/usr/lib/python3/dist-packages/mypy/join.py is in python3-mypy 0.560-1.
This file is owned by root:root, with mode 0o644.
The actual contents of the file can be viewed below.
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 101 102 103 104 105 106 107 108 109 110 111 112 113 114 115 116 117 118 119 120 121 122 123 124 125 126 127 128 129 130 131 132 133 134 135 136 137 138 139 140 141 142 143 144 145 146 147 148 149 150 151 152 153 154 155 156 157 158 159 160 161 162 163 164 165 166 167 168 169 170 171 172 173 174 175 176 177 178 179 180 181 182 183 184 185 186 187 188 189 190 191 192 193 194 195 196 197 198 199 200 201 202 203 204 205 206 207 208 209 210 211 212 213 214 215 216 217 218 219 220 221 222 223 224 225 226 227 228 229 230 231 232 233 234 235 236 237 238 239 240 241 242 243 244 245 246 247 248 249 250 251 252 253 254 255 256 257 258 259 260 261 262 263 264 265 266 267 268 269 270 271 272 273 274 275 276 277 278 279 280 281 282 283 284 285 286 287 288 289 290 291 292 293 294 295 296 297 298 299 300 301 302 303 304 305 306 307 308 309 310 311 312 313 314 315 316 317 318 319 320 321 322 323 324 325 326 327 328 329 330 331 332 333 334 335 336 337 338 339 340 341 342 343 344 345 346 347 348 349 350 351 352 353 354 355 356 357 358 359 360 361 362 363 364 365 366 367 368 369 370 371 372 373 374 375 376 377 378 379 380 381 382 383 384 385 386 387 388 389 390 391 392 393 394 395 396 397 398 399 400 401 402 403 404 405 406 | """Calculation of the least upper bound types (joins)."""
from collections import OrderedDict
from typing import cast, List, Optional
from mypy.types import (
Type, AnyType, NoneTyp, TypeVisitor, Instance, UnboundType, TypeVarType, CallableType,
TupleType, TypedDictType, ErasedType, TypeList, UnionType, FunctionLike, Overloaded,
PartialType, DeletedType, UninhabitedType, TypeType, true_or_false, TypeOfAny
)
from mypy.maptype import map_instance_to_supertype
from mypy.subtypes import (
is_subtype, is_equivalent, is_subtype_ignoring_tvars, is_proper_subtype,
is_protocol_implementation
)
from mypy import experiments
def join_simple(declaration: Optional[Type], s: Type, t: Type) -> Type:
"""Return a simple least upper bound given the declared type."""
if (s.can_be_true, s.can_be_false) != (t.can_be_true, t.can_be_false):
# if types are restricted in different ways, use the more general versions
s = true_or_false(s)
t = true_or_false(t)
if isinstance(s, AnyType):
return s
if isinstance(s, ErasedType):
return t
if is_proper_subtype(s, t):
return t
if is_proper_subtype(t, s):
return s
if isinstance(declaration, UnionType):
return UnionType.make_simplified_union([s, t])
if isinstance(s, NoneTyp) and not isinstance(t, NoneTyp):
s, t = t, s
if isinstance(s, UninhabitedType) and not isinstance(t, UninhabitedType):
s, t = t, s
value = t.accept(TypeJoinVisitor(s))
if value is None:
# XXX this code path probably should be avoided.
# It seems to happen when a line (x = y) is a type error, and
# it's not clear that assuming that x is arbitrary afterward
# is a good idea.
return declaration
if declaration is None or is_subtype(value, declaration):
return value
return declaration
def join_types(s: Type, t: Type) -> Type:
"""Return the least upper bound of s and t.
For example, the join of 'int' and 'object' is 'object'.
