Feature/variadic union type improvemence

[nzour]

#183

Changelog

• function Psl\Type\union now takes variadic third parameter
• function Psl\Type\union arguments $left_type and $right_type were renamed to $first and $second
  This is a breaking change, because if somebody uses PHP8+ and does
  union(left_type: $left, right_type: $right) - this would trigger runtime Error.

Future scope

• I think we should use @no-named-arguments psalm's annotation
  I haven't used this in my PR, cause I think it should be discussed and (if accepted) added atomically for all possible functions and methods
• As @azjezz mentioned in Union for variadic types #183, we should also make variadic function Psl\Type\intersection

[nzour]

I think I've chosen wrong branch to merge to. @azjezz do you have 2.0 branch?

[azjezz]

As mentioned in the issue, renaming parameters is not considered a BC break ( for me ), we can merge this into 1.7

[azjezz]

@zour228 can you apply the same change to intersection? I think these two should stay consistent with each other.

[nzour]

@zour228 can you apply the same change to intersection? I think these two should stay consistent with each other.

Sure, but maybe next day, it's late time on my watch

[nzour]

About named parameters and BC:
I still think it's important to mention parameters renaming in changelog.
To prevent unexpected error that somebody may have

[nzour]

@azjezz didn't know that psalm has an issues with intersection types (even with such a simple example)
https://psalm.dev/r/737e004fcd

Therefore the following example have type inference issues too:

$first = shape(['first' => string()]);
$second = shape(['second' => string()]);

$res = intersection($first, $second);
// inferred type of $res is TypeInterface<array{first: string}>
// but I was expecting TypeInterface<array{first: string, second: string}>

So, I am not sure if I know hot to implement function with variadic parameters.
But maybe type inference is not main feature here?

[psalm-github-bot]

I found these snippets:

https://psalm.dev/r/737e004fcd

<?php

/**
 * @template Tf
 * @template Ts
 *
 * @param Tf $first
 * @param Ts $second
 *
 * @return Tf&Ts
 */
function intersection(
    mixed $first,
    mixed $second
): mixed {
    throw new RuntimeException();
}


$first = ['f' => 1];
$second = ['s' => 2];

/** @psalm-trace $result1 */
$result1 = intersection($first, $second);

/** @psalm-trace $result2 */
$result2 = intersection($second, $first);

Psalm output (using commit 698adef):

INFO: Trace - 24:1 - $result1: array{f: 1}

INFO: Trace - 27:1 - $result2: array{s: 2}

[azjezz]

Intersection types work only with objects

[coveralls]

Pull Request Test Coverage Report for Build 787060807

• 5 of 5 (100.0%) changed or added relevant lines in 2 files are covered.
• No unchanged relevant lines lost coverage.
• Overall coverage remained the same at 100.0%

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Totals
Change from base Build 744011924:	0.0%
Covered Lines:	2985
Relevant Lines:	2985

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💛 - Coveralls

[azjezz]

LGTM, you can send a separate PR for intersection types later on.

Thank you 🎉