InvalidReturnType due to void and null not treated the same

[kkmuffme]

https://psalm.dev/r/f4bb991d20

void and null must be treated as the same thing.

[psalm-github-bot]

I found these snippets:

https://psalm.dev/r/f4bb991d20

<?php

/**
 * @return void|never
 */
function foo() {
    if ( rand( 0, 10 ) > 5 ) {
        return;
    }    
}

Psalm output (using commit 8b7bc07):

ERROR: InvalidReturnType - 4:12 - The declared return type 'null' for foo is incorrect, got 'void'

[AndrolGenhald]

Hmmm, I don't think it actually makes sense to have a return type of void|never. Regardless though, that error is incredibly misleading.

[orklah]

Hmmm, I don't think it actually makes sense to have a return type of void|never. Regardless though, that error is incredibly misleading.

It can make sense for assertions methods where you either throw or do nothing. but the snippet in example doesn't do that. So yeah, it's just a wrong phrasing

[AndrolGenhald]

It can make sense for assertions methods where you either throw or do nothing.

Shouldn't that just combine to void though? never is the bottom type, so it's a subtype of all other types, so if you do x|never it should just simplify to x.

[orklah]

True. The case I had some times ago was something like ($die_on_redirect is true ? never : void). So technically it's the same case but the combination doesn't happen

[AndrolGenhald]

The case I had some times ago was something like ($die_on_redirect is true ? never : void).

Ahh, yeah I could see that then. Interestingly though, this actually works fine while this doesn't.

[psalm-github-bot]

I found these snippets:

https://psalm.dev/r/8dad765588

<?php

/**
 * @return ($bar is true ? void : never)
 */
function foo(bool $bar) {
    if ($bar) {
        return;
    }
    
    exit;    
}

Psalm output (using commit 8b7bc07):

No issues!

https://psalm.dev/r/d162606c86

<?php

/**
 * @return void|never
 */
function foo(bool $bar) {
    if ($bar) {
        return;
    }
    
    exit;    
}

Psalm output (using commit 8b7bc07):

ERROR: InvalidReturnType - 4:12 - The declared return type 'null' for foo is incorrect, got 'void'