"""
if (s.can_be_true, s.can_be_false) != (t.can_be_true, t.can_be_false):
# if types are restricted in different ways, use the more general versions
s = true_or_false(s)
t = true_or_false(t)
if isinstance(s, AnyType):
return s
if isinstance(s, ErasedType):
return t
if isinstance(s, UnionType) and not isinstance(t, UnionType):
s, t = t, s
if isinstance(s, NoneTyp) and not isinstance(t, NoneTyp):
s, t = t, s
if isinstance(s, UninhabitedType) and not isinstance(t, UninhabitedType):
s, t = t, s
# Use a visitor to handle non-trivial cases.
return t.accept(TypeJoinVisitor(s))
class TypeJoinVisitor(TypeVisitor[Type]):
"""Implementation of the least upper bound algorithm.
Attributes:
s: The other (left) type operand.
"""
def __init__(self, s: Type) -> None:
self.s = s
def visit_unbound_type(self, t: UnboundType) -> Type:
return AnyType(TypeOfAny.special_form)
def visit_union_type(self, t: UnionType) -> Type:
if is_subtype(self.s, t):
return t
else:
return UnionType.make_simplified_union([self.s, t])
def visit_any(self, t: AnyType) -> Type:
return t
def visit_none_type(self, t: NoneTyp) -> Type:
if experiments.STRICT_OPTIONAL:
if isinstance(self.s, (NoneTyp, UninhabitedType)):
return t
elif isinstance(self.s, UnboundType):
return AnyType(TypeOfAny.special_form)
else:
return UnionType.make_simplified_union([self.s, t])
else:
return self.s
def visit_uninhabited_type(self, t: UninhabitedType) -> Type:
return self.s
def visit_deleted_type(self, t: DeletedType) -> Type:
return self.s
def visit_erased_type(self, t: ErasedType) -> Type:
return self.s
def visit_type_var(self, t: TypeVarType) -> Type:
if isinstance(self.s, TypeVarType) and self.s.id == t.id:
return self.s
else:
return self.default(self.s)
def visit_instance(self, t: Instance) -> Type:
if isinstance(self.s, Instance):
nominal = join_instances(t, self.s)
structural = None # type: Optional[Instance]
if t.type.is_protocol and is_protocol_implementation(self.s, t):
structural = t
elif self.s.type.is_protocol and is_protocol_implementation(t, self.s):
structural = self.s
# Structural join is preferred in the case where we have found both
# structural and nominal and they have same MRO length (see two comments
# in join_instances_via_supertype). Otherwise, just return the nominal join.
if not structural or is_better(nominal, structural):
return nominal
return structural
elif isinstance(self.s, FunctionLike):
return join_types(t, self.s.fallback)
elif isinstance(self.s, TypeType):
return join_types(t, self.s)
elif isinstance(self.s, TypedDictType):
return join_types(t, self.s)
else:
return self.default(self.s)
def visit_callable_type(self, t: CallableType) -> Type:
if isinstance(self.s, CallableType) and is_similar_callables(t, self.s):
if is_equivalent(t, self.s):
return combine_similar_callables(t, self.s)
result = join_similar_callables(t, self.s)
if any(isinstance(tp, (NoneTyp, UninhabitedType)) for tp in result.arg_types):
# We don't want to return unusable Callable, attempt fallback instead.
return join_types(t.fallback, self.s)
return result
elif isinstance(self.s, Overloaded):
# Switch the order of arguments to that we'll get to visit_overloaded.
return join_types(t, self.s)
else:
return join_types(t.fallback, self.s)
def visit_overloaded(self, t: Overloaded) -> Type:
