Major fixes and new features

venv/lib/python3.12/site-packages/mypy/treetransform.py

@@ -0,0 +1,800 @@
+"""Base visitor that implements an identity AST transform.
+
+Subclass TransformVisitor to perform non-trivial transformations.
+"""
+
+from __future__ import annotations
+
+from typing import Iterable, Optional, cast
+
+from mypy.nodes import (
+    GDEF,
+    REVEAL_TYPE,
+    Argument,
+    AssertStmt,
+    AssertTypeExpr,
+    AssignmentExpr,
+    AssignmentStmt,
+    AwaitExpr,
+    Block,
+    BreakStmt,
+    BytesExpr,
+    CallExpr,
+    CastExpr,
+    ClassDef,
+    ComparisonExpr,
+    ComplexExpr,
+    ConditionalExpr,
+    ContinueStmt,
+    Decorator,
+    DelStmt,
+    DictExpr,
+    DictionaryComprehension,
+    EllipsisExpr,
+    EnumCallExpr,
+    Expression,
+    ExpressionStmt,
+    FloatExpr,
+    ForStmt,
+    FuncDef,
+    FuncItem,
+    GeneratorExpr,
+    GlobalDecl,
+    IfStmt,
+    Import,
+    ImportAll,
+    ImportFrom,
+    IndexExpr,
+    IntExpr,
+    LambdaExpr,
+    ListComprehension,
+    ListExpr,
+    MatchStmt,
+    MemberExpr,
+    MypyFile,
+    NamedTupleExpr,
+    NameExpr,
+    NewTypeExpr,
+    Node,
+    NonlocalDecl,
+    OperatorAssignmentStmt,
+    OpExpr,
+    OverloadedFuncDef,
+    OverloadPart,
+    ParamSpecExpr,
+    PassStmt,
+    PromoteExpr,
+    RaiseStmt,
+    RefExpr,
+    ReturnStmt,
+    RevealExpr,
+    SetComprehension,
+    SetExpr,
+    SliceExpr,
+    StarExpr,
+    Statement,
+    StrExpr,
+    SuperExpr,
+    SymbolTable,
+    TempNode,
+    TryStmt,
+    TupleExpr,
+    TypeAliasExpr,
+    TypeApplication,
+    TypedDictExpr,
+    TypeVarExpr,
+    TypeVarTupleExpr,
+    UnaryExpr,
+    Var,
+    WhileStmt,
+    WithStmt,
+    YieldExpr,
+    YieldFromExpr,
+)
+from mypy.patterns import (
+    AsPattern,
+    ClassPattern,
+    MappingPattern,
+    OrPattern,
+    Pattern,
+    SequencePattern,
+    SingletonPattern,
+    StarredPattern,
+    ValuePattern,
+)
+from mypy.traverser import TraverserVisitor
+from mypy.types import FunctionLike, ProperType, Type
+from mypy.util import replace_object_state
+from mypy.visitor import NodeVisitor
+
+
+class TransformVisitor(NodeVisitor[Node]):
+    """Transform a semantically analyzed AST (or subtree) to an identical copy.
+
+    Use the node() method to transform an AST node.
+
+    Subclass to perform a non-identity transform.
+
+    Notes:
+
+     * This can only be used to transform functions or classes, not top-level
+       statements, and/or modules as a whole.
+     * Do not duplicate TypeInfo nodes. This would generally not be desirable.
+     * Only update some name binding cross-references, but only those that
+       refer to Var, Decorator or FuncDef nodes, not those targeting ClassDef or
+       TypeInfo nodes.
+     * Types are not transformed, but you can override type() to also perform
+       type transformation.
+
+    TODO nested classes and functions have not been tested well enough
+    """
+
+    def __init__(self) -> None:
+        # To simplify testing, set this flag to True if you want to transform
+        # all statements in a file (this is prohibited in normal mode).
+        self.test_only = False
+        # There may be multiple references to a Var node. Keep track of
+        # Var translations using a dictionary.
+        self.var_map: dict[Var, Var] = {}
+        # These are uninitialized placeholder nodes used temporarily for nested
+        # functions while we are transforming a top-level function. This maps an
+        # untransformed node to a placeholder (which will later become the
+        # transformed node).
