Throw compile error when using an enum imported from a declaration file

[MatthiasKunnen]

Search Terms

Declaration files Definition files .d.ts enums

Suggestion

Currently exporting an enum from a .d.ts file and importing/using this enum in a common TS file is allowed. Compilation succeeds but the compiled code will not run since the .d.ts file is not compiled thus the enum values are lost. I would like this to error on compilation.

Use Cases

I just ran into this problem and unfortunately the cause was masked by some other tools resulting in a lot of wasted time.

Examples

// bar.d.ts
export enum Status {
   Open = 'Open',
}

// server.ts
import {Status} from './bar';
const open = Status.Open;

I would like to get something along these lines:

server.ts:3:13 - error TS????: Values from enum 'Status' imported from declaration file cannot be used.

3       const open = Status.Open;
                     ~~~~~~

Checklist

My suggestion meets these guidelines:

• This wouldn't be a breaking change in existing TypeScript/JavaScript code
• This wouldn't change the runtime behavior of existing JavaScript code
• This could be implemented without emitting different JS based on the types of the expressions it would not break working code
• This isn't a runtime feature (e.g. library functionality, non-ECMAScript syntax with JavaScript output, etc.)
• This feature would agree with the rest of TypeScript's Design Goals.

[RyanCavanaugh]

This falls squarely under the "We believe what you told us" rule. If there isn't a module named ./bar at runtime present with a Status value export, then it is incorrect to write a .d.ts file claiming there is.

[MatthiasKunnen]

Gotcha