Flow: Return type annotations not supported on arrow functions

[clark-pan]

As an aside, sorry for the issue spam over the last few days. I'm really liking this package so far.

[Thom1729]

As an aside, sorry for the issue spam over the last few days.

The more the better! The bugs are out there, and I can't fix them if I don't know about them.

Unfortunately, this is another case where perfect parsing is impossible. The current syntax uses an imperfect lookahead to detect arrow functions. We can (and should) modify that lookahead to account for type annotations. However, since type annotations can involve arbitrarily complex expressions, it won't be perfect.

I might not get to this for a few days, as I'll be travelling.

[Thom1729]

I've just released version 1.0.18, which handles simple return type declarations.

[neutraali]

I've just released version 1.0.18, which handles simple return type declarations.

Is this in effect (1.0.19)? I'm assuming "simple return types" refer to, for example, primitives.

// Syntax highlighting OK
value = () => {
	// Do stuff
	return this._input.value;
}
// Syntax highlighting not OK
value = (): string => {
	// Do stuff
	return this._input.value;
}

[Thom1729]

It works for me. Try rebuilding your syntaxes.

I'm assuming "simple return types" refer to, for example, primitives.

Yes, single identifiers in general.

[neutraali]

Might be a bit of an edge-case, but the return type declarations seem to break string templates with substitutions for some reason (class context):

export default class Foo {
	// Highlighting OK
	bar = (you: string = 'World') => {
		return `Hello ${you}! ${'Welcome!'}`;
	}
	// Highlighting broken beyond this
	baz = (you: string = 'World'): string => {
		return `Hello ${you}! ${'Welcome!'}`;
	}
}

[Thom1729]

It's misparsing string => ... as a function type, and everything after that is breaking. I'll have to figure out what the right algorithm is for that. (Unfortunately, the Flow docs are very vague on syntax issues.)

[Thom1729]

Should be fully working by now.