Callback function needs name gotcha

[lcoenen]

Hi!

Thanks for your work, guys! I like playing with Assemblyscript and they're using it in fluence, which is a great project.

Just a little gotcha I noticed - I tried to use a callback function like that:

/*
 *
 * This will call the translate function until it gets
 * an answer or an error
 *
 */
export function engine(input: string, query: (string) => string): string {
  return 'to be implemented';
}

but had the following error:

ERROR AS200: Conversion from type '(theQuery: ~lib/string/String) => ~lib/string/String' to '() => ~lib/string/String' requires an explicit cast.

     let answer: string = engine('incoming message', query);
                                                   ~~~~~
 in assembly/__tests__/main.spec.ts(91,50)

albeit it is valid Typescript.

I had to explicitly indicate an arg name for it to work:

export function engine(input: string, query: (queryStr: string) => string): string {
  return 'to be implemented';
}

[MaxGraey]

function engine(input: string, query: (string) => string): string {

This restricted in TypeScript with turned on "noImplicitAny" and IDE / TS diagnostics should inform about it. See typescriptlang playground

But thanks. We will improve error messages with such of case

[dcodeIO]

Should actually be valid TypeScript, but for a different reason. What TS infers there is a (string: any) => string, with string being the name of the variable, not the type. What happens there is that upon (string) the parser still isn't sure whether it is dealing with a parenthesized type or a function type, hence not emitting any diagnostics. That diagnostic needs a fix, but omitting the type won't work still.