293eba6203
Fixes #20703 with solution suggested in https://github.com/Microsoft/TypeScript/issues/20703#issuecomment-361434795 Previously, `--isolatedModules` gave an error for any ambient const enum, which meant that some third-party libraries would always give errors even if the ambient const enums they declare were never used. Now, we only give an error when an ambient const enum is referenced, which allows such libraries to still be used as long as the const enums are never accessed. Some nuances: * As before, the error is only surfaced for *ambient* const enums. With non-ambient const enums, we know that an `isolatedModules` build will emit the enum and produce a plain reference rather than inlining the constant, so everything will still work. * I originally planned to do this check in the code path that inlines the constant, but that code is only exercised at emit time, so, for example, the TS language service wasn't giving an error in my editor. Instead, I do the check at typecheck time next to another const-enum-related check. * This can be a breaking change when using `skipLibCheck` because the error is typically moved from a .d.ts file to a .ts file. Testing done: I ran this TS build on a large project of mine that previously had disabled `isolatedModules` so I could use the `chalk` library. With `isolatedModules` enabled, there was no longer an error in the chalk typedefs, and a reference to the `Level` const enum produced an error in my editor.
8 lines
124 B
TypeScript
8 lines
124 B
TypeScript
// @isolatedModules: true
|
|
// @target: es6
|
|
|
|
// @filename: file1.ts
|
|
|
|
declare const enum E { X = 1}
|
|
export var y = E.X;
|