Imported const enum is not inlined in generated code

TypeScript Version: 2.4.0

Code

// a.ts
export const enum Foo {
  Bar = 'bar'
}

// b.ts
import { Foo } from './a'

Foo.Bar // TypeError or ReferenceError, depending on how it's compiled

Expected behavior: Foo.Bar to be replaced with 'bar'

Actual behavior: The import is deleted and Foo.Bar is left as is

[mhegazy]

I’ve also encountered this problem when transpileOnly: true. Without transpileOnly, I can’t use multi-threading to speed up my webpack build (ts-loader, happypack, fork-ts-checker-webpack-plugin). Unfortunately, I’m dealing with +100,000 lines of legacy code, so removing all const enums is not feasible.

transpileOnly means transpile every file one at a time… when the compiler is looking at one file, it has no way to know if the reference it is looking at is a const enum or not, since the declaration is in another file that it does not have access to…

so I do not think you can mix these two concepts, const enums (require whole program information), and transpileOnly (one file at a time).

[elijah-schow]

I’ve also encountered this problem when transpileOnly: true. Without transpileOnly, I can’t use multi-threading to speed up my webpack build (ts-loader, happypack, fork-ts-checker-webpack-plugin). Unfortunately, I’m dealing with +100,000 lines of legacy code, so removing all const enums is not feasible.

Typescript version: 2.6.1