iterating an enum is now an error

[gpra]

Iterating a string enum in strict mode is not allowed since 3.6.2. Is this a breaking change or a bug?

Sample code:

// sample.ts
// compile with: `tsc --strict sample.ts`
enum DAYS { Monday = 'monday', Tuesday = 'tuesday' }

for (const a in DAYS) {
  const x = DAYS[a];  // <- This is now an error
  console.log(x);
}

tsc --strict sample.ts

TSC 3.5.2: Compiles OK

TSC 3.6.2: reports an error:
error TS7053: Element implicitly has an 'any' type because expression of type 'string' can't be used to index type 'typeof DAYS'.

[chermme]

I confirm, it happens to me as well, I couldn't find any way to overcome this problem.

[jochenonline]

A workaround until the problem is solved is to use an interim object:

let _DAYS: {[propName: string]: string} = <any> DAYS;

[bytenik]

Still having this issue.

[bdunks]

As another alternative that feels a bit less like a work-around (at least to me) is to use type assertions after creating a new type based on the enum keys.

enum DAYS {
  Monday = 'monday',
  Tuesday = 'tuesday',
}

type DaysKeys = keyof typeof DAYS; //<- Equivalent to type DaysKeys = 'Monday' | 'Tuesday'; 
  
for (const a in DAYS) {
  const x = DAYS[a as DaysKeys]; //<- assert type
  console.log(x);
}