typescriptenumsvisual-studio-2017typescript2.4

TypeScript's string enums - "Type ... is not assignable to type ..."

I have recently upgraded the version of TypeScript from 2.3.4 to 2.4.0 hoping to use the string enums. To my dismay, however, I have been greeted with the error messages:

Severity  Code    Description Project File    Line    Suppression State
Error TS2322  Type '"E"' is not assignable to type
'StepType'.   ClientApp (tsconfig
project)  Z:\SMART\Smart\Smart\ClientApp\app\models\process.model.ts  17  Active
Error TS2322  Type '"S"' is not assignable to type
'StepType'.   ClientApp (tsconfig
project)  Z:\SMART\Smart\Smart\ClientApp\app\models\process.model.ts  14  Active
Error TS2322  Type '"A"' is not assignable to type
'StepType'.   ClientApp (tsconfig
project)  Z:\SMART\Smart\Smart\ClientApp\app\models\process.model.ts  15  Active
Error TS2322  Type '"D"' is not assignable to type
'StepType'.   ClientApp (tsconfig
project)  Z:\SMART\Smart\Smart\ClientApp\app\models\process.model.ts  16  Active

The error messages apply to the following code snippet (with the line numbers):

13. export enum StepType {
14.    Start = 'S',
15.    Activity = 'A',
16.    Decision = 'D',
17.    End = 'E'
18. }

I am using Visual Studio 2017 which claims TypeScript 2.4.0 is installed:

enter image description here

I searched through TypeScript's issues, but without luck. Does anybody know how to fix it?

Solution

  • Inspired by Duncan's answer, I found the root cause. Although the application was using TypeScript 2.4, VS's IntelliSense was still stuck in 2.3. VS IntelliSense was not updated

    The way to resolve the issue was to download and install TypeScript 2.4 SDK and then select from the options the newer version:

    enter image description here