+        self.func_placeholder_map: dict[FuncDef, FuncDef] = {}
+
+    def visit_mypy_file(self, node: MypyFile) -> MypyFile:
+        assert self.test_only, "This visitor should not be used for whole files."
+        # NOTE: The 'names' and 'imports' instance variables will be empty!
+        ignored_lines = {line: codes.copy() for line, codes in node.ignored_lines.items()}
+        new = MypyFile(self.statements(node.defs), [], node.is_bom, ignored_lines=ignored_lines)
+        new._fullname = node._fullname
+        new.path = node.path
+        new.names = SymbolTable()
+        return new
+
+    def visit_import(self, node: Import) -> Import:
+        return Import(node.ids.copy())
+
+    def visit_import_from(self, node: ImportFrom) -> ImportFrom:
+        return ImportFrom(node.id, node.relative, node.names.copy())
+
+    def visit_import_all(self, node: ImportAll) -> ImportAll:
+        return ImportAll(node.id, node.relative)
+
+    def copy_argument(self, argument: Argument) -> Argument:
+        arg = Argument(
+            self.visit_var(argument.variable),
+            argument.type_annotation,
+            argument.initializer,
+            argument.kind,
+        )
+
+        # Refresh lines of the inner things
+        arg.set_line(argument)
+
+        return arg
+
+    def visit_func_def(self, node: FuncDef) -> FuncDef:
+        # Note that a FuncDef must be transformed to a FuncDef.
+
+        # These contortions are needed to handle the case of recursive
+        # references inside the function being transformed.
+        # Set up placeholder nodes for references within this function
+        # to other functions defined inside it.
+        # Don't create an entry for this function itself though,
+        # since we want self-references to point to the original
+        # function if this is the top-level node we are transforming.
+        init = FuncMapInitializer(self)
+        for stmt in node.body.body:
+            stmt.accept(init)
+
+        new = FuncDef(
+            node.name,
+            [self.copy_argument(arg) for arg in node.arguments],
+            self.block(node.body),
+            cast(Optional[FunctionLike], self.optional_type(node.type)),
+        )
+
+        self.copy_function_attributes(new, node)
+
+        new._fullname = node._fullname
+        new.is_decorated = node.is_decorated
+        new.is_conditional = node.is_conditional
+        new.abstract_status = node.abstract_status
+        new.is_static = node.is_static
+        new.is_class = node.is_class
+        new.is_property = node.is_property
+        new.is_final = node.is_final
+        new.original_def = node.original_def
+
+        if node in self.func_placeholder_map:
+            # There is a placeholder definition for this function. Replace
+            # the attributes of the placeholder with those form the transformed
+            # function. We know that the classes will be identical (otherwise
+            # this wouldn't work).
+            result = self.func_placeholder_map[node]
+            replace_object_state(result, new)
+            return result
+        else:
+            return new
+
+    def visit_lambda_expr(self, node: LambdaExpr) -> LambdaExpr:
+        new = LambdaExpr(
+            [self.copy_argument(arg) for arg in node.arguments],
+            self.block(node.body),
+            cast(Optional[FunctionLike], self.optional_type(node.type)),
+        )
+        self.copy_function_attributes(new, node)
+        return new
+
+    def copy_function_attributes(self, new: FuncItem, original: FuncItem) -> None:
+        new.info = original.info
+        new.min_args = original.min_args
+        new.max_pos = original.max_pos
+        new.is_overload = original.is_overload
+        new.is_generator = original.is_generator
+        new.is_coroutine = original.is_coroutine
+        new.is_async_generator = original.is_async_generator
+        new.is_awaitable_coroutine = original.is_awaitable_coroutine
+        new.line = original.line
+
+    def visit_overloaded_func_def(self, node: OverloadedFuncDef) -> OverloadedFuncDef:
+        items = [cast(OverloadPart, item.accept(self)) for item in node.items]
+        for newitem, olditem in zip(items, node.items):
+            newitem.line = olditem.line
+        new = OverloadedFuncDef(items)
+        new._fullname = node._fullname
+        new_type = self.optional_type(node.type)
+        assert isinstance(new_type, ProperType)
+        new.type = new_type
+        new.info = node.info
+        new.is_static = node.is_static
+        new.is_class = node.is_class
+        new.is_property = node.is_property
+        new.is_final = node.is_final
+        if node.impl:
+            new.impl = cast(OverloadPart, node.impl.accept(self))
+        return new
+
+    def visit_class_def(self, node: ClassDef) -> ClassDef:
+        new = ClassDef(
+            node.name,
+            self.block(node.defs),
+            node.type_vars,
+            self.expressions(node.base_type_exprs),
+            self.optional_expr(node.metaclass),
+        )
+        new.fullname = node.fullname
+        new.info = node.info
+        new.decorators = [self.expr(decorator) for decorator in node.decorators]
+        return new
+
+    def visit_global_decl(self, node: GlobalDecl) -> GlobalDecl:
+        return GlobalDecl(node.names.copy())
+
+    def visit_nonlocal_decl(self, node: NonlocalDecl) -> NonlocalDecl:
+        return NonlocalDecl(node.names.copy())
+
+    def visit_block(self, node: Block) -> Block:
+        return Block(self.statements(node.body))
+
+    def visit_decorator(self, node: Decorator) -> Decorator:
+        # Note that a Decorator must be transformed to a Decorator.
