from __future__ import annotations

from collections import defaultdict

from collections.abc import Iterator

from contextlib import contextmanager

from typing import Literal, NamedTuple, TypeAlias as _TypeAlias

from mypy.erasetype import remove_instance_last_known_values

from mypy.literals import Key, extract_var_from_literal_hash, literal, literal_hash, subkeys

from mypy.nodes import (

LITERAL_NO,

Expression,

IndexExpr,

MemberExpr,

NameExpr,

RefExpr,

TypeInfo,

Var,

)

from mypy.options import Options

from mypy.subtypes import is_same_type, is_subtype

from mypy.typeops import make_simplified_union

from mypy.types import (

AnyType,

Instance,

NoneType,

PartialType,

ProperType,

TupleType,

Type,

TypeOfAny,

TypeType,

TypeVarType,

UnionType,

UnpackType,

find_unpack_in_list,

flatten_nested_unions,

get_proper_type,

)

from mypy.typevars import fill_typevars_with_any

BindableExpression: _TypeAlias = IndexExpr | MemberExpr | NameExpr

class CurrentType(NamedTuple):

type: Type

from_assignment: bool

class Frame:

"""A Frame represents a specific point in the execution of a program.

It carries information about the current types of expressions at

that point, arising either from assignments to those expressions

or the result of isinstance checks and other type narrowing

operations. It also records whether it is possible to reach that

point at all.

We add a new frame wherenever there is a new scope or control flow

branching.

This information is not copied into a new Frame when it is pushed

onto the stack, so a given Frame only has information about types

that were assigned in that frame.

Expressions are stored in dicts using 'literal hashes' as keys (type

"Key"). These are hashable values derived from expression AST nodes

(only those that can be narrowed). literal_hash(expr) is used to

calculate the hashes. Note that this isn't directly related to literal

types -- the concept predates literal types.

"""

def __init__(self, id: int, conditional_frame: bool = False) -> None:

self.id = id

self.types: dict[Key, CurrentType] = {}

self.unreachable = False

self.conditional_frame = conditional_frame

self.suppress_unreachable_warnings = False

def __repr__(self) -> str:

return f"Frame({self.id}, {self.types}, {self.unreachable}, {self.conditional_frame})"

Assigns = defaultdict[Expression, list[tuple[Type, Type | None]]]

class FrameContext:

"""Context manager pushing a Frame to ConditionalTypeBinder.

See frame_context() below for documentation on parameters. We use this class

instead of @contextmanager as a mypyc-specific performance optimization.

"""

def __init__(

self,

binder: ConditionalTypeBinder,

can_skip: bool,

fall_through: int,

break_frame: int,

continue_frame: int,

conditional_frame: bool,

try_frame: bool,

discard: bool,

) -> None:

self.binder = binder

self.can_skip = can_skip

self.fall_through = fall_through

self.break_frame = break_frame

self.continue_frame = continue_frame

self.conditional_frame = conditional_frame

self.try_frame = try_frame

self.discard = discard

def __enter__(self) -> Frame:

assert len(self.binder.frames) > 1

if self.break_frame:

self.binder.break_frames.append(len(self.binder.frames) - self.break_frame)

if self.continue_frame:

self.binder.continue_frames.append(len(self.binder.frames) - self.continue_frame)

if self.try_frame:

self.binder.try_frames.add(len(self.binder.frames) - 1)

new_frame = self.binder.push_frame(self.conditional_frame)

if self.try_frame:

# An exception may occur immediately

self.binder.allow_jump(-1)

return new_frame

def __exit__(self, exc_type: object, exc_val: object, exc_tb: object) -> Literal[False]:

self.binder.pop_frame(self.can_skip, self.fall_through, discard=self.discard)

if self.break_frame:

self.binder.break_frames.pop()

if self.continue_frame:

self.binder.continue_frames.pop()

if self.try_frame:

self.binder.try_frames.remove(len(self.binder.frames) - 1)

return False

class ConditionalTypeBinder:

"""Keep track of conditional types of variables.

