mypy/server/deps.py

"""Generate fine-grained dependencies for AST nodes, for use in the daemon mode.

Dependencies are stored in a map from *triggers* to *sets of affected locations*.

A trigger is a string that represents a program property that has changed, such
as the signature of a specific function. Triggers are written as '<...>' (angle
brackets). When a program property changes, we determine the relevant trigger(s)
and all affected locations. The latter are stale and will have to be reprocessed.

An affected location is a string than can refer to a *target* (a non-nested
function or method, or a module top level), a class, or a trigger (for
recursively triggering other triggers).

Here's an example representation of a simple dependency map (in format
"<trigger> -> locations"):

  <m.A.g> -> m.f
  <m.A> -> <m.f>, m.A, m.f

Assuming 'A' is a class, this means that

1) if a property of 'm.A.g', such as the signature, is changed, we need
   to process target (function) 'm.f'

2) if the MRO or other significant property of class 'm.A' changes, we
   need to process target 'm.f', the entire class 'm.A', and locations
   triggered by trigger '<m.f>' (this explanation is a bit simplified;
   see below for more details).

The triggers to fire are determined using mypy.server.astdiff.

Examples of triggers:

* '<mod.x>' represents a module attribute/function/class. If any externally
  visible property of 'x' changes, this gets fired. For changes within
  classes, only "big" changes cause the class to be triggered (such as a
  change in MRO). Smaller changes, such as changes to some attributes, don't
  trigger the entire class.
* '<mod.Cls.x>' represents the type and kind of attribute/method 'x' of
  class 'mod.Cls'. This can also refer to an attribute inherited from a
  base class (relevant if it's accessed through a value of type 'Cls'
  instead of the base class type).
* '<package.mod>' represents the existence of module 'package.mod'. This
  gets triggered if 'package.mod' is created or deleted, or if it gets
  changed into something other than a module.

Examples of locations:

* 'mod' is the top level of module 'mod' (doesn't include any function bodies,
  but includes class bodies not nested within a function).
* 'mod.f' is function 'f' in module 'mod' (module-level variables aren't separate
  locations but are included in the module top level). Functions also include
  any nested functions and classes -- such nested definitions aren't separate
  locations, for simplicity of implementation.
* 'mod.Cls.f' is method 'f' of 'mod.Cls'. Non-method attributes aren't locations.
* 'mod.Cls' represents each method in class 'mod.Cls' + the top-level of the
  module 'mod'. (To simplify the implementation, there is no location that only
  includes the body of a class without the entire surrounding module top level.)
* Trigger '<...>' as a location is an indirect way of referring to to all
  locations triggered by the trigger. These indirect locations keep the
  dependency map smaller and easier to manage.

Triggers can be triggered by program changes such as these:

* Addition or deletion of an attribute (or module).
* Change of the kind of thing a name represents (such as a change from a function
  to a class).
* Change of the static type of a name.

Changes in the body of a function that aren't reflected in the signature don't
cause the function to be triggered. More generally, we trigger only on changes
that may affect type checking results outside the module that contains the
change.

We don't generate dependencies from builtins and certain other stdlib modules,
since these change very rarely, and they would just increase the size of the
dependency map significantly without significant benefit.

Test cases for this module live in 'test-data/unit/deps*.test'.
"""

from typing import Dict, List, Set, Optional, Tuple
from typing_extensions import DefaultDict

from mypy.checkmember import bind_self
from mypy.nodes import (
    Node, Expression, MypyFile, FuncDef, ClassDef, AssignmentStmt, NameExpr, MemberExpr, Import,
    ImportFrom, CallExpr, CastExpr, TypeVarExpr, TypeApplication, IndexExpr, UnaryExpr, OpExpr,
    ComparisonExpr, GeneratorExpr, DictionaryComprehension, StarExpr, PrintStmt, ForStmt, WithStmt,
    TupleExpr, OperatorAssignmentStmt, DelStmt, YieldFromExpr, Decorator, Block,
    TypeInfo, FuncBase, OverloadedFuncDef, RefExpr, SuperExpr, Var, NamedTupleExpr, TypedDictExpr,
    LDEF, MDEF, GDEF, TypeAliasExpr, NewTypeExpr, ImportAll, EnumCallExpr, AwaitExpr
)
from mypy.operators import (
    op_methods, reverse_op_methods, ops_with_inplace_method, unary_op_methods
)
from mypy.traverser import TraverserVisitor
from mypy.types import (
    Type, Instance, AnyType, NoneType, TypeVisitor, CallableType, DeletedType, PartialType,
    TupleType, TypeType, TypeVarType, TypedDictType, UnboundType, UninhabitedType, UnionType,
    FunctionLike, Overloaded, TypeOfAny, LiteralType, ErasedType, get_proper_type, ProperType,
    TypeAliasType, ParamSpecType, UnpackType
)
from mypy.server.trigger import make_trigger, make_wildcard_trigger
from mypy.util import correct_relative_import
from mypy.scope import Scope
from mypy.typestate import TypeState
from mypy.options import Options


def get_dependencies(target: MypyFile,
                     type_map: Dict[Expression, Type],
                     python_version: Tuple[int, int],
                     options: Options) -> Dict[str, Set[str]]:
    """Get all dependencies of a node, recursively."""
    visitor = DependencyVisitor(type_map, python_version, target.alias_deps, options)
    target.accept(visitor)
    return visitor.map