# This is more complex than most other cases. Here are some
# examples that illustrate how this works.
#
# First let's define a concise notation:
# - Cn are callable types (for n in 1, 2, ...)
# - Ov(C1, C2, ...) is an overloaded type with items C1, C2, ...
# - Callable[[T, ...], S] is written as [T, ...] -> S.
#
# We want some basic properties to hold (assume Cn are all
# unrelated via Any-similarity):
#
# join(Ov(C1, C2), C1) == C1
# join(Ov(C1, C2), Ov(C1, C2)) == Ov(C1, C2)
# join(Ov(C1, C2), Ov(C1, C3)) == C1
# join(Ov(C2, C2), C3) == join of fallback types
#
# The presence of Any types makes things more interesting. The join is the
# most general type we can get with respect to Any:
#
# join(Ov([int] -> int, [str] -> str), [Any] -> str) == Any -> str
#
# We could use a simplification step that removes redundancies, but that's not
# implemented right now. Consider this example, where we get a redundancy:
#
# join(Ov([int, Any] -> Any, [str, Any] -> Any), [Any, int] -> Any) ==
# Ov([Any, int] -> Any, [Any, int] -> Any)
#
# TODO: Consider more cases of callable subtyping.
result = [] # type: List[CallableType]
s = self.s
if isinstance(s, FunctionLike):
# The interesting case where both types are function types.
for t_item in t.items():
for s_item in s.items():
if is_similar_callables(t_item, s_item):
if is_equivalent(t_item, s_item):
result.append(combine_similar_callables(t_item, s_item))
elif is_subtype(t_item, s_item):
result.append(s_item)
if result:
# TODO: Simplify redundancies from the result.
if len(result) == 1:
return result[0]
else:
return Overloaded(result)
return join_types(t.fallback, s.fallback)
return join_types(t.fallback, s)
def visit_tuple_type(self, t: TupleType) -> Type:
if isinstance(self.s, TupleType) and self.s.length() == t.length():
items = [] # type: List[Type]
for i in range(t.length()):
items.append(self.join(t.items[i], self.s.items[i]))
fallback = join_instances(self.s.fallback, t.fallback)
assert isinstance(fallback, Instance)
return TupleType(items, fallback)
else:
return self.default(self.s)
def visit_typeddict_type(self, t: TypedDictType) -> Type:
if isinstance(self.s, TypedDictType):
items = OrderedDict([
(item_name, s_item_type)
for (item_name, s_item_type, t_item_type) in self.s.zip(t)
if (is_equivalent(s_item_type, t_item_type) and
(item_name in t.required_keys) == (item_name in self.s.required_keys))
])
mapping_value_type = join_type_list(list(items.values()))
fallback = self.s.create_anonymous_fallback(value_type=mapping_value_type)
# We need to filter by items.keys() since some required keys present in both t and
# self.s might be missing from the join if the types are incompatible.
required_keys = set(items.keys()) & t.required_keys & self.s.required_keys
return TypedDictType(items, required_keys, fallback)
elif isinstance(self.s, Instance):
return join_types(self.s, t.fallback)
else:
return self.default(self.s)
def visit_partial_type(self, t: PartialType) -> Type:
# We only have partial information so we can't decide the join result. We should
# never get here.
assert False, "Internal error"
def visit_type_type(self, t: TypeType) -> Type:
if isinstance(self.s, TypeType):
return TypeType.make_normalized(self.join(t.item, self.s.item), line=t.line)
elif isinstance(self.s, Instance) and self.s.type.fullname() == 'builtins.type':
return self.s
else:
return self.default(self.s)
def join(self, s: Type, t: Type) -> Type:
return join_types(s, t)
def default(self, typ: Type) -> Type:
if isinstance(typ, Instance):
return object_from_instance(typ)
elif isinstance(typ, UnboundType):
return AnyType(TypeOfAny.special_form)
elif isinstance(typ, TupleType):
return self.default(typ.fallback)
elif isinstance(typ, TypedDictType):
return self.default(typ.fallback)
elif isinstance(typ, FunctionLike):
return self.default(typ.fallback)
elif isinstance(typ, TypeVarType):
return self.default(typ.upper_bound)
else:
return AnyType(TypeOfAny.special_form)
def join_instances(t: Instance, s: Instance) -> Type:
"""Calculate the join of two instance types.
