Ensure that we copy empty NodeArrays during transform (#48490)

Author: jakebailey

src/compiler/checker.ts

@@ -5262,7 +5262,18 @@ namespace ts {
                         if (!nodeIsSynthesized(node) && getParseTreeNode(node) === node) {
                             return node;
                         }
-                        return setTextRange(factory.cloneNode(visitEachChild(node, deepCloneOrReuseNode, nullTransformationContext)), node);
+                        return setTextRange(factory.cloneNode(visitEachChild(node, deepCloneOrReuseNode, nullTransformationContext, deepCloneOrReuseNodes)), node);
+                    }
+
+                    function deepCloneOrReuseNodes<T extends Node>(nodes: NodeArray<T>, visitor: Visitor | undefined, test?: (node: Node) => boolean, start?: number, count?: number): NodeArray<T>;
+                    function deepCloneOrReuseNodes<T extends Node>(nodes: NodeArray<T> | undefined, visitor: Visitor | undefined, test?: (node: Node) => boolean, start?: number, count?: number): NodeArray<T> | undefined;
+                    function deepCloneOrReuseNodes<T extends Node>(nodes: NodeArray<T> | undefined, visitor: Visitor | undefined, test?: (node: Node) => boolean, start?: number, count?: number): NodeArray<T> | undefined {
+                        if (nodes && nodes.length === 0) {
+                            // Ensure we explicitly make a copy of an empty array; visitNodes will not do this unless the array has elements,
+                            // which can lead to us reusing the same empty NodeArray more than once within the same AST during type noding.
+                            return setTextRange(factory.createNodeArray<T>(/*nodes*/ undefined, nodes.hasTrailingComma), nodes);
+                        }
+                        return visitNodes(nodes, visitor, test, start, count);
                     }
                 }
 

tests/cases/fourslash/completionsOverridingMethodCrash1.ts

@@ -0,0 +1,28 @@
+/// <reference path="fourslash.ts" />
+
+// @newline: LF
+// @Filename: a.ts
+////declare class Component<T> {
+////    setState(stateHandler: ((oldState: T, newState: T) => void)): void;
+////}
+////
+////class SubComponent extends Component<{}> {
+////    /*$*/
+////}
+
+verify.completions({
+    marker: "$",
+    isNewIdentifierLocation: true,
+    preferences: {
+        includeCompletionsWithInsertText: true,
+        includeCompletionsWithSnippetText: false,
+        includeCompletionsWithClassMemberSnippets: true,
+    },
+    includes: [
+        {
+            name: "setState",
+            sortText: completion.SortText.ClassMemberSnippets,
+            insertText: "setState(stateHandler: (oldState: {}, newState: {}) => void): void {\n}",
+        }
+    ]
+});