NB: Variables are tracked by literal hashes of expressions, so it is

possible to confuse the binder when there is aliasing. Example:

class A:

a: int | str

x = A()

lst = [x]

reveal_type(x.a) # int | str

x.a = 1

reveal_type(x.a) # int

reveal_type(lst[0].a) # int | str

lst[0].a = 'a'

reveal_type(x.a) # int

reveal_type(lst[0].a) # str

"""

# Stored assignments for situations with tuple/list lvalue and rvalue of union type.

# This maps an expression to a list of bound types for every item in the union type.

type_assignments: Assigns | None = None

def __init__(self, options: Options) -> None:

# Each frame gets an increasing, distinct id.

self.next_id = 1

# The stack of frames currently used. These map

# literal_hash(expr) -- literals like 'foo.bar' --

# to types. The last element of this list is the

# top-most, current frame. Each earlier element

# records the state as of when that frame was last

# on top of the stack.

self.frames = [Frame(self._get_id())]

# For frames higher in the stack, we record the set of

# Frames that can escape there, either by falling off

# the end of the frame or by a loop control construct

# or raised exception. The last element of self.frames

# has no corresponding element in this list.

self.options_on_return: list[list[Frame]] = []

# Maps literal_hash(expr) to get_declaration(expr)

# for every expr stored in the binder

self.declarations: dict[Key, Type | None] = {}

# Set of other keys to invalidate if a key is changed, e.g. x -> {x.a, x[0]}

# Whenever a new key (e.g. x.a.b) is added, we update this

self.dependencies: dict[Key, set[Key]] = {}

# Whether the last pop changed the newly top frame on exit

self.last_pop_changed = False

# These are used to track control flow in try statements and loops.

self.try_frames: set[int] = set()

self.break_frames: list[int] = []

self.continue_frames: list[int] = []

# If True, initial assignment to a simple variable (e.g. "x", but not "x.y")

# is added to the binder. This allows more precise narrowing and more

# flexible inference of variable types (--allow-redefinition).

self.bind_all = options.allow_redefinition

# This tracks any externally visible changes in binder to invalidate

# expression caches when needed.

self.version = 0

def _get_id(self) -> int:

self.next_id += 1

return self.next_id

def _add_dependencies(self, key: Key, value: Key | None = None) -> None:

if value is None:

value = key

else:

self.dependencies.setdefault(key, set()).add(value)

for elt in subkeys(key):

self._add_dependencies(elt, value)

def push_frame(self, conditional_frame: bool = False) -> Frame:

"""Push a new frame into the binder."""

f = Frame(self._get_id(), conditional_frame)

self.frames.append(f)

self.options_on_return.append([])

return f

def _put(self, key: Key, type: Type, from_assignment: bool, index: int = -1) -> None:

self.version += 1

self.frames[index].types[key] = CurrentType(type, from_assignment)

def _get(self, key: Key, index: int = -1) -> CurrentType | None:

if index < 0:

index += len(self.frames)

for i in range(index, -1, -1):

if key in self.frames[i].types:

return self.frames[i].types[key]

return None

@classmethod

def can_put_directly(cls, expr: Expression) -> bool:

"""Will `.put()` on this expression be successful?

This is inlined in `.put()` because the logic is rather hot and must be kept

in sync.

"""

return isinstance(expr, (IndexExpr, MemberExpr, NameExpr)) and literal(expr) > LITERAL_NO

def put(self, expr: Expression, typ: Type, *, from_assignment: bool = True) -> None:

"""Directly set the narrowed type of expression (if it supports it).

This is used for isinstance() etc. Assignments should go through assign_type().

"""

if not isinstance(expr, (IndexExpr, MemberExpr, NameExpr)):

return

if not literal(expr):

return

key = literal_hash(expr)

assert key is not None, "Internal error: binder tried to put non-literal"

if key not in self.declarations:

self.declarations[key] = get_declaration(expr)

self._add_dependencies(key)

self._put(key, typ, from_assignment)

def unreachable(self) -> None:

self.version += 1

self.frames[-1].unreachable = True

def suppress_unreachable_warnings(self) -> None:

self.frames[-1].suppress_unreachable_warnings = True

def get(self, expr: Expression) -> Type | None:

key = literal_hash(expr)

assert key is not None, "Internal error: binder tried to get non-literal"

found = self._get(key)

if found is None:

return None

return found.type

def is_unreachable(self) -> bool:

# TODO: Copy the value of unreachable into new frames to avoid

# this traversal on every statement?

return any(f.unreachable for f in self.frames)

def is_unreachable_warning_suppressed(self) -> bool:

return any(f.suppress_unreachable_warnings for f in self.frames)

def cleanse(self, expr: Expression) -> None:

"""Remove all references to a Node from the binder."""

key = literal_hash(expr)

assert key is not None, "Internal error: binder tried cleanse non-literal"

self._cleanse_key(key)

def _cleanse_key(self, key: Key) -> None:

"""Remove all references to a key from the binder."""

for frame in self.frames:

if key in frame.types:

del frame.types[key]

def update_from_options(self, frames: list[Frame]) -> bool:

"""Update the frame to reflect that each key will be updated

as in one of the frames. Return whether any item changes.