+        func = self.visit_func_def(node.func)
+        func.line = node.func.line
+        new = Decorator(func, self.expressions(node.decorators), self.visit_var(node.var))
+        new.is_overload = node.is_overload
+        return new
+
+    def visit_var(self, node: Var) -> Var:
+        # Note that a Var must be transformed to a Var.
+        if node in self.var_map:
+            return self.var_map[node]
+        new = Var(node.name, self.optional_type(node.type))
+        new.line = node.line
+        new._fullname = node._fullname
+        new.info = node.info
+        new.is_self = node.is_self
+        new.is_ready = node.is_ready
+        new.is_initialized_in_class = node.is_initialized_in_class
+        new.is_staticmethod = node.is_staticmethod
+        new.is_classmethod = node.is_classmethod
+        new.is_property = node.is_property
+        new.is_final = node.is_final
+        new.final_value = node.final_value
+        new.final_unset_in_class = node.final_unset_in_class
+        new.final_set_in_init = node.final_set_in_init
+        new.set_line(node)
+        self.var_map[node] = new
+        return new
+
+    def visit_expression_stmt(self, node: ExpressionStmt) -> ExpressionStmt:
+        return ExpressionStmt(self.expr(node.expr))
+
+    def visit_assignment_stmt(self, node: AssignmentStmt) -> AssignmentStmt:
+        return self.duplicate_assignment(node)
+
+    def duplicate_assignment(self, node: AssignmentStmt) -> AssignmentStmt:
+        new = AssignmentStmt(
+            self.expressions(node.lvalues),
+            self.expr(node.rvalue),
+            self.optional_type(node.unanalyzed_type),
+        )
+        new.line = node.line
+        new.is_final_def = node.is_final_def
+        new.type = self.optional_type(node.type)
+        return new
+
+    def visit_operator_assignment_stmt(
+        self, node: OperatorAssignmentStmt
+    ) -> OperatorAssignmentStmt:
+        return OperatorAssignmentStmt(node.op, self.expr(node.lvalue), self.expr(node.rvalue))
+
+    def visit_while_stmt(self, node: WhileStmt) -> WhileStmt:
+        return WhileStmt(
+            self.expr(node.expr), self.block(node.body), self.optional_block(node.else_body)
+        )
+
+    def visit_for_stmt(self, node: ForStmt) -> ForStmt:
+        new = ForStmt(
+            self.expr(node.index),
+            self.expr(node.expr),
+            self.block(node.body),
+            self.optional_block(node.else_body),
+            self.optional_type(node.unanalyzed_index_type),
+        )
+        new.is_async = node.is_async
+        new.index_type = self.optional_type(node.index_type)
+        return new
+
+    def visit_return_stmt(self, node: ReturnStmt) -> ReturnStmt:
+        return ReturnStmt(self.optional_expr(node.expr))
+
+    def visit_assert_stmt(self, node: AssertStmt) -> AssertStmt:
+        return AssertStmt(self.expr(node.expr), self.optional_expr(node.msg))
+
+    def visit_del_stmt(self, node: DelStmt) -> DelStmt:
+        return DelStmt(self.expr(node.expr))
+
+    def visit_if_stmt(self, node: IfStmt) -> IfStmt:
+        return IfStmt(
+            self.expressions(node.expr),
+            self.blocks(node.body),
+            self.optional_block(node.else_body),
+        )
+
+    def visit_break_stmt(self, node: BreakStmt) -> BreakStmt:
+        return BreakStmt()
+
+    def visit_continue_stmt(self, node: ContinueStmt) -> ContinueStmt:
+        return ContinueStmt()
+
+    def visit_pass_stmt(self, node: PassStmt) -> PassStmt:
+        return PassStmt()
+
+    def visit_raise_stmt(self, node: RaiseStmt) -> RaiseStmt:
+        return RaiseStmt(self.optional_expr(node.expr), self.optional_expr(node.from_expr))
+
+    def visit_try_stmt(self, node: TryStmt) -> TryStmt:
+        new = TryStmt(
+            self.block(node.body),
+            self.optional_names(node.vars),
+            self.optional_expressions(node.types),
+            self.blocks(node.handlers),
+            self.optional_block(node.else_body),
+            self.optional_block(node.finally_body),
+        )
+        new.is_star = node.is_star
+        return new
+
+    def visit_with_stmt(self, node: WithStmt) -> WithStmt:
+        new = WithStmt(
+            self.expressions(node.expr),
+            self.optional_expressions(node.target),
+            self.block(node.body),
+            self.optional_type(node.unanalyzed_type),
+        )
+        new.is_async = node.is_async
+        new.analyzed_types = [self.type(typ) for typ in node.analyzed_types]
+        return new
+
+    def visit_as_pattern(self, p: AsPattern) -> AsPattern:
+        return AsPattern(
+            pattern=self.pattern(p.pattern) if p.pattern is not None else None,
+            name=self.duplicate_name(p.name) if p.name is not None else None,
+        )
+
+    def visit_or_pattern(self, p: OrPattern) -> OrPattern:
+        return OrPattern([self.pattern(pat) for pat in p.patterns])
+
+    def visit_value_pattern(self, p: ValuePattern) -> ValuePattern:
+        return ValuePattern(self.expr(p.expr))
+
+    def visit_singleton_pattern(self, p: SingletonPattern) -> SingletonPattern:
+        return SingletonPattern(p.value)
+
+    def visit_sequence_pattern(self, p: SequencePattern) -> SequencePattern:
+        return SequencePattern([self.pattern(pat) for pat in p.patterns])
+
+    def visit_starred_pattern(self, p: StarredPattern) -> StarredPattern:
+        return StarredPattern(self.duplicate_name(p.capture) if p.capture is not None else None)
+
+    def visit_mapping_pattern(self, p: MappingPattern) -> MappingPattern:
+        return MappingPattern(
+            keys=[self.expr(expr) for expr in p.keys],
+            values=[self.pattern(pat) for pat in p.values],
+            rest=self.duplicate_name(p.rest) if p.rest is not None else None,
+        )
+
+    def visit_class_pattern(self, p: ClassPattern) -> ClassPattern:
+        class_ref = p.class_ref.accept(self)
+        assert isinstance(class_ref, RefExpr)
+        return ClassPattern(
+            class_ref=class_ref,
+            positionals=[self.pattern(pat) for pat in p.positionals],
+            keyword_keys=list(p.keyword_keys),
+            keyword_values=[self.pattern(pat) for pat in p.keyword_values],
+        )
+
+    def visit_match_stmt(self, o: MatchStmt) -> MatchStmt:
+        return MatchStmt(
+            subject=self.expr(o.subject),
+            patterns=[self.pattern(p) for p in o.patterns],
+            guards=self.optional_expressions(o.guards),
+            bodies=self.blocks(o.bodies),
+        )
+
+    def visit_star_expr(self, node: StarExpr) -> StarExpr:
+        return StarExpr(node.expr)
+
+    def visit_int_expr(self, node: IntExpr) -> IntExpr:
+        return IntExpr(node.value)
+
+    def visit_str_expr(self, node: StrExpr) -> StrExpr:
+        return StrExpr(node.value)
+
+    def visit_bytes_expr(self, node: BytesExpr) -> BytesExpr:
+        return BytesExpr(node.value)
+
+    def visit_float_expr(self, node: FloatExpr) -> FloatExpr:
+        return FloatExpr(node.value)
+
+    def visit_complex_expr(self, node: ComplexExpr) -> ComplexExpr:
+        return ComplexExpr(node.value)
+
+    def visit_ellipsis(self, node: EllipsisExpr) -> EllipsisExpr:
+        return EllipsisExpr()
+
+    def visit_name_expr(self, node: NameExpr) -> NameExpr:
+        return self.duplicate_name(node)
+
+    def duplicate_name(self, node: NameExpr) -> NameExpr:
+        # This method is used when the transform result must be a NameExpr.