def get_dependencies_of_target(module_id: str,
                               module_tree: MypyFile,
                               target: Node,
                               type_map: Dict[Expression, Type],
                               python_version: Tuple[int, int]) -> Dict[str, Set[str]]:
    """Get dependencies of a target -- don't recursive into nested targets."""
    # TODO: Add tests for this function.
    visitor = DependencyVisitor(type_map, python_version, module_tree.alias_deps)
    with visitor.scope.module_scope(module_id):
        if isinstance(target, MypyFile):
            # Only get dependencies of the top-level of the module. Don't recurse into
            # functions.
            for defn in target.defs:
                # TODO: Recurse into top-level statements and class bodies but skip functions.
                if not isinstance(defn, (ClassDef, Decorator, FuncDef, OverloadedFuncDef)):
                    defn.accept(visitor)
        elif isinstance(target, FuncBase) and target.info:
            # It's a method.
            # TODO: Methods in nested classes.
            with visitor.scope.class_scope(target.info):
                target.accept(visitor)
        else:
            target.accept(visitor)
    return visitor.map


class DependencyVisitor(TraverserVisitor):
    def __init__(self,
                 type_map: Dict[Expression, Type],
                 python_version: Tuple[int, int],
                 alias_deps: 'DefaultDict[str, Set[str]]',
                 options: Optional[Options] = None) -> None:
        self.scope = Scope()
        self.type_map = type_map
        self.python2 = python_version[0] == 2
        # This attribute holds a mapping from target to names of type aliases
        # it depends on. These need to be processed specially, since they are
        # only present in expanded form in symbol tables. For example, after:
        #    A = List[int]
        #    x: A
        # The module symbol table will just have a Var `x` with type `List[int]`,
        # and the dependency of `x` on `A` is lost. Therefore the alias dependencies
        # are preserved at alias expansion points in `semanal.py`, stored as an attribute
        # on MypyFile, and then passed here.
        self.alias_deps = alias_deps
        self.map: Dict[str, Set[str]] = {}
        self.is_class = False
        self.is_package_init_file = False
        self.options = options

    def visit_mypy_file(self, o: MypyFile) -> None:
        with self.scope.module_scope(o.fullname):
            self.is_package_init_file = o.is_package_init_file()
            self.add_type_alias_deps(self.scope.current_target())
            for trigger, targets in o.plugin_deps.items():
                self.map.setdefault(trigger, set()).update(targets)
            super().visit_mypy_file(o)

    def visit_func_def(self, o: FuncDef) -> None:
        with self.scope.function_scope(o):
            target = self.scope.current_target()
            if o.type:
                if self.is_class and isinstance(o.type, FunctionLike):
                    signature: Type = bind_self(o.type)
                else:
                    signature = o.type
                for trigger in self.get_type_triggers(signature):
                    self.add_dependency(trigger)
                    self.add_dependency(trigger, target=make_trigger(target))
            if o.info:
                for base in non_trivial_bases(o.info):
                    # Base class __init__/__new__ doesn't generate a logical
                    # dependency since the override can be incompatible.
                    if not self.use_logical_deps() or o.name not in ('__init__', '__new__'):
                        self.add_dependency(make_trigger(base.fullname + '.' + o.name))
            self.add_type_alias_deps(self.scope.current_target())
            super().visit_func_def(o)
            variants = set(o.expanded) - {o}
            for ex in variants:
                if isinstance(ex, FuncDef):
                    super().visit_func_def(ex)

    def visit_decorator(self, o: Decorator) -> None:
        if not self.use_logical_deps():
            # We don't need to recheck outer scope for an overload, only overload itself.
            # Also if any decorator is nested, it is not externally visible, so we don't need to
            # generate dependency.
            if not o.func.is_overload and self.scope.current_function_name() is None:
                self.add_dependency(make_trigger(o.func.fullname))
        else:
            # Add logical dependencies from decorators to the function. For example,
            # if we have
            #     @dec
            #     def func(): ...
            # then if `dec` is unannotated, then it will "spoil" `func` and consequently
            # all call sites, making them all `Any`.
            for d in o.decorators:
                tname: Optional[str] = None
                if isinstance(d, RefExpr) and d.fullname is not None:
                    tname = d.fullname
                if (isinstance(d, CallExpr) and isinstance(d.callee, RefExpr) and
                        d.callee.fullname is not None):
                    tname = d.callee.fullname
                if tname is not None:
                    self.add_dependency(make_trigger(tname), make_trigger(o.func.fullname))
        super().visit_decorator(o)

    def visit_class_def(self, o: ClassDef) -> None:
        with self.scope.class_scope(o.info):
            target = self.scope.current_full_target()
            self.add_dependency(make_trigger(target), target)
            old_is_class = self.is_class
            self.is_class = True
            # Add dependencies to type variables of a generic class.
            for tv in o.type_vars:
                self.add_dependency(make_trigger(tv.fullname), target)
            self.process_type_info(o.info)
            super().visit_class_def(o)
            self.is_class = old_is_class

    def visit_newtype_expr(self, o: NewTypeExpr) -> None:
        if o.info:
            with self.scope.class_scope(o.info):
                self.process_type_info(o.info)

