refactor: migrate checks.ts utility to core and deduplicate (#18139)

packages/cli/src/utils/checks.test.ts

@@ -1,32 +0,0 @@
-/**
- * @license
- * Copyright 2025 Google LLC
- * SPDX-License-Identifier: Apache-2.0
- */
-
-import { describe, it, expect } from 'vitest';
-import { checkExhaustive, assumeExhaustive } from './checks.js';
-
-describe('checks', () => {
-  describe('checkExhaustive', () => {
-    it('should throw an error with default message', () => {
-      expect(() => {
-        checkExhaustive('unexpected' as never);
-      }).toThrow('unexpected value unexpected!');
-    });
-
-    it('should throw an error with custom message', () => {
-      expect(() => {
-        checkExhaustive('unexpected' as never, 'custom message');
-      }).toThrow('custom message');
-    });
-  });
-
-  describe('assumeExhaustive', () => {
-    it('should do nothing', () => {
-      expect(() => {
-        assumeExhaustive('unexpected' as never);
-      }).not.toThrow();
-    });
-  });
-});

packages/cli/src/utils/checks.ts

@@ -1,28 +0,0 @@
-/**
- * @license
- * Copyright 2025 Google LLC
- * SPDX-License-Identifier: Apache-2.0
- */
-
-/* Fail to compile on unexpected values. */
-export function assumeExhaustive(_value: never): void {}
-
-/**
- * Throws an exception on unexpected values.
- *
- * A common use case is switch statements:
- * switch(enumValue) {
- *   case Enum.A:
- *   case Enum.B:
- *     break;
- *   default:
- *     checkExhaustive(enumValue);
- * }
- */
-export function checkExhaustive(
-  value: never,
-  msg = `unexpected value ${value}!`,
-): never {
-  assumeExhaustive(value);
-  throw new Error(msg);
-}

packages/cli/src/utils/sessionUtils.ts

@@ -4,20 +4,18 @@
  * SPDX-License-Identifier: Apache-2.0
  */
 
-import type {
-  Config,
-  ConversationRecord,
-  MessageRecord,
-} from '@google/gemini-cli-core';
 import {
+  checkExhaustive,
   partListUnionToString,
   SESSION_FILE_PREFIX,
+  type Config,
+  type ConversationRecord,
+  type MessageRecord,
 } from '@google/gemini-cli-core';
 import * as fs from 'node:fs/promises';
 import path from 'node:path';
 import { stripUnsafeCharacters } from '../ui/utils/textUtils.js';
 import type { Part } from '@google/genai';
-import { checkExhaustive } from './checks.js';
 import {
   MessageType,
   ToolCallStatus,