E0260: TypeScript non-null assertion is not allowed on parameters

In TypeScript, ! after an expression is a non-null assertion. It is a syntax error to write a non-null assertion after a function parameter:

// color cannot be null.
function colorToHexCode(color!: string): string {
  switch (color) {
    // ...
  }
}

To fix this error, remove the ! and ensure the parameter's type does not include null:

// color cannot be null.
function colorToHexCode(color: string): string {
  switch (color) {
    // ...
  }
}

Introduced in quick-lint-js version 2.7.0.

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