+        # visit_name_expr() is used when there is no such restriction.
+        new = NameExpr(node.name)
+        self.copy_ref(new, node)
+        new.is_special_form = node.is_special_form
+        return new
+
+    def visit_member_expr(self, node: MemberExpr) -> MemberExpr:
+        member = MemberExpr(self.expr(node.expr), node.name)
+        if node.def_var:
+            # This refers to an attribute and we don't transform attributes by default,
+            # just normal variables.
+            member.def_var = node.def_var
+        self.copy_ref(member, node)
+        return member
+
+    def copy_ref(self, new: RefExpr, original: RefExpr) -> None:
+        new.kind = original.kind
+        new.fullname = original.fullname
+        target = original.node
+        if isinstance(target, Var):
+            # Do not transform references to global variables. See
+            # testGenericFunctionAliasExpand for an example where this is important.
+            if original.kind != GDEF:
+                target = self.visit_var(target)
+        elif isinstance(target, Decorator):
+            target = self.visit_var(target.var)
+        elif isinstance(target, FuncDef):
+            # Use a placeholder node for the function if it exists.
+            target = self.func_placeholder_map.get(target, target)
+        new.node = target
+        new.is_new_def = original.is_new_def
+        new.is_inferred_def = original.is_inferred_def
+
+    def visit_yield_from_expr(self, node: YieldFromExpr) -> YieldFromExpr:
+        return YieldFromExpr(self.expr(node.expr))
+
+    def visit_yield_expr(self, node: YieldExpr) -> YieldExpr:
+        return YieldExpr(self.optional_expr(node.expr))
+
+    def visit_await_expr(self, node: AwaitExpr) -> AwaitExpr:
+        return AwaitExpr(self.expr(node.expr))
+
+    def visit_call_expr(self, node: CallExpr) -> CallExpr:
+        return CallExpr(
+            self.expr(node.callee),
+            self.expressions(node.args),
+            node.arg_kinds.copy(),
+            node.arg_names.copy(),
+            self.optional_expr(node.analyzed),
+        )
+
+    def visit_op_expr(self, node: OpExpr) -> OpExpr:
+        new = OpExpr(
+            node.op,
+            self.expr(node.left),
+            self.expr(node.right),
+            cast(Optional[TypeAliasExpr], self.optional_expr(node.analyzed)),
+        )
+        new.method_type = self.optional_type(node.method_type)
+        return new
+
+    def visit_comparison_expr(self, node: ComparisonExpr) -> ComparisonExpr:
+        new = ComparisonExpr(node.operators, self.expressions(node.operands))
+        new.method_types = [self.optional_type(t) for t in node.method_types]
+        return new
+
+    def visit_cast_expr(self, node: CastExpr) -> CastExpr:
+        return CastExpr(self.expr(node.expr), self.type(node.type))
+
+    def visit_assert_type_expr(self, node: AssertTypeExpr) -> AssertTypeExpr:
+        return AssertTypeExpr(self.expr(node.expr), self.type(node.type))
+
+    def visit_reveal_expr(self, node: RevealExpr) -> RevealExpr:
+        if node.kind == REVEAL_TYPE:
+            assert node.expr is not None
+            return RevealExpr(kind=REVEAL_TYPE, expr=self.expr(node.expr))
+        else:
+            # Reveal locals expressions don't have any sub expressions
+            return node
+
+    def visit_super_expr(self, node: SuperExpr) -> SuperExpr:
+        call = self.expr(node.call)
+        assert isinstance(call, CallExpr)
+        new = SuperExpr(node.name, call)
+        new.info = node.info
+        return new
+
+    def visit_assignment_expr(self, node: AssignmentExpr) -> AssignmentExpr:
+        return AssignmentExpr(self.expr(node.target), self.expr(node.value))
+
+    def visit_unary_expr(self, node: UnaryExpr) -> UnaryExpr:
+        new = UnaryExpr(node.op, self.expr(node.expr))
+        new.method_type = self.optional_type(node.method_type)
+        return new
+
+    def visit_list_expr(self, node: ListExpr) -> ListExpr:
+        return ListExpr(self.expressions(node.items))
+
+    def visit_dict_expr(self, node: DictExpr) -> DictExpr:
+        return DictExpr(