    def process_type_info(self, info: TypeInfo) -> None:
        target = self.scope.current_full_target()
        for base in info.bases:
            self.add_type_dependencies(base, target=target)
        if info.tuple_type:
            self.add_type_dependencies(info.tuple_type, target=make_trigger(target))
        if info.typeddict_type:
            self.add_type_dependencies(info.typeddict_type, target=make_trigger(target))
        if info.declared_metaclass:
            self.add_type_dependencies(info.declared_metaclass, target=make_trigger(target))
        if info.is_protocol:
            for base_info in info.mro[:-1]:
                # We add dependencies from whole MRO to cover explicit subprotocols.
                # For example:
                #
                #     class Super(Protocol):
                #         x: int
                #     class Sub(Super, Protocol):
                #         y: int
                #
                # In this example we add <Super[wildcard]> -> <Sub>, to invalidate Sub if
                # a new member is added to Super.
                self.add_dependency(make_wildcard_trigger(base_info.fullname),
                                    target=make_trigger(target))
                # More protocol dependencies are collected in TypeState._snapshot_protocol_deps
                # after a full run or update is finished.

        self.add_type_alias_deps(self.scope.current_target())
        for name, node in info.names.items():
            if isinstance(node.node, Var):
                # Recheck Liskov if needed, self definitions are checked in the defining method
                if node.node.is_initialized_in_class and has_user_bases(info):
                    self.add_dependency(make_trigger(info.fullname + '.' + name))
                for base_info in non_trivial_bases(info):
                    # If the type of an attribute changes in a base class, we make references
                    # to the attribute in the subclass stale.
                    self.add_dependency(make_trigger(base_info.fullname + '.' + name),
                                        target=make_trigger(info.fullname + '.' + name))
        for base_info in non_trivial_bases(info):
            for name, node in base_info.names.items():
                if self.use_logical_deps():
                    # Skip logical dependency if an attribute is not overridden. For example,
                    # in case of:
                    #     class Base:
                    #         x = 1
                    #         y = 2
                    #     class Sub(Base):
                    #         x = 3
                    # we skip <Base.y> -> <Child.y>, because even if `y` is unannotated it
                    # doesn't affect precision of Liskov checking.
                    if name not in info.names:
                        continue
                    # __init__ and __new__ can be overridden with different signatures, so no
                    # logical dependency.
                    if name in ('__init__', '__new__'):
                        continue
                self.add_dependency(make_trigger(base_info.fullname + '.' + name),
                                    target=make_trigger(info.fullname + '.' + name))
            if not self.use_logical_deps():
                # These dependencies are only useful for propagating changes --
                # they aren't logical dependencies since __init__ and __new__ can be
                # overridden with a different signature.
                self.add_dependency(make_trigger(base_info.fullname + '.__init__'),
                                    target=make_trigger(info.fullname + '.__init__'))
                self.add_dependency(make_trigger(base_info.fullname + '.__new__'),
                                    target=make_trigger(info.fullname + '.__new__'))
                # If the set of abstract attributes change, this may invalidate class
                # instantiation, or change the generated error message, since Python checks
                # class abstract status when creating an instance.
                self.add_dependency(make_trigger(base_info.fullname + '.(abstract)'),
                                    target=make_trigger(info.fullname + '.__init__'))
                # If the base class abstract attributes change, subclass abstract
                # attributes need to be recalculated.
                self.add_dependency(make_trigger(base_info.fullname + '.(abstract)'))

    def visit_import(self, o: Import) -> None:
        for id, as_id in o.ids:
            self.add_dependency(make_trigger(id), self.scope.current_target())

    def visit_import_from(self, o: ImportFrom) -> None:
        if self.use_logical_deps():
            # Just importing a name doesn't create a logical dependency.
            return
        module_id, _ = correct_relative_import(self.scope.current_module_id(),
                                               o.relative,
                                               o.id,
                                               self.is_package_init_file)
        self.add_dependency(make_trigger(module_id))  # needed if module is added/removed
        for name, as_name in o.names:
            self.add_dependency(make_trigger(module_id + '.' + name))

    def visit_import_all(self, o: ImportAll) -> None:
        module_id, _ = correct_relative_import(self.scope.current_module_id(),
                                               o.relative,
                                               o.id,
                                               self.is_package_init_file)
        # The current target needs to be rechecked if anything "significant" changes in the
        # target module namespace (as the imported definitions will need to be updated).
        self.add_dependency(make_wildcard_trigger(module_id))

    def visit_block(self, o: Block) -> None:
        if not o.is_unreachable:
            super().visit_block(o)

