Custom string based type is not allowed to index record

[wclr]

TypeScript Version: 3.7.x-dev.201xxxxx

Thre is a MyKeyType to make strings type more distinctive just for typing purposes.

Code

type MyKeyType = string & { __myKey?: true }

// works ok
const indexed: Record<MyKeyType, string> = {} 

const key: MyKeyType = 'myKey'

// Error: Element implicitly has an 'any' type because
// expression of type 'MyKeyType' can't be used to index type 'Record<MyKeyType, string>'
const x = indexed[key]

Expected behavior:

Allow to use the same type for indexing as was used in Record declaration.

Actual behavior:

Error: Element implicitly has an 'any' type because
expression of type 'MyKeyType' can't be used to index type 'Record<MyKeyType, string>'

Also now indexed can not be indexed by "pure" string type.

[MartinJohns]

Duplicate of #37448.

[typescript-bot]

This issue has been marked as a 'Duplicate' and has seen no recent activity. It has been automatically closed for house-keeping purposes.