Flaw in the co-dependant variables types

[orklah]

In the example here: https://psalm.dev/r/9bc618221f

Psalm doesn't detect that $type_context can't be null because we're in a scope where $completion_data is null and we already stated that both can't be null.

Psalm manages to make it work if the conditional is outside the try/catch: https://psalm.dev/r/ab2b600564.

This is pretty low priority because it's an edge case of a complex module and the code, while correct, is a little confusing anyway.

Found by: #7247

[psalm-github-bot]

I found these snippets:

https://psalm.dev/r/9bc618221f

<?php
function scope(){
    try {
        $completion_data = getThingOrNullOrThrow();
    } catch (Exception $e) {
        return new stdClass();
    }

    try {
        $type_context = getThingOrNullOrThrow();
        if (!$completion_data && !$type_context) {
        	return new stdClass(); //HERE!
    	}
    } catch (Exception $e) {
        return new stdClass();
    }

    if ($completion_data) {
        // do something
    } else {
        /** @psalm-trace $type_context */
        // $type_context can't be null here or else we would have entered the conditional "HERE!" because both variables are false
    }
}

/** 
 * @return string|null
 * @throws Exception
 */
function getThingOrNullOrThrow(){
    
}

Psalm output (using commit 7b18673):

INFO: Trace - 22:0 - $type_context: null|string

INFO: MissingReturnType - 2:10 - Method scope does not have a return type, expecting null|stdClass

https://psalm.dev/r/ab2b600564

<?php
function scope(){
    try {
        $completion_data = getThingOrNullOrThrow();
    } catch (Exception $e) {
        return new stdClass();
    }

    try {
        $type_context = getThingOrNullOrThrow();
    } catch (Exception $e) {
        return new stdClass();
    }

    if (!$completion_data && !$type_context) {
        return new stdClass(); //HERE!
    }
    
    if ($completion_data) {
        // do something
    } else {
        /** @psalm-trace $type_context */
        // $type_context can't be null here or else we would have entered the conditional "HERE!" because both variables are false
    }
}

/** 
 * @return string|null
 * @throws Exception
 */
function getThingOrNullOrThrow(){
    
}

Psalm output (using commit 7b18673):

INFO: Trace - 23:0 - $type_context: non-falsy-string

INFO: MissingReturnType - 2:10 - Method scope does not have a return type, expecting null|stdClass

[weirdan]

Psalm now infers non-falsy-string for both snippets.