    def visit_assignment_stmt(self, o: AssignmentStmt) -> None:
        rvalue = o.rvalue
        if isinstance(rvalue, CallExpr) and isinstance(rvalue.analyzed, TypeVarExpr):
            analyzed = rvalue.analyzed
            self.add_type_dependencies(analyzed.upper_bound,
                                       target=make_trigger(analyzed.fullname))
            for val in analyzed.values:
                self.add_type_dependencies(val, target=make_trigger(analyzed.fullname))
            # We need to re-analyze the definition if bound or value is deleted.
            super().visit_call_expr(rvalue)
        elif isinstance(rvalue, CallExpr) and isinstance(rvalue.analyzed, NamedTupleExpr):
            # Depend on types of named tuple items.
            info = rvalue.analyzed.info
            prefix = '%s.%s' % (self.scope.current_full_target(), info.name)
            for name, symnode in info.names.items():
                if not name.startswith('_') and isinstance(symnode.node, Var):
                    typ = symnode.node.type
                    if typ:
                        self.add_type_dependencies(typ)
                        self.add_type_dependencies(typ, target=make_trigger(prefix))
                        attr_target = make_trigger('%s.%s' % (prefix, name))
                        self.add_type_dependencies(typ, target=attr_target)
        elif isinstance(rvalue, CallExpr) and isinstance(rvalue.analyzed, TypedDictExpr):
            # Depend on the underlying typeddict type
            info = rvalue.analyzed.info
            assert info.typeddict_type is not None
            prefix = '%s.%s' % (self.scope.current_full_target(), info.name)
            self.add_type_dependencies(info.typeddict_type, target=make_trigger(prefix))
        elif isinstance(rvalue, CallExpr) and isinstance(rvalue.analyzed, EnumCallExpr):
            # Enum values are currently not checked, but for future we add the deps on them
            for name, symnode in rvalue.analyzed.info.names.items():
                if isinstance(symnode.node, Var) and symnode.node.type:
                    self.add_type_dependencies(symnode.node.type)
        elif o.is_alias_def:
            assert len(o.lvalues) == 1
            lvalue = o.lvalues[0]
            assert isinstance(lvalue, NameExpr)
            typ = get_proper_type(self.type_map.get(lvalue))
            if isinstance(typ, FunctionLike) and typ.is_type_obj():
                class_name = typ.type_object().fullname
                self.add_dependency(make_trigger(class_name + '.__init__'))
                self.add_dependency(make_trigger(class_name + '.__new__'))
            if isinstance(rvalue, IndexExpr) and isinstance(rvalue.analyzed, TypeAliasExpr):
                self.add_type_dependencies(rvalue.analyzed.type)
            elif typ:
                self.add_type_dependencies(typ)
        else:
            # Normal assignment
            super().visit_assignment_stmt(o)
            for lvalue in o.lvalues:
                self.process_lvalue(lvalue)
            items = o.lvalues + [rvalue]
            for i in range(len(items) - 1):
                lvalue = items[i]
                rvalue = items[i + 1]
                if isinstance(lvalue, TupleExpr):
                    self.add_attribute_dependency_for_expr(rvalue, '__iter__')
            if o.type:
                self.add_type_dependencies(o.type)
        if self.use_logical_deps() and o.unanalyzed_type is None:
            # Special case: for definitions without an explicit type like this:
            #     x = func(...)
            # we add a logical dependency <func> -> <x>, because if `func` is not annotated,
            # then it will make all points of use of `x` unchecked.
            if (isinstance(rvalue, CallExpr) and isinstance(rvalue.callee, RefExpr)
                    and rvalue.callee.fullname is not None):
                fname: Optional[str] = None
                if isinstance(rvalue.callee.node, TypeInfo):
                    # use actual __init__ as a dependency source
                    init = rvalue.callee.node.get('__init__')
                    if init and isinstance(init.node, FuncBase):
                        fname = init.node.fullname
                else:
                    fname = rvalue.callee.fullname
                if fname is None:
                    return
                for lv in o.lvalues:
                    if isinstance(lv, RefExpr) and lv.fullname and lv.is_new_def:
                        if lv.kind == LDEF:
                            return  # local definitions don't generate logical deps
                        self.add_dependency(make_trigger(fname), make_trigger(lv.fullname))

    def process_lvalue(self, lvalue: Expression) -> None:
        """Generate additional dependencies for an lvalue."""
        if isinstance(lvalue, IndexExpr):
            self.add_operator_method_dependency(lvalue.base, '__setitem__')
        elif isinstance(lvalue, NameExpr):
            if lvalue.kind in (MDEF, GDEF):
                # Assignment to an attribute in the class body, or direct assignment to a
                # global variable.
                lvalue_type = self.get_non_partial_lvalue_type(lvalue)
                type_triggers = self.get_type_triggers(lvalue_type)
                attr_trigger = make_trigger('%s.%s' % (self.scope.current_full_target(),
                                                       lvalue.name))
                for type_trigger in type_triggers:
                    self.add_dependency(type_trigger, attr_trigger)
        elif isinstance(lvalue, MemberExpr):
            if self.is_self_member_ref(lvalue) and lvalue.is_new_def:
                node = lvalue.node
                if isinstance(node, Var):
                    info = node.info
                    if info and has_user_bases(info):
                        # Recheck Liskov for self definitions
                        self.add_dependency(make_trigger(info.fullname + '.' + lvalue.name))
            if lvalue.kind is None:
                # Reference to a non-module attribute
                if lvalue.expr not in self.type_map:
                    # Unreachable assignment -> not checked so no dependencies to generate.
                    return
                object_type = self.type_map[lvalue.expr]
                lvalue_type = self.get_non_partial_lvalue_type(lvalue)
                type_triggers = self.get_type_triggers(lvalue_type)
                for attr_trigger in self.attribute_triggers(object_type, lvalue.name):
                    for type_trigger in type_triggers:
                        self.add_dependency(type_trigger, attr_trigger)
        elif isinstance(lvalue, TupleExpr):
            for item in lvalue.items:
                self.process_lvalue(item)
        elif isinstance(lvalue, StarExpr):
            self.process_lvalue(lvalue.expr)

    def is_self_member_ref(self, memberexpr: MemberExpr) -> bool:
        """Does memberexpr to refer to an attribute of self?"""
        if not isinstance(memberexpr.expr, NameExpr):
            return False
        node = memberexpr.expr.node
        return isinstance(node, Var) and node.is_self