+            [(self.expr(key) if key else None, self.expr(value)) for key, value in node.items]
+        )
+
+    def visit_tuple_expr(self, node: TupleExpr) -> TupleExpr:
+        return TupleExpr(self.expressions(node.items))
+
+    def visit_set_expr(self, node: SetExpr) -> SetExpr:
+        return SetExpr(self.expressions(node.items))
+
+    def visit_index_expr(self, node: IndexExpr) -> IndexExpr:
+        new = IndexExpr(self.expr(node.base), self.expr(node.index))
+        if node.method_type:
+            new.method_type = self.type(node.method_type)
+        if node.analyzed:
+            if isinstance(node.analyzed, TypeApplication):
+                new.analyzed = self.visit_type_application(node.analyzed)
+            else:
+                new.analyzed = self.visit_type_alias_expr(node.analyzed)
+            new.analyzed.set_line(node.analyzed)
+        return new
+
+    def visit_type_application(self, node: TypeApplication) -> TypeApplication:
+        return TypeApplication(self.expr(node.expr), self.types(node.types))
+
+    def visit_list_comprehension(self, node: ListComprehension) -> ListComprehension:
+        generator = self.duplicate_generator(node.generator)
+        generator.set_line(node.generator)
+        return ListComprehension(generator)
+
+    def visit_set_comprehension(self, node: SetComprehension) -> SetComprehension:
+        generator = self.duplicate_generator(node.generator)
+        generator.set_line(node.generator)
+        return SetComprehension(generator)
+
+    def visit_dictionary_comprehension(
+        self, node: DictionaryComprehension
+    ) -> DictionaryComprehension:
+        return DictionaryComprehension(
+            self.expr(node.key),
+            self.expr(node.value),
+            [self.expr(index) for index in node.indices],
+            [self.expr(s) for s in node.sequences],
+            [[self.expr(cond) for cond in conditions] for conditions in node.condlists],
+            node.is_async,
+        )
+
+    def visit_generator_expr(self, node: GeneratorExpr) -> GeneratorExpr:
+        return self.duplicate_generator(node)
+
+    def duplicate_generator(self, node: GeneratorExpr) -> GeneratorExpr:
+        return GeneratorExpr(
+            self.expr(node.left_expr),
+            [self.expr(index) for index in node.indices],
+            [self.expr(s) for s in node.sequences],
+            [[self.expr(cond) for cond in conditions] for conditions in node.condlists],
+            node.is_async,
+        )
+
+    def visit_slice_expr(self, node: SliceExpr) -> SliceExpr:
+        return SliceExpr(
+            self.optional_expr(node.begin_index),
+            self.optional_expr(node.end_index),
+            self.optional_expr(node.stride),
+        )
+
+    def visit_conditional_expr(self, node: ConditionalExpr) -> ConditionalExpr:
+        return ConditionalExpr(
+            self.expr(node.cond), self.expr(node.if_expr), self.expr(node.else_expr)
+        )
+
+    def visit_type_var_expr(self, node: TypeVarExpr) -> TypeVarExpr:
+        return TypeVarExpr(
+            node.name,
+            node.fullname,
+            self.types(node.values),
+            self.type(node.upper_bound),
+            self.type(node.default),
+            variance=node.variance,
+        )
+
+    def visit_paramspec_expr(self, node: ParamSpecExpr) -> ParamSpecExpr:
+        return ParamSpecExpr(
+            node.name,
+            node.fullname,
+            self.type(node.upper_bound),
+            self.type(node.default),
+            variance=node.variance,
+        )
+
+    def visit_type_var_tuple_expr(self, node: TypeVarTupleExpr) -> TypeVarTupleExpr:
+        return TypeVarTupleExpr(
+            node.name,
+            node.fullname,
+            self.type(node.upper_bound),
+            node.tuple_fallback,
+            self.type(node.default),
+            variance=node.variance,
+        )
+
+    def visit_type_alias_expr(self, node: TypeAliasExpr) -> TypeAliasExpr:
+        return TypeAliasExpr(node.node)
+
+    def visit_newtype_expr(self, node: NewTypeExpr) -> NewTypeExpr:
+        res = NewTypeExpr(node.name, node.old_type, line=node.line, column=node.column)
