Improve the method signature of Option::fromValue to better understand nullable/optional value

[ojhaujjwal]

When using Option::fromValue($something), psalm decoded it was Option<string | null> because $something is of type string | null.

This is the psalm error I got in my codebase:

However, I want to let psalm know that even if I pass something like null to Option::fromValue ,the output is actually only Option<string> instead of Option<string | null>.

[ojhaujjwal]

@schmittjoh It would be great if you could review this.

[GrahamCampbell]

Thanks for the PR. I tested this against current PHPStan and Psalm (both 5 and 6): the headline case still infers Option<string|null> when the value itself is string|null, since neither analyzer subtracts P when solving S from S|P, and the S|P parameter type makes the library's own PHPStan run fail because new Some($value) is now Some<S|P> rather than Some<S>. The improvement it does deliver, no longer widening the return type by the none value or the null default, is achieved more simply by typing $noneValue as mixed, which is under consideration in #63, so I'm closing this in favour of that approach.