If a key is declared as AnyType, only update it if all the

options are the same.

"""

all_reachable = all(not f.unreachable for f in frames)

if not all_reachable:

frames = [f for f in frames if not f.unreachable]

changed = False

keys = [key for f in frames for key in f.types]

if len(keys) > 1:

keys = list(set(keys))

for key in keys:

current_value = self._get(key)

resulting_values = [f.types.get(key, current_value) for f in frames]

# Keys can be narrowed using two different semantics. The new semantics

# is enabled for inferred variables when bind_all is true, and it allows

# variable types to be widened using subsequent assignments. This is

# not allowed for instance attributes and annotated variables.

var = extract_var_from_literal_hash(key)

old_semantics = (

not self.bind_all or var is None or not var.is_inferred and not var.is_argument

)

if old_semantics and any(x is None for x in resulting_values):

# We didn't know anything about key before

# (current_value must be None), and we still don't

# know anything about key in at least one possible frame.

continue

resulting_values = [x for x in resulting_values if x is not None]

if all_reachable and all(not x.from_assignment for x in resulting_values):

# Do not synthesize a new type if we encountered a conditional block

# (if, while or match-case) without assignments.

# See check-isinstance.test::testNoneCheckDoesNotMakeTypeVarOptional

# This is a safe assumption: the fact that we checked something with `is`

# or `isinstance` does not change the type of the value.

continue

# Remove exact duplicates to save pointless work later, this is

# a micro-optimization for --allow-redefinition.

seen_types = set()

resulting_types = []

for rv in resulting_values:

assert rv is not None

if rv.type in seen_types:

continue

resulting_types.append(rv.type)

seen_types.add(rv.type)

type = resulting_types[0]

declaration_type = get_proper_type(self.declarations.get(key))

if isinstance(declaration_type, AnyType):

# At this point resulting values can't contain None, see continue above

if not all(is_same_type(type, t) for t in resulting_types[1:]):

type = AnyType(TypeOfAny.from_another_any, source_any=declaration_type)

else:

possible_types = []

for t in resulting_types:

assert t is not None

possible_types.append(t)

if len(possible_types) == 1:

# This is to avoid calling get_proper_type() unless needed, as this may

# interfere with our (hacky) TypeGuard support.

type = possible_types[0]

else:

type = make_simplified_union(possible_types)

# Legacy guard for corner case when the original type is TypeVarType.

if isinstance(declaration_type, TypeVarType) and not is_subtype(

type, declaration_type

):

type = declaration_type

# Try simplifying resulting type for unions involving variadic tuples.

# Technically, everything is still valid without this step, but if we do

# not do this, this may create long unions after exiting an if check like:

# x: tuple[int, ...]

# if len(x) < 10:

# ...

# We want the type of x to be tuple[int, ...] after this block (if it is

# still equivalent to such type).

if isinstance(type, UnionType):

type = collapse_variadic_union(type)

if (

old_semantics

and isinstance(type, ProperType)

and isinstance(type, UnionType)

):

# Simplify away any extra Any's that were added to the declared

# type when popping a frame.

simplified = UnionType.make_union(

[t for t in type.items if not isinstance(get_proper_type(t), AnyType)]

)

if simplified == self.declarations[key]:

type = simplified

if (

current_value is None

or not is_same_type(type, current_value.type)

# Manually carry over any narrowing from hasattr() from inner frames. This is

# a bit ad-hoc, but our handling of hasattr() is on best effort basis anyway.

or isinstance(p_type := get_proper_type(type), Instance)

and p_type.extra_attrs

):

self._put(key, type, from_assignment=True)

if current_value is not None or extract_var_from_literal_hash(key) is None:

# We definitely learned something new

changed = True

elif not changed:

# If there is no current value compare with the declaration. This prevents

# reporting false changes in cases like this:

# x: int

# if foo():

# x = 1

# else:

# x = 2

# We check partial types and widening in accept_loop() separately, so

# this should be safe.

changed = declaration_type is not None and not is_same_type(

type, declaration_type

)

self.frames[-1].unreachable = not frames

return changed

def pop_frame(self, can_skip: bool, fall_through: int, *, discard: bool = False) -> Frame:

"""Pop a frame and return it.