"""
if t.type == s.type:
# Simplest case: join two types with the same base type (but
# potentially different arguments).
if is_subtype(t, s) or is_subtype(s, t):
# Compatible; combine type arguments.
args = [] # type: List[Type]
for i in range(len(t.args)):
args.append(join_types(t.args[i], s.args[i]))
return Instance(t.type, args)
else:
# Incompatible; return trivial result object.
return object_from_instance(t)
elif t.type.bases and is_subtype_ignoring_tvars(t, s):
return join_instances_via_supertype(t, s)
else:
# Now t is not a subtype of s, and t != s. Now s could be a subtype
# of t; alternatively, we need to find a common supertype. This works
# in of the both cases.
return join_instances_via_supertype(s, t)
def join_instances_via_supertype(t: Instance, s: Instance) -> Type:
# Give preference to joins via duck typing relationship, so that
# join(int, float) == float, for example.
if t.type._promote and is_subtype(t.type._promote, s):
return join_types(t.type._promote, s)
elif s.type._promote and is_subtype(s.type._promote, t):
return join_types(t, s.type._promote)
# Compute the "best" supertype of t when joined with s.
# The definition of "best" may evolve; for now it is the one with
# the longest MRO. Ties are broken by using the earlier base.
best = None # type: Optional[Type]
for base in t.type.bases:
mapped = map_instance_to_supertype(t, base.type)
res = join_instances(mapped, s)
if best is None or is_better(res, best):
best = res
assert best is not None
return best
def is_better(t: Type, s: Type) -> bool:
# Given two possible results from join_instances_via_supertype(),
# indicate whether t is the better one.
if isinstance(t, Instance):
if not isinstance(s, Instance):
return True
# Use len(mro) as a proxy for the better choice.
if len(t.type.mro) > len(s.type.mro):
return True
return False
def is_similar_callables(t: CallableType, s: CallableType) -> bool:
"""Return True if t and s have identical numbers of
arguments, default arguments and varargs.
"""
return (len(t.arg_types) == len(s.arg_types) and t.min_args == s.min_args and
t.is_var_arg == s.is_var_arg)
def join_similar_callables(t: CallableType, s: CallableType) -> CallableType:
from mypy.meet import meet_types
arg_types = [] # type: List[Type]
for i in range(len(t.arg_types)):
arg_types.append(meet_types(t.arg_types[i], s.arg_types[i]))
# TODO in combine_similar_callables also applies here (names and kinds)
# The fallback type can be either 'function' or 'type'. The result should have 'type' as
# fallback only if both operands have it as 'type'.
if t.fallback.type.fullname() != 'builtins.type':
fallback = t.fallback
else:
fallback = s.fallback
return t.copy_modified(arg_types=arg_types,
ret_type=join_types(t.ret_type, s.ret_type),
fallback=fallback,
name=None)
def combine_similar_callables(t: CallableType, s: CallableType) -> CallableType:
arg_types = [] # type: List[Type]
for i in range(len(t.arg_types)):
arg_types.append(join_types(t.arg_types[i], s.arg_types[i]))
# TODO kinds and argument names
# The fallback type can be either 'function' or 'type'. The result should have 'type' as
# fallback only if both operands have it as 'type'.
if t.fallback.type.fullname() != 'builtins.type':
fallback = t.fallback
else:
fallback = s.fallback
return t.copy_modified(arg_types=arg_types,
ret_type=join_types(t.ret_type, s.ret_type),
fallback=fallback,
name=None)
def object_from_instance(instance: Instance) -> Instance:
"""Construct the type 'builtins.object' from an instance type."""
# Use the fact that 'object' is always the last class in the mro.
res = Instance(instance.type.mro[-1], [])
return res
def join_type_list(types: List[Type]) -> Type:
if not types:
# This is a little arbitrary but reasonable. Any empty tuple should be compatible
# with all variable length tuples, and this makes it possible.
return UninhabitedType()
joined = types[0]
for t in types[1:]:
joined = join_types(joined, t)
return joined
|