chore: using type narrowing instead of using 'as'

tests/client/handlers/vaults.test.ts

@@ -3,7 +3,6 @@ import type { FileSystem } from '@/types';
 import type { VaultId } from '@/ids';
 import type NodeManager from '@/nodes/NodeManager';
 import type {
-  ErrorMessage,
   LogEntryMessage,
   SecretContentMessage,
   VaultListMessage,
@@ -65,6 +64,7 @@ import {
   vaultsSecretsStat,
   vaultsVersion,
 } from '@/client/callers';
+import * as utils from '@/utils';
 import * as keysUtils from '@/keys/utils';
 import * as nodesUtils from '@/nodes/utils';
 import * as vaultsUtils from '@/vaults/utils';
@@ -1371,9 +1371,9 @@ describe('vaultsSecretsMkdir', () => {
     await writer.close();
     for await (const data of response.readable) {
       expect(data.type).toEqual('error');
-      const error = data as ErrorMessage;
-      expect(error.code).toEqual('ENOENT');
-      expect(error.reason).toEqual(dirPath);
+      if (data.type !== 'error') utils.never();
+      expect(data.code).toEqual('ENOENT');
+      expect(data.reason).toEqual(dirPath);
     }
     await vaultManager.withVaults([vaultId], async (vault) => {
       await vault.readF(async (efs) => {
@@ -1439,9 +1439,8 @@ describe('vaultsSecretsMkdir', () => {
     // Check if the operation concluded as expected
     for await (const data of response.readable) {
       if (data.type !== 'success') {
-        const error = data as ErrorMessage;
-        expect(error.code).toEqual('ENOENT');
-        expect(error.reason).toEqual(dirPath3);
+        expect(data.code).toEqual('ENOENT');
+        expect(data.reason).toEqual(dirPath3);
       }
     }
     await vaultManager.withVaults(
@@ -1475,9 +1474,9 @@ describe('vaultsSecretsMkdir', () => {
     // Check if the operation concluded as expected
     for await (const data of response.readable) {
       expect(data.type).toEqual('error');
-      const error = data as ErrorMessage;
-      expect(error.code).toEqual('EEXIST');
-      expect(error.reason).toEqual(dirPath);
+      if (data.type !== 'error') utils.never();
+      expect(data.code).toEqual('EEXIST');
+      expect(data.reason).toEqual(dirPath);
     }
     await vaultManager.withVaults([vaultId], async (vault) => {
       await vault.readF(async (efs) => {