+        res.info = node.info
+        return res
+
+    def visit_namedtuple_expr(self, node: NamedTupleExpr) -> NamedTupleExpr:
+        return NamedTupleExpr(node.info)
+
+    def visit_enum_call_expr(self, node: EnumCallExpr) -> EnumCallExpr:
+        return EnumCallExpr(node.info, node.items, node.values)
+
+    def visit_typeddict_expr(self, node: TypedDictExpr) -> Node:
+        return TypedDictExpr(node.info)
+
+    def visit__promote_expr(self, node: PromoteExpr) -> PromoteExpr:
+        return PromoteExpr(node.type)
+
+    def visit_temp_node(self, node: TempNode) -> TempNode:
+        return TempNode(self.type(node.type))
+
+    def node(self, node: Node) -> Node:
+        new = node.accept(self)
+        new.set_line(node)
+        return new
+
+    def mypyfile(self, node: MypyFile) -> MypyFile:
+        new = node.accept(self)
+        assert isinstance(new, MypyFile)
+        new.set_line(node)
+        return new
+
+    def expr(self, expr: Expression) -> Expression:
+        new = expr.accept(self)
+        assert isinstance(new, Expression)
+        new.set_line(expr)
+        return new
+
+    def stmt(self, stmt: Statement) -> Statement:
+        new = stmt.accept(self)
+        assert isinstance(new, Statement)
+        new.set_line(stmt)
+        return new
+
+    def pattern(self, pattern: Pattern) -> Pattern:
+        new = pattern.accept(self)
+        assert isinstance(new, Pattern)
+        new.set_line(pattern)
+        return new
+
+    # Helpers
+    #
+    # All the node helpers also propagate line numbers.
+
+    def optional_expr(self, expr: Expression | None) -> Expression | None:
+        if expr:
+            return self.expr(expr)
+        else:
+            return None
+
+    def block(self, block: Block) -> Block:
+        new = self.visit_block(block)
+        new.line = block.line
+        return new
+
+    def optional_block(self, block: Block | None) -> Block | None:
+        if block:
+            return self.block(block)
+        else:
+            return None
+
+    def statements(self, statements: list[Statement]) -> list[Statement]:
+        return [self.stmt(stmt) for stmt in statements]
+
+    def expressions(self, expressions: list[Expression]) -> list[Expression]:
+        return [self.expr(expr) for expr in expressions]
+
+    def optional_expressions(
+        self, expressions: Iterable[Expression | None]
+    ) -> list[Expression | None]:
+        return [self.optional_expr(expr) for expr in expressions]
+
+    def blocks(self, blocks: list[Block]) -> list[Block]:
+        return [self.block(block) for block in blocks]
+
+    def names(self, names: list[NameExpr]) -> list[NameExpr]:
+        return [self.duplicate_name(name) for name in names]
+
+    def optional_names(self, names: Iterable[NameExpr | None]) -> list[NameExpr | None]:
+        result: list[NameExpr | None] = []
+        for name in names:
+            if name:
+                result.append(self.duplicate_name(name))
+            else:
+                result.append(None)
+        return result
+
+    def type(self, type: Type) -> Type:
+        # Override this method to transform types.
+        return type
+
+    def optional_type(self, type: Type | None) -> Type | None:
+        if type:
+            return self.type(type)
+        else:
+            return None
+
+    def types(self, types: list[Type]) -> list[Type]:
+        return [self.type(type) for type in types]
+
+
+class FuncMapInitializer(TraverserVisitor):
+    """This traverser creates mappings from nested FuncDefs to placeholder FuncDefs.
+
+    The placeholders will later be replaced with transformed nodes.
+    """
+
+    def __init__(self, transformer: TransformVisitor) -> None:
+        self.transformer = transformer
+
+    def visit_func_def(self, node: FuncDef) -> None:
+        if node not in self.transformer.func_placeholder_map:
+            # Haven't seen this FuncDef before, so create a placeholder node.
+            self.transformer.func_placeholder_map[node] = FuncDef(
+                node.name, node.arguments, node.body, None
+            )
+        super().visit_func_def(node)