Don't cache child lists for tokens

src/compiler/factory/nodeChildren.ts

@@ -1,14 +1,20 @@
-import { Node } from "../_namespaces/ts";
+import {
+    isToken,
+    Node,
+} from "../_namespaces/ts";
 
-const nodeChildren = new WeakMap<Node, Node[] | undefined>();
+const nodeChildren = new WeakMap<Node, readonly Node[] | undefined>();
+
+const emptyChildren: readonly Node[] = Object.freeze([]);
 
 /** @internal */
-export function getNodeChildren(node: Node): Node[] | undefined {
+export function getNodeChildren(node: Node): readonly Node[] | undefined {
+    if (isToken(node)) return emptyChildren;
     return nodeChildren.get(node);
 }
 
 /** @internal */
-export function setNodeChildren(node: Node, children: Node[]): Node[] {
+export function setNodeChildren(node: Node, children: readonly Node[]): readonly Node[] {
     nodeChildren.set(node, children);
     return children;
 }

src/compiler/factory/nodeFactory.ts

@@ -6209,7 +6209,7 @@ export function createNodeFactory(flags: NodeFactoryFlags, baseFactory: BaseNode
     }
 
     // @api
-    function createSyntaxList(children: Node[]) {
+    function createSyntaxList(children: readonly Node[]) {
         const node = createBaseNode<SyntaxList>(SyntaxKind.SyntaxList);
         setNodeChildren(node, children);
         return node;

src/compiler/types.ts

@@ -9006,7 +9006,7 @@ export interface NodeFactory {
     // Synthetic Nodes
     //
     /** @internal */ createSyntheticExpression(type: Type, isSpread?: boolean, tupleNameSource?: ParameterDeclaration | NamedTupleMember): SyntheticExpression;
-    /** @internal */ createSyntaxList(children: Node[]): SyntaxList;
+    /** @internal */ createSyntaxList(children: readonly Node[]): SyntaxList;
 
     //
     // Transformation nodes

src/services/services.ts

@@ -438,7 +438,7 @@ class NodeObject<TKind extends SyntaxKind> implements Node {
         return this.getChildren(sourceFile)[index];
     }
 
-    public getChildren(sourceFile?: SourceFileLike): Node[] {
+    public getChildren(sourceFile?: SourceFileLike): readonly Node[] {
         this.assertHasRealPosition("Node without a real position cannot be scanned and thus has no token nodes - use forEachChild and collect the result if that's fine");
         return getNodeChildren(this) ?? setNodeChildren(this, createChildren(this, sourceFile));
     }
@@ -473,7 +473,7 @@ class NodeObject<TKind extends SyntaxKind> implements Node {
     }
 }
 
-function createChildren(node: Node, sourceFile: SourceFileLike | undefined): Node[] {
+function createChildren(node: Node, sourceFile: SourceFileLike | undefined): readonly Node[] {
     if (!isNodeKind(node.kind)) {
         return emptyArray;
     }

src/services/smartSelection.ts

@@ -279,7 +279,7 @@ function getSelectionChildren(node: Node): readonly Node[] {
  * Groups sibling nodes together into their own SyntaxList if they
  * a) are adjacent, AND b) match a predicate function.
  */
-function groupChildren(children: Node[], groupOn: (child: Node) => boolean): Node[] {
+function groupChildren(children: readonly Node[], groupOn: (child: Node) => boolean): Node[] {
     const result: Node[] = [];
     let group: Node[] | undefined;
     for (const child of children) {
@@ -315,7 +315,7 @@ function groupChildren(children: Node[], groupOn: (child: Node) => boolean): Nod
  * @param separateTrailingSemicolon If the last token is a semicolon, it will be returned as a separate
  * child rather than be included in the right-hand group.
  */
-function splitChildren(children: Node[], pivotOn: (child: Node) => boolean, separateTrailingSemicolon = true): Node[] {
+function splitChildren(children: readonly Node[], pivotOn: (child: Node) => boolean, separateTrailingSemicolon = true): readonly Node[] {
     if (children.length < 2) {
         return children;
     }
@@ -336,7 +336,7 @@ function splitChildren(children: Node[], pivotOn: (child: Node) => boolean, sepa
     return separateLastToken ? result.concat(lastToken) : result;
 }
 
-function createSyntaxList(children: Node[]): SyntaxList {
+function createSyntaxList(children: readonly Node[]): SyntaxList {
     Debug.assertGreaterThanOrEqual(children.length, 1);
     return setTextRangePosEnd(parseNodeFactory.createSyntaxList(children), children[0].pos, last(children).end);
 }

src/services/types.ts

@@ -49,9 +49,9 @@ declare module "../compiler/types" {
         getSourceFile(): SourceFile;
         getChildCount(sourceFile?: SourceFile): number;
         getChildAt(index: number, sourceFile?: SourceFile): Node;
-        getChildren(sourceFile?: SourceFile): Node[];
+        getChildren(sourceFile?: SourceFile): readonly Node[];
         /** @internal */
-        getChildren(sourceFile?: SourceFileLike): Node[]; // eslint-disable-line @typescript-eslint/unified-signatures
+        getChildren(sourceFile?: SourceFileLike): readonly Node[]; // eslint-disable-line @typescript-eslint/unified-signatures
         getStart(sourceFile?: SourceFile, includeJsDocComment?: boolean): number;
         /** @internal */
         getStart(sourceFile?: SourceFileLike, includeJsDocComment?: boolean): number; // eslint-disable-line @typescript-eslint/unified-signatures

src/services/utilities.ts

@@ -1830,7 +1830,7 @@ function findRightmostToken(n: Node, sourceFile: SourceFileLike): Node | undefin
 /**
  * Finds the rightmost child to the left of `children[exclusiveStartPosition]` which is a non-all-whitespace token or has constituent tokens.
  */
-function findRightmostChildNodeWithTokens(children: Node[], exclusiveStartPosition: number, sourceFile: SourceFileLike, parentKind: SyntaxKind): Node | undefined {
+function findRightmostChildNodeWithTokens(children: readonly Node[], exclusiveStartPosition: number, sourceFile: SourceFileLike, parentKind: SyntaxKind): Node | undefined {
     for (let i = exclusiveStartPosition - 1; i >= 0; i--) {
         const child = children[i];
 

tests/baselines/reference/api/typescript.d.ts

@@ -4215,7 +4215,7 @@ declare namespace ts {
         getSourceFile(): SourceFile;
         getChildCount(sourceFile?: SourceFile): number;
         getChildAt(index: number, sourceFile?: SourceFile): Node;
-        getChildren(sourceFile?: SourceFile): Node[];
+        getChildren(sourceFile?: SourceFile): readonly Node[];
         getStart(sourceFile?: SourceFile, includeJsDocComment?: boolean): number;
         getFullStart(): number;
         getEnd(): number;