) res.extend(self.infer_constraints_from_protocol_members( instance, template, template, instance)) instance.type.inferring.pop() return res if isinstance(actual, AnyType): return self.infer_against_any(template.args, actual) if (isinstance(actual, TupleType) and is_named_instance(template, TUPLE_LIKE_INSTANCE_NAMES) and self.direction == SUPERTYPE_OF): for item in actual.items: cb = infer_constraints(template.args[0], item, SUPERTYPE_OF) res.extend(cb) return res elif isinstance(actual, TupleType) and self.direction == SUPERTYPE_OF: return infer_constraints(template, mypy.typeops.tuple_fallback(actual), self.direction) elif isinstance(actual, TypeVarType): if not actual.values: return infer_constraints(template, actual.upper_bound, self.direction) return [] elif isinstance(actual, ParamSpecType): return infer_constraints(template, actual.upper_bound, self.direction) else: return [] def infer_constraints_from_protocol_members(self, instance: Instance, template: Instance, subtype: Type, protocol: Instance, ) -> List[Constraint]: """Infer constraints for situations where either 'template' or 'instance' is a protocol. The 'protocol' is the one of two that is an instance of protocol type, 'subtype' is the type used to bind self during inference. Currently, we just infer constrains for every protocol member type (both ways for settable members). """ res = [] for member in protocol.type.protocol_members: inst = mypy.subtypes.find_member(member, instance, subtype) temp = mypy.subtypes.find_member(member, template, subtype) if inst is None or temp is None: return [] # See #11020 # The above is safe since at this point we know that 'instance' is a subtype # of (erased) 'template', therefore it defines all protocol members res.extend(infer_constraints(temp, inst, self.direction)) if (mypy.subtypes.IS_SETTABLE in mypy.subtypes.get_member_flags(member, protocol.type)): # Settable members are invariant, add opposite constraints res.extend(infer_constraints(temp, inst, neg_op(self.direction))) return res def visit_callable_type(self, template: CallableType) -> List[Constraint]: if isinstance(self.actual, CallableType): res: List[Constraint] = [] cactual = self.actual param_spec = template.param_spec() if param_spec is None: # FIX verify argument counts # FIX what if one of the functions is generic # We can't infer constraints from arguments if the template is Callable[..., T] # (with literal '...'). if not template.is_ellipsis_args: # The lengths should match, but don't crash (it will error elsewhere). for t, a in zip(template.arg_types, cactual.arg_types): # Negate direction due to function argument type contravariance. res.extend(infer_constraints(t, a, neg_op(self.direction))) else: # sometimes, it appears we try to get constraints between two paramspec callables? # TODO: Direction # TODO: check the prefixes match prefix = param_spec.prefix prefix_len = len(prefix.arg_types) cactual_ps = cactual.param_spec() if not cactual_ps: res.append(Constraint(param_spec.id, SUBTYPE_OF, cactual.copy_modified( arg_types=cactual.arg_types[prefix_len:], arg_kinds=cactual.arg_kinds[prefix_len:], arg_names=cactual.arg_names[prefix_len:], ret_type=NoneType()))) else: res.append(Constraint(param_spec.id, SUBTYPE_OF, cactual_ps)) # compare prefixes cactual_prefix = cactual.copy_modified( arg_types=cactual.arg_types[:prefix_len], arg_kinds=cactual.arg_kinds[:prefix_len], arg_names=cactual.arg_names[:prefix_len]) # TODO: see above "FIX" comments for param_spec is None case # TODO: this assume positional arguments for t, a in zip(prefix.arg_types, cactual_prefix.arg_types): res.extend(infer_constraints(t, a, neg_op(self.direction))) template_ret_type, cactual_ret_type = template.ret_type, cactual.ret_type if template.type_guard is not None: template_ret_type = template.type_guard if cactual.type_guard is not None: cactual_ret_type = cactual.type_guard res.extend(infer_constraints(template_ret_type, cactual_ret_type, self.direction)) return res elif isinstance(self.actual, AnyType): param_spec = template.param_spec() any_type = AnyType(TypeOfAny.from_another_any, source_any=self.actual) if param_spec is None: # FIX what if generic res = self.infer_against_any(template.arg_types, self.actual) else: res = [Constraint(param_spec.id, SUBTYPE_OF, callable_with_ellipsis(any_type, any_type, template.fallback))] res.extend(infer_constraints(template.ret_type, any_type, self.direction)) return res elif isinstance(self.actual, Overloaded): return self.infer_against_overloaded(self.actual, template) elif isinstance(self.actual, TypeType): return infer_constraints(template.ret_type, self.actual.item, self.direction) elif isinstance(self.actual, Instance): # Instances with __call__ method defined are considered structural # subtypes of Callable with a compatible signature. call = mypy.subtypes.find_member('__call__', self.actual, self.actual, is_operator=True) if call: return infer_constraints(template, call, self.direction) else: return [] else: return [] def infer_against_overloaded(self, overloaded: Overloaded, template: CallableType) -> List[Constraint]: # Create constraints by matching an overloaded type against a template. # This is tricky to do in general. We cheat by only matching against # the first overload item that is callable compatible. This # seems to work somewhat well, but we should really use a more # reliable technique. item = find_matching_overload_item(overloaded, template) return infer_constraints(template, item, self.direction) def visit_tuple_type(self, template: TupleType) -> List[Constraint]: actual = self.actual # TODO: Support other items in the tuple besides Unpack # TODO: Support