See frame_context() for documentation of fall_through and discard.

"""

if fall_through > 0:

self.allow_jump(-fall_through)

result = self.frames.pop()

options = self.options_on_return.pop()

if discard:

self.last_pop_changed = False

return result

if can_skip:

options.insert(0, self.frames[-1])

self.last_pop_changed = self.update_from_options(options)

return result

@contextmanager

def accumulate_type_assignments(self) -> Iterator[Assigns]:

"""Push a new map to collect assigned types in multiassign from union.

If this map is not None, actual binding is deferred until all items in

the union are processed (a union of collected items is later bound

manually by the caller).

"""

old_assignments = None

if self.type_assignments is not None:

old_assignments = self.type_assignments

self.type_assignments = defaultdict(list)

yield self.type_assignments

self.type_assignments = old_assignments

def assign_type(self, expr: Expression, type: Type, declared_type: Type | None) -> None:

"""Narrow type of expression through an assignment.

Do nothing if the expression doesn't support narrowing.

When not narrowing though an assignment (isinstance() etc.), use put()

directly. This omits some special-casing logic for assignments.

"""

# We should erase last known value in binder, because if we are using it,

# it means that the target is not final, and therefore can't hold a literal.

type = remove_instance_last_known_values(type)

if self.type_assignments is not None:

# We are in a multiassign from union, defer the actual binding,

# just collect the types.

self.type_assignments[expr].append((type, declared_type))

return

if not isinstance(expr, (IndexExpr, MemberExpr, NameExpr)):

return

if not literal(expr):

return

self.invalidate_dependencies(expr)

if declared_type is None:

# Not sure why this happens. It seems to mainly happen in

# member initialization.

return

if not is_subtype(type, declared_type):

# Pretty sure this is only happens when there's a type error.

# Ideally this function wouldn't be called if the

# expression has a type error, though -- do other kinds of

# errors cause this function to get called at invalid

# times?

return

p_declared = get_proper_type(declared_type)

p_type = get_proper_type(type)

if isinstance(p_type, AnyType):

# Any type requires some special casing, for both historical reasons,

# and to optimise user experience without sacrificing correctness too much.

if isinstance(expr, RefExpr) and isinstance(expr.node, Var) and expr.node.is_inferred:

# First case: a local/global variable without explicit annotation,

# in this case we just assign Any (essentially following the SSA logic).

self.put(expr, type)

elif isinstance(p_declared, UnionType):

all_items = flatten_nested_unions(p_declared.items)

if any(isinstance(get_proper_type(item), NoneType) for item in all_items):

# Second case: explicit optional type, in this case we optimize for

# a common pattern when an untyped value used as a fallback replacing None.

new_items = [

type if isinstance(get_proper_type(item), NoneType) else item

for item in all_items

]

self.put(expr, UnionType(new_items))

elif any(isinstance(get_proper_type(item), AnyType) for item in all_items):

# Third case: a union already containing Any (most likely from

# an un-imported name), in this case we allow assigning Any as well.

self.put(expr, type)

else:

# In all other cases we don't narrow to Any to minimize false negatives.

self.put(expr, declared_type)

else:

self.put(expr, declared_type)

elif isinstance(p_declared, AnyType):

# Mirroring the first case above, we don't narrow to a precise type if the variable

# has an explicit `Any` type annotation.

if isinstance(expr, RefExpr) and isinstance(expr.node, Var) and expr.node.is_inferred:

self.put(expr, type)

else:

self.put(expr, declared_type)

else:

self.put(expr, type)

for i in self.try_frames:

# XXX This should probably not copy the entire frame, but

# just copy this variable into a single stored frame.

self.allow_jump(i)

def invalidate_dependencies(self, expr: BindableExpression) -> None:

"""Invalidate knowledge of types that include expr, but not expr itself.

For example, when expr is foo.bar, invalidate foo.bar.baz.

It is overly conservative: it invalidates globally, including

in code paths unreachable from here.