    def get_non_partial_lvalue_type(self, lvalue: RefExpr) -> Type:
        if lvalue not in self.type_map:
            # Likely a block considered unreachable during type checking.
            return UninhabitedType()
        lvalue_type = get_proper_type(self.type_map[lvalue])
        if isinstance(lvalue_type, PartialType):
            if isinstance(lvalue.node, Var):
                if lvalue.node.type:
                    lvalue_type = get_proper_type(lvalue.node.type)
                else:
                    lvalue_type = UninhabitedType()
            else:
                # Probably a secondary, non-definition assignment that doesn't
                # result in a non-partial type. We won't be able to infer any
                # dependencies from this so just return something. (The first,
                # definition assignment with a partial type is handled
                # differently, in the semantic analyzer.)
                assert not lvalue.is_new_def
                return UninhabitedType()
        return lvalue_type

    def visit_operator_assignment_stmt(self, o: OperatorAssignmentStmt) -> None:
        super().visit_operator_assignment_stmt(o)
        self.process_lvalue(o.lvalue)
        method = op_methods[o.op]
        self.add_attribute_dependency_for_expr(o.lvalue, method)
        if o.op in ops_with_inplace_method:
            inplace_method = '__i' + method[2:]
            self.add_attribute_dependency_for_expr(o.lvalue, inplace_method)

    def visit_for_stmt(self, o: ForStmt) -> None:
        super().visit_for_stmt(o)
        if not o.is_async:
            # __getitem__ is only used if __iter__ is missing but for simplicity we
            # just always depend on both.
            self.add_attribute_dependency_for_expr(o.expr, '__iter__')
            self.add_attribute_dependency_for_expr(o.expr, '__getitem__')
            if o.inferred_iterator_type:
                if self.python2:
                    method = 'next'
                else:
                    method = '__next__'
                self.add_attribute_dependency(o.inferred_iterator_type, method)
        else:
            self.add_attribute_dependency_for_expr(o.expr, '__aiter__')
            if o.inferred_iterator_type:
                self.add_attribute_dependency(o.inferred_iterator_type, '__anext__')

        self.process_lvalue(o.index)
        if isinstance(o.index, TupleExpr):
            # Process multiple assignment to index variables.
            item_type = o.inferred_item_type
            if item_type:
                # This is similar to above.
                self.add_attribute_dependency(item_type, '__iter__')
                self.add_attribute_dependency(item_type, '__getitem__')
        if o.index_type:
            self.add_type_dependencies(o.index_type)

    def visit_with_stmt(self, o: WithStmt) -> None:
        super().visit_with_stmt(o)
        for e in o.expr:
            if not o.is_async:
                self.add_attribute_dependency_for_expr(e, '__enter__')
                self.add_attribute_dependency_for_expr(e, '__exit__')
            else:
                self.add_attribute_dependency_for_expr(e, '__aenter__')
                self.add_attribute_dependency_for_expr(e, '__aexit__')
        for typ in o.analyzed_types:
            self.add_type_dependencies(typ)

    def visit_print_stmt(self, o: PrintStmt) -> None:
        super().visit_print_stmt(o)
        if o.target:
            self.add_attribute_dependency_for_expr(o.target, 'write')

    def visit_del_stmt(self, o: DelStmt) -> None:
        super().visit_del_stmt(o)
        if isinstance(o.expr, IndexExpr):
            self.add_attribute_dependency_for_expr(o.expr.base, '__delitem__')

    # Expressions

    def process_global_ref_expr(self, o: RefExpr) -> None:
        if o.fullname is not None:
            self.add_dependency(make_trigger(o.fullname))

        # If this is a reference to a type, generate a dependency to its
        # constructor.
        # IDEA: Avoid generating spurious dependencies for except statements,
        #       class attribute references, etc., if performance is a problem.
        typ = get_proper_type(self.type_map.get(o))
        if isinstance(typ, FunctionLike) and typ.is_type_obj():
            class_name = typ.type_object().fullname
            self.add_dependency(make_trigger(class_name + '.__init__'))
            self.add_dependency(make_trigger(class_name + '.__new__'))

    def visit_name_expr(self, o: NameExpr) -> None:
        if o.kind == LDEF:
            # We don't track dependencies to local variables, since they
            # aren't externally visible.
            return
        if o.kind == MDEF:
            # Direct reference to member is only possible in the scope that
            # defined the name, so no dependency is required.
            return
        self.process_global_ref_expr(o)

    def visit_member_expr(self, e: MemberExpr) -> None:
        if isinstance(e.expr, RefExpr) and isinstance(e.expr.node, TypeInfo):
            # Special case class attribute so that we don't depend on "__init__".
            self.add_dependency(make_trigger(e.expr.node.fullname))
        else:
            super().visit_member_expr(e)
        if e.kind is not None:
            # Reference to a module attribute
            self.process_global_ref_expr(e)
        else:
            # Reference to a non-module (or missing) attribute
            if e.expr not in self.type_map:
                # No type available -- this happens for unreachable code. Since it's unreachable,
                # it wasn't type checked and we don't need to generate dependencies.
                return
            if isinstance(e.expr, RefExpr) and isinstance(e.expr.node, MypyFile):
                # Special case: reference to a missing module attribute.
                self.add_dependency(make_trigger(e.expr.node.fullname + '.' + e.name))
                return
            typ = get_proper_type(self.type_map[e.expr])
            self.add_attribute_dependency(typ, e.name)
            if self.use_logical_deps() and isinstance(typ, AnyType):
                name = self.get_unimported_fullname(e, typ)
                if name is not None:
                    # Generate a logical dependency from an unimported
                    # definition (which comes from a missing module).
                    # Example:
                    #     import missing  # "missing" not in build
                    #
                    #     def g() -> None:
                    #         missing.f()  # Generate dependency from "missing.f"
                    self.add_dependency(make_trigger(name))

    def get_unimported_fullname(self, e: MemberExpr, typ: AnyType) -> Optional[str]:
        """If e refers to an unimported definition, infer the fullname of this.

