Bug Report

🔎 Search Terms

key remapping, error message, 2345

🕗 Version & Regression Information

• This is the behavior in every version I tried since key remapping was introduced in TS4.1; I don't see relevant FAQ entries

⏯ Playground Link

Playground link with relevant code

💻 Code

function foo<T extends { [K in keyof T as `${Extract<K, string>}Oops`]: T[K] }>(x: T) { }
const x = { prop: 123 };
foo(x); // error!
//  ~ <-- Argument of type '{ prop: number; }' is not assignable to parameter of type '{ propOops: number; }'.
// Property 'prop' is missing in type '{ prop: number; }' but required in type '{ propOops: number; }'. (2345) 

🙁 Actual behavior

The last line of the error message says that the property prop is missing in the type { prop: number }, but it's not.

🙂 Expected behavior

The error should probably say

Property 'propOops' is missing in type '{ prop: number; }' but required in type '{ propOops: number; }'.

I guess the error message is using the original key when it should be using the remapped key? 🤷‍♂️