Inconsistent Behavior with `readonly` in Template Literal Indexed Access Types about typescript HOT 3 CLOSED

This is working as intended. We consider an element access to be read-only when all applicable index signatures have a readonly modifier. In the example, the string "head-haha-tail" matches three index signatures, two of which are not read-only. Therefore, the assignment is permitted. A similar thing happens when resolving the properties of the Pick<Example, keyof Example> mapped type. For each generated index signature we query the combined read-only-ness of applicable index signatures in the source type, and `head-${string}-tail` matches three, two of which aren't read-only.

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@ahejlsberg I appreciate your response.

Sorry I didn't make it clear before, I understand that the behavior is working as expected, but my confusion is:

The string index head-${string}-tail matches three index signatures, two of which are not read-only. So, when we try to add readonly to head-${string}-tail only, there should be an error prompt, but the actual situation seems to be correct.

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This issue has been marked as "Working as Intended" and has seen no recent activity. It has been automatically closed for house-keeping purposes.

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