        Return None if e doesn't refer to an unimported definition or if we can't
        determine the name.
        """
        suffix = ''
        # Unwrap nested member expression to handle cases like "a.b.c.d" where
        # "a.b" is a known reference to an unimported module. Find the base
        # reference to an unimported module (such as "a.b") and the name suffix
        # (such as "c.d") needed to build a full name.
        while typ.type_of_any == TypeOfAny.from_another_any and isinstance(e.expr, MemberExpr):
            suffix = '.' + e.name + suffix
            e = e.expr
            if e.expr not in self.type_map:
                return None
            obj_type = get_proper_type(self.type_map[e.expr])
            if not isinstance(obj_type, AnyType):
                # Can't find the base reference to the unimported module.
                return None
            typ = obj_type
        if typ.type_of_any == TypeOfAny.from_unimported_type and typ.missing_import_name:
            # Infer the full name of the unimported definition.
            return typ.missing_import_name + '.' + e.name + suffix
        return None

    def visit_super_expr(self, e: SuperExpr) -> None:
        # Arguments in "super(C, self)" won't generate useful logical deps.
        if not self.use_logical_deps():
            super().visit_super_expr(e)
        if e.info is not None:
            name = e.name
            for base in non_trivial_bases(e.info):
                self.add_dependency(make_trigger(base.fullname + '.' + name))
                if name in base.names:
                    # No need to depend on further base classes, since we found
                    # the target.  This is safe since if the target gets
                    # deleted or modified, we'll trigger it.
                    break

    def visit_call_expr(self, e: CallExpr) -> None:
        if isinstance(e.callee, RefExpr) and e.callee.fullname == 'builtins.isinstance':
            self.process_isinstance_call(e)
        else:
            super().visit_call_expr(e)
            typ = self.type_map.get(e.callee)
            if typ is not None:
                typ = get_proper_type(typ)
                if not isinstance(typ, FunctionLike):
                    self.add_attribute_dependency(typ, '__call__')

    def process_isinstance_call(self, e: CallExpr) -> None:
        """Process "isinstance(...)" in a way to avoid some extra dependencies."""
        if len(e.args) == 2:
            arg = e.args[1]
            if (isinstance(arg, RefExpr)
                    and arg.kind == GDEF
                    and isinstance(arg.node, TypeInfo)
                    and arg.fullname):
                # Special case to avoid redundant dependencies from "__init__".
                self.add_dependency(make_trigger(arg.fullname))
                return
        # In uncommon cases generate normal dependencies. These will include
        # spurious dependencies, but the performance impact is small.
        super().visit_call_expr(e)

    def visit_cast_expr(self, e: CastExpr) -> None:
        super().visit_cast_expr(e)
        self.add_type_dependencies(e.type)

    def visit_type_application(self, e: TypeApplication) -> None:
        super().visit_type_application(e)
        for typ in e.types:
            self.add_type_dependencies(typ)

    def visit_index_expr(self, e: IndexExpr) -> None:
        super().visit_index_expr(e)
        self.add_operator_method_dependency(e.base, '__getitem__')

    def visit_unary_expr(self, e: UnaryExpr) -> None:
        super().visit_unary_expr(e)
        if e.op not in unary_op_methods:
            return
        method = unary_op_methods[e.op]
        self.add_operator_method_dependency(e.expr, method)

    def visit_op_expr(self, e: OpExpr) -> None:
        super().visit_op_expr(e)
        self.process_binary_op(e.op, e.left, e.right)

    def visit_comparison_expr(self, e: ComparisonExpr) -> None:
        super().visit_comparison_expr(e)
        for i, op in enumerate(e.operators):
            left = e.operands[i]
            right = e.operands[i + 1]
            self.process_binary_op(op, left, right)
            if self.python2 and op in ('==', '!=', '<', '<=', '>', '>='):
                self.add_operator_method_dependency(left, '__cmp__')
                self.add_operator_method_dependency(right, '__cmp__')

    def process_binary_op(self, op: str, left: Expression, right: Expression) -> None:
        method = op_methods.get(op)
        if method:
            if op == 'in':
                self.add_operator_method_dependency(right, method)
            else:
                self.add_operator_method_dependency(left, method)
                rev_method = reverse_op_methods.get(method)
                if rev_method:
                    self.add_operator_method_dependency(right, rev_method)

    def add_operator_method_dependency(self, e: Expression, method: str) -> None:
        typ = get_proper_type(self.type_map.get(e))
        if typ is not None:
            self.add_operator_method_dependency_for_type(typ, method)

