Bug Report

🔎 Search Terms

function incompatible overload implementation signature assignability TS2394

🕗 Version & Regression Information

• This is the behavior in every version I tried, and I reviewed the FAQ for entries about function overloads

⏯ Playground Link

Playground link with relevant code

💻 Code

function example(overloaded: string): string;
function example(actual: number, option?: boolean): string {
  return `${actual}${option}`;
}

🙁 Actual behavior

A single line of error message that doesn't indicate which parameter or return type is the issue.

function example(overloaded: string): string;
//       ~~~~~~~
// Error: This overload signature is not compatible with its implementation signature.

🙂 Expected behavior

Can we elaborate on that error message with the first assignability issue?

Bikeshedding on the error message specifics welcome...

function example(overloaded: string): string;
//       ~~~~~~~
// Error: This overload signature is not compatible with its implementation signature.
//   Overload parameter 'overload: string' is not assignable to implementation parameter 'actual: number'.