"declare function"'s need to converted to single function.

[AaronNGray]

AFAICT "declare function"'s need to converted to single function.

For example :-

declare function didYouMean(suggestions: $ReadOnlyArray<string>): string;
declare function didYouMean(
  subMessage: string,
  suggestions: $ReadOnlyArray<string>,
): string;
    
// eslint-disable-next-line no-redeclare
export default function didYouMean(firstArg, secondArg?) { ... }

needs converting to :-

export default function didYouMean(firstArg: string | ReadonlyArray<string>, secondArg?:ReadonlyArray<string>): string { ... }

otherwise I am getting the error :-

 error TS2384: Overload signatures must all be ambient or non-ambient.

[AaronNGray]

I am trying to work out how to go about this given the current structure of babel-plugin-flow-to-typescript.
There appears to be no context object passed through the visitors.
The other way would to do this as a separate "pass" at the Program level.

[zxbodya]

ideally this should be converted to:

function didYouMean(suggestions: ReadonlyArray<string>): string;
function didYouMean(
  subMessage: string,
  suggestions: ReadonlyArray<string>,
): string;
    
// eslint-disable-next-line no-redeclare
function didYouMean(firstArg, secondArg?):string { }

export default didYouMean;

there are are two issues to be fixed:

1. remove declare - typescript supports function overrides without it(however, declare should be removed only if the actual implementation is present)
2. separating export from function declaration - in typescript, it should be either on all declarations or separate from them.

I think the best place to do it would be exit() in Program visitor, implemented it here: zxbodya/flowts@a3032f2