    def add_operator_method_dependency_for_type(self, typ: ProperType, method: str) -> None:
        # Note that operator methods can't be (non-metaclass) methods of type objects
        # (that is, TypeType objects or Callables representing a type).
        if isinstance(typ, TypeVarType):
            typ = get_proper_type(typ.upper_bound)
        if isinstance(typ, TupleType):
            typ = typ.partial_fallback
        if isinstance(typ, Instance):
            trigger = make_trigger(typ.type.fullname + '.' + method)
            self.add_dependency(trigger)
        elif isinstance(typ, UnionType):
            for item in typ.items:
                self.add_operator_method_dependency_for_type(get_proper_type(item), method)
        elif isinstance(typ, FunctionLike) and typ.is_type_obj():
            self.add_operator_method_dependency_for_type(typ.fallback, method)
        elif isinstance(typ, TypeType):
            if isinstance(typ.item, Instance) and typ.item.type.metaclass_type is not None:
                self.add_operator_method_dependency_for_type(typ.item.type.metaclass_type, method)

    def visit_generator_expr(self, e: GeneratorExpr) -> None:
        super().visit_generator_expr(e)
        for seq in e.sequences:
            self.add_iter_dependency(seq)

    def visit_dictionary_comprehension(self, e: DictionaryComprehension) -> None:
        super().visit_dictionary_comprehension(e)
        for seq in e.sequences:
            self.add_iter_dependency(seq)

    def visit_star_expr(self, e: StarExpr) -> None:
        super().visit_star_expr(e)
        self.add_iter_dependency(e.expr)

    def visit_yield_from_expr(self, e: YieldFromExpr) -> None:
        super().visit_yield_from_expr(e)
        self.add_iter_dependency(e.expr)

    def visit_await_expr(self, e: AwaitExpr) -> None:
        super().visit_await_expr(e)
        self.add_attribute_dependency_for_expr(e.expr, '__await__')

    # Helpers

    def add_type_alias_deps(self, target: str) -> None:
        # Type aliases are special, because some of the dependencies are calculated
        # in semanal.py, before they are expanded.
        if target in self.alias_deps:
            for alias in self.alias_deps[target]:
                self.add_dependency(make_trigger(alias))

    def add_dependency(self, trigger: str, target: Optional[str] = None) -> None:
        """Add dependency from trigger to a target.

        If the target is not given explicitly, use the current target.
        """
        if trigger.startswith(('<builtins.', '<typing.',
                               '<mypy_extensions.', '<typing_extensions.')):
            # Don't track dependencies to certain library modules to keep the size of
            # the dependencies manageable. These dependencies should only
            # change on mypy version updates, which will require a full rebuild
            # anyway.
            return
        if target is None:
            target = self.scope.current_target()
        self.map.setdefault(trigger, set()).add(target)

    def add_type_dependencies(self, typ: Type, target: Optional[str] = None) -> None:
        """Add dependencies to all components of a type.

        Args:
            target: If not None, override the default (current) target of the
                generated dependency.
        """
        for trigger in self.get_type_triggers(typ):
            self.add_dependency(trigger, target)

    def add_attribute_dependency(self, typ: Type, name: str) -> None:
        """Add dependencies for accessing a named attribute of a type."""
        targets = self.attribute_triggers(typ, name)
        for target in targets:
            self.add_dependency(target)

    def attribute_triggers(self, typ: Type, name: str) -> List[str]:
        """Return all triggers associated with the attribute of a type."""
        typ = get_proper_type(typ)
        if isinstance(typ, TypeVarType):
            typ = get_proper_type(typ.upper_bound)
        if isinstance(typ, TupleType):
            typ = typ.partial_fallback
        if isinstance(typ, Instance):
            member = '%s.%s' % (typ.type.fullname, name)
            return [make_trigger(member)]
        elif isinstance(typ, FunctionLike) and typ.is_type_obj():
            member = '%s.%s' % (typ.type_object().fullname, name)
            triggers = [make_trigger(member)]
            triggers.extend(self.attribute_triggers(typ.fallback, name))
            return triggers
        elif isinstance(typ, UnionType):
            targets = []
            for item in typ.items:
                targets.extend(self.attribute_triggers(item, name))
            return targets
        elif isinstance(typ, TypeType):
            triggers = self.attribute_triggers(typ.item, name)
            if isinstance(typ.item, Instance) and typ.item.type.metaclass_type is not None:
                triggers.append(make_trigger('%s.%s' %
                                             (typ.item.type.metaclass_type.type.fullname,
                                              name)))
            return triggers
        else:
            return []

    def add_attribute_dependency_for_expr(self, e: Expression, name: str) -> None:
        typ = self.type_map.get(e)
        if typ is not None:
            self.add_attribute_dependency(typ, name)

    def add_iter_dependency(self, node: Expression) -> None:
        typ = self.type_map.get(node)
        if typ:
            self.add_attribute_dependency(typ, '__iter__')

    def use_logical_deps(self) -> bool:
        return self.options is not None and self.options.logical_deps

    def get_type_triggers(self, typ: Type) -> List[str]:
        return get_type_triggers(typ, self.use_logical_deps())


def get_type_triggers(typ: Type, use_logical_deps: bool) -> List[str]:
    """Return all triggers that correspond to a type becoming stale."""
    return typ.accept(TypeTriggersVisitor(use_logical_deps))


class TypeTriggersVisitor(TypeVisitor[List[str]]):
    def __init__(self, use_logical_deps: bool) -> None:
        self.deps: List[str] = []
        self.use_logical_deps = use_logical_deps

    def get_type_triggers(self, typ: Type) -> List[str]:
        return get_type_triggers(typ, self.use_logical_deps)

