Fix LanguageModelToolResultPart2 inheritance for instanceof checks (microsoft#264362)

* Initial plan

* Fix LanguageModelToolResultPart2 inheritance for instanceof checks

Co-authored-by: connor4312 <2230985+connor4312@users.noreply.github.com>

---------

Co-authored-by: copilot-swe-agent[bot] <198982749+Copilot@users.noreply.github.com>
Co-authored-by: connor4312 <2230985+connor4312@users.noreply.github.com>

Author: Copilot

src/vs/workbench/api/common/extHostTypes.ts

@@ -3468,16 +3468,13 @@ export class LanguageModelToolResultPart implements vscode.LanguageModelToolResu
 	}
 }
 
-export class LanguageModelToolResultPart2 implements vscode.LanguageModelToolResultPart2 {
+export class LanguageModelToolResultPart2 extends LanguageModelToolResultPart implements vscode.LanguageModelToolResultPart2 {
 
-	callId: string;
-	content: (LanguageModelTextPart | LanguageModelPromptTsxPart | LanguageModelDataPart | unknown)[];
-	isError: boolean;
+	declare content: (LanguageModelTextPart | LanguageModelPromptTsxPart | LanguageModelDataPart | unknown)[];
 
 	constructor(callId: string, content: (LanguageModelTextPart | LanguageModelPromptTsxPart | LanguageModelDataPart | unknown)[], isError?: boolean) {
-		this.callId = callId;
+		super(callId, content, isError);
 		this.content = content;
-		this.isError = isError ?? false;
 	}
 }
 

src/vs/workbench/api/test/browser/extHostTypes.test.ts

@@ -783,4 +783,21 @@ suite('ExtHostTypes', function () {
 		m.content = 'Hello';
 		assert.deepStrictEqual(m.content, [new types.LanguageModelTextPart('Hello')]);
 	});
+
+	test('LanguageModelToolResultPart2 instanceof LanguageModelToolResultPart', function () {
+		// Test that LanguageModelToolResultPart2 extends LanguageModelToolResultPart for instanceof checks
+		const part1 = new types.LanguageModelToolResultPart('call1', [new types.LanguageModelTextPart('text')]);
+		const part2 = new types.LanguageModelToolResultPart2('call2', [new types.LanguageModelTextPart('text')]);
+
+		// Basic instanceof checks
+		assert.ok(part1 instanceof types.LanguageModelToolResultPart);
+		assert.ok(part2 instanceof types.LanguageModelToolResultPart, 'LanguageModelToolResultPart2 should be instanceof LanguageModelToolResultPart');
+		assert.ok(part2 instanceof types.LanguageModelToolResultPart2);
+
+		// Verify properties are accessible
+		assert.strictEqual(part1.callId, 'call1');
+		assert.strictEqual(part2.callId, 'call2');
+		assert.strictEqual(part1.isError, false);
+		assert.strictEqual(part2.isError, false);
+	});
 });