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195 lines
6.2 KiB
195 lines
6.2 KiB
4 months ago
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import type { ASTNode } from './ast';
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import { Kind } from './kinds';
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/**
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* A visitor is provided to visit, it contains the collection of
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* relevant functions to be called during the visitor's traversal.
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*/
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export declare type ASTVisitor = EnterLeaveVisitor<ASTNode> | KindVisitor;
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declare type KindVisitor = {
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readonly [NodeT in ASTNode as NodeT['kind']]?:
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| ASTVisitFn<NodeT>
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| EnterLeaveVisitor<NodeT>;
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};
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interface EnterLeaveVisitor<TVisitedNode extends ASTNode> {
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readonly enter?: ASTVisitFn<TVisitedNode>;
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readonly leave?: ASTVisitFn<TVisitedNode>;
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}
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/**
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* A visitor is comprised of visit functions, which are called on each node
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* during the visitor's traversal.
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*/
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export declare type ASTVisitFn<TVisitedNode extends ASTNode> = (
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/** The current node being visiting. */
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node: TVisitedNode,
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/** The index or key to this node from the parent node or Array. */
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key: string | number | undefined,
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/** The parent immediately above this node, which may be an Array. */
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parent: ASTNode | ReadonlyArray<ASTNode> | undefined,
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/** The key path to get to this node from the root node. */
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path: ReadonlyArray<string | number>,
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/**
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* All nodes and Arrays visited before reaching parent of this node.
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* These correspond to array indices in `path`.
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* Note: ancestors includes arrays which contain the parent of visited node.
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*/
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ancestors: ReadonlyArray<ASTNode | ReadonlyArray<ASTNode>>,
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) => any;
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/**
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* A reducer is comprised of reducer functions which convert AST nodes into
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* another form.
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*/
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export declare type ASTReducer<R> = {
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readonly [NodeT in ASTNode as NodeT['kind']]?: {
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readonly enter?: ASTVisitFn<NodeT>;
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readonly leave: ASTReducerFn<NodeT, R>;
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};
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};
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declare type ASTReducerFn<TReducedNode extends ASTNode, R> = (
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/** The current node being visiting. */
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node: {
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[K in keyof TReducedNode]: ReducedField<TReducedNode[K], R>;
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},
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/** The index or key to this node from the parent node or Array. */
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key: string | number | undefined,
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/** The parent immediately above this node, which may be an Array. */
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parent: ASTNode | ReadonlyArray<ASTNode> | undefined,
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/** The key path to get to this node from the root node. */
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path: ReadonlyArray<string | number>,
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/**
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* All nodes and Arrays visited before reaching parent of this node.
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* These correspond to array indices in `path`.
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* Note: ancestors includes arrays which contain the parent of visited node.
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*/
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ancestors: ReadonlyArray<ASTNode | ReadonlyArray<ASTNode>>,
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) => R;
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declare type ReducedField<T, R> = T extends null | undefined
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? T
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: T extends ReadonlyArray<any>
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? ReadonlyArray<R>
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: R;
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/**
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* A KeyMap describes each the traversable properties of each kind of node.
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*
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* @deprecated Please inline it. Will be removed in v17
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*/
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export declare type ASTVisitorKeyMap = {
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[NodeT in ASTNode as NodeT['kind']]?: ReadonlyArray<keyof NodeT>;
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};
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export declare const BREAK: unknown;
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/**
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* visit() will walk through an AST using a depth-first traversal, calling
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* the visitor's enter function at each node in the traversal, and calling the
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* leave function after visiting that node and all of its child nodes.
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*
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* By returning different values from the enter and leave functions, the
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* behavior of the visitor can be altered, including skipping over a sub-tree of
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* the AST (by returning false), editing the AST by returning a value or null
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* to remove the value, or to stop the whole traversal by returning BREAK.
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*
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* When using visit() to edit an AST, the original AST will not be modified, and
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* a new version of the AST with the changes applied will be returned from the
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* visit function.
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*
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* ```ts
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* const editedAST = visit(ast, {
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* enter(node, key, parent, path, ancestors) {
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* // @return
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* // undefined: no action
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* // false: skip visiting this node
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* // visitor.BREAK: stop visiting altogether
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* // null: delete this node
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* // any value: replace this node with the returned value
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* },
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* leave(node, key, parent, path, ancestors) {
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* // @return
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* // undefined: no action
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* // false: no action
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* // visitor.BREAK: stop visiting altogether
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* // null: delete this node
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* // any value: replace this node with the returned value
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* }
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* });
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* ```
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*
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* Alternatively to providing enter() and leave() functions, a visitor can
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* instead provide functions named the same as the kinds of AST nodes, or
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* enter/leave visitors at a named key, leading to three permutations of the
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* visitor API:
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*
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* 1) Named visitors triggered when entering a node of a specific kind.
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*
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* ```ts
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* visit(ast, {
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* Kind(node) {
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* // enter the "Kind" node
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* }
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* })
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* ```
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*
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* 2) Named visitors that trigger upon entering and leaving a node of a specific kind.
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*
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* ```ts
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* visit(ast, {
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* Kind: {
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* enter(node) {
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* // enter the "Kind" node
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* }
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* leave(node) {
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* // leave the "Kind" node
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* }
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* }
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* })
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* ```
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*
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* 3) Generic visitors that trigger upon entering and leaving any node.
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*
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* ```ts
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* visit(ast, {
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* enter(node) {
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* // enter any node
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* },
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* leave(node) {
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* // leave any node
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* }
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* })
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* ```
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*/
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export declare function visit<N extends ASTNode>(
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root: N,
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visitor: ASTVisitor,
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visitorKeys?: ASTVisitorKeyMap,
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): N;
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export declare function visit<R>(
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root: ASTNode,
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visitor: ASTReducer<R>,
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visitorKeys?: ASTVisitorKeyMap,
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): R;
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/**
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* Creates a new visitor instance which delegates to many visitors to run in
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* parallel. Each visitor will be visited for each node before moving on.
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*
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* If a prior visitor edits a node, no following visitors will see that node.
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*/
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export declare function visitInParallel(
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visitors: ReadonlyArray<ASTVisitor>,
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): ASTVisitor;
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/**
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* Given a visitor instance and a node kind, return EnterLeaveVisitor for that kind.
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*/
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export declare function getEnterLeaveForKind(
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visitor: ASTVisitor,
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kind: Kind,
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): EnterLeaveVisitor<ASTNode>;
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/**
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* Given a visitor instance, if it is leaving or not, and a node kind, return
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* the function the visitor runtime should call.
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*
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* @deprecated Please use `getEnterLeaveForKind` instead. Will be removed in v17
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*/
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export declare function getVisitFn(
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visitor: ASTVisitor,
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kind: Kind,
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isLeaving: boolean,
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): ASTVisitFn<ASTNode> | undefined;
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export {};
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