    def visit_instance(self, typ: Instance) -> List[str]:
        trigger = make_trigger(typ.type.fullname)
        triggers = [trigger]
        for arg in typ.args:
            triggers.extend(self.get_type_triggers(arg))
        if typ.last_known_value:
            triggers.extend(self.get_type_triggers(typ.last_known_value))
        return triggers

    def visit_type_alias_type(self, typ: TypeAliasType) -> List[str]:
        assert typ.alias is not None
        trigger = make_trigger(typ.alias.fullname)
        triggers = [trigger]
        for arg in typ.args:
            triggers.extend(self.get_type_triggers(arg))
        # TODO: Add guard for infinite recursion here. Moreover, now that type aliases
        # are its own kind of types we can simplify the logic to rely on intermediate
        # dependencies (like for instance types).
        triggers.extend(self.get_type_triggers(typ.alias.target))
        return triggers

    def visit_any(self, typ: AnyType) -> List[str]:
        if typ.missing_import_name is not None:
            return [make_trigger(typ.missing_import_name)]
        return []

    def visit_none_type(self, typ: NoneType) -> List[str]:
        return []

    def visit_callable_type(self, typ: CallableType) -> List[str]:
        triggers = []
        for arg in typ.arg_types:
            triggers.extend(self.get_type_triggers(arg))
        triggers.extend(self.get_type_triggers(typ.ret_type))
        # fallback is a metaclass type for class objects, and is
        # processed separately.
        return triggers

    def visit_overloaded(self, typ: Overloaded) -> List[str]:
        triggers = []
        for item in typ.items:
            triggers.extend(self.get_type_triggers(item))
        return triggers

    def visit_erased_type(self, t: ErasedType) -> List[str]:
        # This type should exist only temporarily during type inference
        assert False, "Should not see an erased type here"

    def visit_deleted_type(self, typ: DeletedType) -> List[str]:
        return []

    def visit_partial_type(self, typ: PartialType) -> List[str]:
        assert False, "Should not see a partial type here"

    def visit_tuple_type(self, typ: TupleType) -> List[str]:
        triggers = []
        for item in typ.items:
            triggers.extend(self.get_type_triggers(item))
        triggers.extend(self.get_type_triggers(typ.partial_fallback))
        return triggers

    def visit_type_type(self, typ: TypeType) -> List[str]:
        triggers = self.get_type_triggers(typ.item)
        if not self.use_logical_deps:
            old_triggers = triggers[:]
            for trigger in old_triggers:
                triggers.append(trigger.rstrip('>') + '.__init__>')
                triggers.append(trigger.rstrip('>') + '.__new__>')
        return triggers

    def visit_type_var(self, typ: TypeVarType) -> List[str]:
        triggers = []
        if typ.fullname:
            triggers.append(make_trigger(typ.fullname))
        if typ.upper_bound:
            triggers.extend(self.get_type_triggers(typ.upper_bound))
        for val in typ.values:
            triggers.extend(self.get_type_triggers(val))
        return triggers

    def visit_param_spec(self, typ: ParamSpecType) -> List[str]:
        triggers = []
        if typ.fullname:
            triggers.append(make_trigger(typ.fullname))
        triggers.extend(self.get_type_triggers(typ.upper_bound))
        return triggers

    def visit_unpack_type(self, typ: UnpackType) -> List[str]:
        return typ.type.accept(self)

    def visit_typeddict_type(self, typ: TypedDictType) -> List[str]:
        triggers = []
        for item in typ.items.values():
            triggers.extend(self.get_type_triggers(item))
        triggers.extend(self.get_type_triggers(typ.fallback))
        return triggers

    def visit_literal_type(self, typ: LiteralType) -> List[str]:
        return self.get_type_triggers(typ.fallback)

    def visit_unbound_type(self, typ: UnboundType) -> List[str]:
        return []

    def visit_uninhabited_type(self, typ: UninhabitedType) -> List[str]:
        return []

    def visit_union_type(self, typ: UnionType) -> List[str]:
        triggers = []
        for item in typ.items:
            triggers.extend(self.get_type_triggers(item))
        return triggers


def merge_dependencies(new_deps: Dict[str, Set[str]],
                       deps: Dict[str, Set[str]]) -> None:
    for trigger, targets in new_deps.items():
        deps.setdefault(trigger, set()).update(targets)


def non_trivial_bases(info: TypeInfo) -> List[TypeInfo]:
    return [base for base in info.mro[1:]
            if base.fullname != 'builtins.object']


def has_user_bases(info: TypeInfo) -> bool:
    return any(base.module_name not in ('builtins', 'typing', 'enum') for base in info.mro[1:])


def dump_all_dependencies(modules: Dict[str, MypyFile],
                          type_map: Dict[Expression, Type],
                          python_version: Tuple[int, int],
                          options: Options) -> None:
    """Generate dependencies for all interesting modules and print them to stdout."""
    all_deps: Dict[str, Set[str]] = {}
    for id, node in modules.items():
        # Uncomment for debugging:
        # print('processing', id)
        if id in ('builtins', 'typing') or '/typeshed/' in node.path:
            continue
        assert id == node.fullname
        deps = get_dependencies(node, type_map, python_version, options)
        for trigger, targets in deps.items():
            all_deps.setdefault(trigger, set()).update(targets)
    TypeState.add_all_protocol_deps(all_deps)

    for trigger, targets in sorted(all_deps.items(), key=lambda x: x[0]):
        print(trigger)
        for target in sorted(targets):
            print('    %s' % target)