"""

key = literal_hash(expr)

assert key is not None

for dep in self.dependencies.get(key, set()):

self._cleanse_key(dep)

def allow_jump(self, index: int) -> None:

# self.frames and self.options_on_return have different lengths

# so make sure the index is positive

if index < 0:

index += len(self.options_on_return)

frame = Frame(self._get_id())

for f in self.frames[index + 1 :]:

frame.types.update(f.types)

if f.unreachable:

frame.unreachable = True

self.options_on_return[index].append(frame)

def handle_break(self) -> None:

self.allow_jump(self.break_frames[-1])

self.unreachable()

def handle_continue(self) -> None:

self.allow_jump(self.continue_frames[-1])

self.unreachable()

def frame_context(

self,

*,

can_skip: bool,

fall_through: int = 1,

break_frame: int = 0,

continue_frame: int = 0,

conditional_frame: bool = False,

try_frame: bool = False,

discard: bool = False,

) -> FrameContext:

"""Return a context manager that pushes/pops frames on enter/exit.

If can_skip is True, control flow is allowed to bypass the

newly-created frame.

If fall_through > 0, then it will allow control flow that

falls off the end of the frame to escape to its ancestor

`fall_through` levels higher. Otherwise, control flow ends

at the end of the frame.

If break_frame > 0, then 'break' statements within this frame

will jump out to the frame break_frame levels higher than the

frame created by this call to frame_context. Similarly, for

continue_frame and 'continue' statements.

If try_frame is true, then execution is allowed to jump at any

point within the newly created frame (or its descendants) to

its parent (i.e., to the frame that was on top before this

call to frame_context).

If discard is True, then this is a temporary throw-away frame

(used e.g. for isolation) and its effect will be discarded on pop.

After the context manager exits, self.last_pop_changed indicates

whether any types changed in the newly-topmost frame as a result

of popping this frame.

"""

return FrameContext(

self,

can_skip=can_skip,

fall_through=fall_through,

break_frame=break_frame,

continue_frame=continue_frame,

conditional_frame=conditional_frame,

try_frame=try_frame,

discard=discard,

)

@contextmanager

def top_frame_context(self) -> Iterator[Frame]:

"""A variant of frame_context for use at the top level of

a namespace (module, function, or class).

"""

assert len(self.frames) == 1

yield self.push_frame()

self.pop_frame(True, 0)

assert len(self.frames) == 1

def get_declaration(expr: BindableExpression) -> Type | None:

"""Get the declared or inferred type of a RefExpr expression.

Return None if there is no type or the expression is not a RefExpr.

This can return None if the type hasn't been inferred yet.

"""

if isinstance(expr, RefExpr):

if isinstance(expr.node, Var):

type = expr.node.type

if not isinstance(get_proper_type(type), PartialType):

return type

elif isinstance(expr.node, TypeInfo):

return TypeType(fill_typevars_with_any(expr.node))

return None

def collapse_variadic_union(typ: UnionType) -> Type:

"""Simplify a union involving variadic tuple if possible.

This will collapse a type like e.g.

tuple[X, Z] | tuple[X, Y, Z] | tuple[X, Y, Y, *tuple[Y, ...], Z]

back to

tuple[X, *tuple[Y, ...], Z]

which is equivalent, but much simpler form of the same type.

"""

tuple_items = []

other_items = []

for t in typ.items:

p_t = get_proper_type(t)

if isinstance(p_t, TupleType):

tuple_items.append(p_t)

else:

other_items.append(t)

if len(tuple_items) <= 1:

# This type cannot be simplified further.

return typ

tuple_items = sorted(tuple_items, key=lambda t: len(t.items))

first = tuple_items[0]

last = tuple_items[-1]

unpack_index = find_unpack_in_list(last.items)

if unpack_index is None:

return typ

unpack = last.items[unpack_index]

assert isinstance(unpack, UnpackType)

unpacked = get_proper_type(unpack.type)

if not isinstance(unpacked, Instance):

return typ

assert unpacked.type.fullname == "builtins.tuple"

suffix = last.items[unpack_index + 1 :]

# Check that first item matches the expected pattern and infer prefix.

if len(first.items) < len(suffix):

return typ

if suffix and first.items[-len(suffix) :] != suffix:

return typ

if suffix:

prefix = first.items[: -len(suffix)]

else:

prefix = first.items

# Check that all middle types match the expected pattern as well.

arg = unpacked.args[0]

for i, it in enumerate(tuple_items[1:-1]):

if it.items != prefix + [arg] * (i + 1) + suffix:

return typ

# Check the last item (the one with unpack), and choose an appropriate simplified type.

if last.items != prefix + [arg] * (len(typ.items) - 1) + [unpack] + suffix:

return typ

if len(first.items) == 0:

simplified: Type = unpacked.copy_modified()

else:

simplified = TupleType(prefix + [unpack] + suffix, fallback=last.partial_fallback)

return UnionType.make_union([simplified] + other_items)