Add support for enums as parameters or return types

[nickyr]

You always have to fake enums in PHP since they're not supported. Psalm could help this!

One option would be to do a syntax like this:

/**
 * @return 'A'|'B'|'C'
 */

The quotes would differentiate the strings from classes, and this would fit pretty naturally with the way Psalm currently allows notation with false like

/**
 * @return string|false
 */

Or, you could do something like

/**
 * @return enum{'A', 'B', 'C'}
 */

which would kind of match the current fancy array syntax.

[nickyr]

#17 could make this even awesomer

[muglug]

What do you think of https://flowtype.org/docs/builtins.html#literal-types? Pretty much identical to your first proposition. And it could be used together with #18 to avoid repetition

[erunion]

Seems like this might break from the standard PHPDoc @return annotation.

[nickyr]

Looks good!

@erunion there's a @psalm-return annotation for things that don't match PHPDoc

[muglug]

How about

/*
 * @psalm-param enum-string('some-option'|Class::CONSTANT) $foo
 */
function takesConstant(string $foo) {}

[erunion]

Oh I like that.

[nickyr]

that looks good! but it should support ints as well as strings

[muglug]

@JanTvrdik did you have any plan to support a particular format in PHPStan, given you already have value types?

[muglug]

@psalm-param enum-string("hello"|"goodbye")|enum-int(1 |2 | C::A)

and also

@psalm-param keys-of(C::A)|keys-of(C::B)|values-of(C::D)

[weirdan]

enum-string("hello"|"goodbye") should probably use comma as a separator, to match that of enum-int.

I reckon it's just a syntax proposal at this stage, and it's not implemented yet, right?

[muglug]

Yeah, have updated - was unintentional

[muglug]

Actually it can be simpler like
@psalm-param ('hello' | 'goodbye' | 1 | 2 | C::A)
or (necessarily without spaces)
@psalm-param 'hello'|'goodbye'|1|2|C::A

[nickyr]

@psalm-param 'hello'|'goodbye'|1|2|C::A

That's perfect

[muglug]

Merged basic support into master, will follow up with values-of/keys-of and class constant support at a later date.