subclasses of Tuple is_varlength_tuple = ( isinstance(actual, Instance) and actual.type.fullname == "builtins.tuple" ) unpack_index = find_unpack_in_tuple(template) if unpack_index is not None: unpack_item = get_proper_type(template.items[unpack_index]) assert isinstance(unpack_item, UnpackType) unpacked_type = get_proper_type(unpack_item.type) if isinstance(unpacked_type, TypeVarTupleType): if is_varlength_tuple: # This case is only valid when the unpack is the only # item in the tuple. # # TODO: We should support this in the case that all the items # in the tuple besides the unpack have the same type as the # varlength tuple's type. E.g. Tuple[int, ...] should be valid # where we expect Tuple[int, Unpack[Ts]], but not for Tuple[str, Unpack[Ts]]. assert len(template.items) == 1 if ( isinstance(actual, (TupleType, AnyType)) or is_varlength_tuple ): modified_actual = actual if isinstance(actual, TupleType): # Exclude the items from before and after the unpack index. head = unpack_index tail = len(template.items) - unpack_index - 1 if tail: modified_actual = actual.copy_modified( items=actual.items[head:-tail], ) else: modified_actual = actual.copy_modified( items=actual.items[head:], ) return [Constraint( type_var=unpacked_type.id, op=self.direction, target=modified_actual, )] if isinstance(actual, TupleType) and len(actual.items) == len(template.items): res: List[Constraint] = [] for i in range(len(template.items)): res.extend(infer_constraints(template.items[i], actual.items[i], self.direction)) return res elif isinstance(actual, AnyType): return self.infer_against_any(template.items, actual) else: return [] def visit_typeddict_type(self, template: TypedDictType) -> List[Constraint]: actual = self.actual if isinstance(actual, TypedDictType): res: List[Constraint] = [] # NOTE: Non-matching keys are ignored. Compatibility is checked # elsewhere so this shouldn't be unsafe. for (item_name, template_item_type, actual_item_type) in template.zip(actual): res.extend(infer_constraints(template_item_type, actual_item_type, self.direction)) return res elif isinstance(actual, AnyType): return self.infer_against_any(template.items.values(), actual) else: return [] def visit_union_type(self, template: UnionType) -> List[Constraint]: assert False, ("Unexpected UnionType in ConstraintBuilderVisitor" " (should have been handled in infer_constraints)") def visit_type_alias_type(self, template: TypeAliasType) -> List[Constraint]: assert False, f"This should be never called, got {template}" def infer_against_any(self, types: Iterable[Type], any_type: AnyType) -> List[Constraint]: res: List[Constraint] = [] for t in types: # Note that we ignore variance and simply always use the # original direction. This is because for Any targets direction is # irrelevant in most cases, see e.g. is_same_constraint(). res.extend(infer_constraints(t, any_type, self.direction)) return res def visit_overloaded(self, template: Overloaded) -> List[Constraint]: if isinstance(self.actual, CallableType): items = find_matching_overload_items(template, self.actual) else: items = template.items res: List[Constraint] = [] for t in items: res.extend(infer_constraints(t, self.actual, self.direction)) return res def visit_type_type(self, template: TypeType) -> List[Constraint]: if isinstance(self.actual, CallableType): return infer_constraints(template.item, self.actual.ret_type, self.direction) elif isinstance(self.actual, Overloaded): return infer_constraints(template.item, self.actual.items[0].ret_type, self.direction) elif isinstance(self.actual, TypeType): return infer_constraints(template.item, self.actual.item, self.direction) elif isinstance(self.actual, AnyType): return infer_constraints(template.item, self.actual, self.direction) else: return [] def neg_op(op: int) -> int: """Map SubtypeOf to SupertypeOf and vice versa.""" if op == SUBTYPE_OF: return SUPERTYPE_OF elif op == SUPERTYPE_OF: return SUBTYPE_OF else: raise ValueError(f'Invalid operator {op}') def find_matching_overload_item(overloaded: Overloaded, template: CallableType) -> CallableType: """Disambiguate overload item against a template.""" items = overloaded.items for item in items: # Return type may be indeterminate in the template, so ignore it when performing a # subtype check. if mypy.subtypes.is_callable_compatible(item, template, is_compat=mypy.subtypes.is_subtype, ignore_return=True): return item # Fall back to the first item if we can't find a match. This is totally arbitrary -- # maybe we should just bail out at this point. return items[0] def find_matching_overload_items(overloaded: Overloaded, template: CallableType) -> List[CallableType]: """Like find_matching_overload_item, but return all matches, not just the first.""" items = overloaded.items res = [] for item in items: # Return type may be indeterminate in the template, so ignore it when performing a # subtype check. if mypy.subtypes.is_callable_compatible(item, template, is_compat=mypy.subtypes.is_subtype, ignore_return=True): res.append(item) if not res: # Falling back to all items if we can't find a match is pretty arbitrary, but # it maintains backward compatibility. res = items[:] return res def find_unpack_in_tuple(t: TupleType) -> Optional[int]: unpack_index: Optional[int] = None for i, item in enumerate(t.items): proper_item = get_proper_type(item) if isinstance(proper_item, UnpackType): # We cannot fail here, so we must check this in an earlier # semanal phase. # Funky code here avoids mypyc narrowing the type of unpack_index. old_index = unpack_index assert old_index is None # Don't return so that we can also sanity check there is only one. unpack_index = i return unpack_index