Psalm does not derive correct element type of array shape member

[mstilkerich]

Hello,

after upgrading to psalm 5.11, I am getting a spurious error that did not occur with a previous 5.x version of psalm (unfortunately I do not know the exact version I used before, I think I upgraded last around January 2023).

I tried to condense the code snippet to something minimal:
https://psalm.dev/r/64389d2bd0

Inside the switch, psalm knows the value of $name an carries it as a string constant type. Therefore it should be able to know which member of the array shape is accessed when using $name as index, but apparently it does not. When I use the string literal as index instead (see second variant of the function), it works.

[psalm-github-bot]

I found these snippets:

https://psalm.dev/r/64389d2bd0

<?php

/**
 * @psalm-type PropTypes = array{
 *   'lkey'?: list<array{'content-type': string, version: string}>,
 *   'skey'?: string,
 * }
 */
class Test {
    /**
     * @psalm-var PropTypes
     */
    public $props = [];

    public function storeProperty(string $name): void
    {
        switch ($name) {
            case 'lkey':
                if (!isset($this->props[$name])) {
                    $this->props[$name] = [];
                }
                $addrData = [ 'content-type' => 'text/vcard', 'version' => '3.0' ];
                $this->props[$name][] = $addrData;
                break;
        }
    }
    
    public function storePropertyWorks(string $name): void
    {
        switch ($name) {
            case 'lkey':
                if (!isset($this->props[$name])) {
                    $this->props[$name] = [];
                }
                $addrData = [ 'content-type' => 'text/vcard', 'version' => '3.0' ];
                $this->props['lkey'][] = $addrData;
                break;
        }
    }
}

Psalm output (using commit 0221ff1):

ERROR: InvalidPropertyAssignmentValue - 23:17 - $this->props with declared type 'array{lkey?: list<array{'content-type': string, version: string}>, skey?: string}' cannot be assigned type 'array{lkey: list<array{'content-type': string, version: string}>|string, skey?: string}'

[robchett]

Tracked the regression down to 2327917, a fix for #9433

[orklah]

@ptomulik if you're able to take a look, it would be very helpful :)

[ptomulik]

I guess, we shall start from here: #9439 (comment)

[ptomulik]

Found another variant for this bug, but this time it seems to be independent of 2327917:

https://psalm.dev/r/338c7bae15

[psalm-github-bot]

I found these snippets:

https://psalm.dev/r/338c7bae15

<?php

/**
 * @psalm-type PropTypes = array{
 *   lkey?: list<array{'content-type': string, version: string}>,
 *   skey?: string,
 * }
 */
class Test {
    /**
     * @psalm-var PropTypes
     */
    public $props = [];

    public function storeProperty(string $name): void
    {
        switch ($name) {
            case 'lkey':
                if (!isset($this->props[$name])) { }
                $addrData = [ 'content-type' => 'text/vcard', 'version' => '3.0' ];
                $this->props[$name][] = $addrData;
                break;
        }
    }

    public function storePropertyWorks(string $name): void
    {
        switch ($name) {
            case 'lkey':
                $addrData = [ 'content-type' => 'text/vcard', 'version' => '3.0' ];
                $this->props[$name][] = $addrData;
                break;
        }
    }
}

Psalm output (using commit 24168f6):

ERROR: InvalidPropertyAssignmentValue - 21:17 - $this->props with declared type 'array{lkey?: list<array{'content-type': string, version: string}>, skey?: string}' cannot be assigned type 'array{lkey: list<array{'content-type': string, version: string}>|string, skey?: string}'

[ptomulik]

This gets more and more interesting, deleted skey from the previous example and the error has gone

https://psalm.dev/r/5223e6b4cd

now get it back, but change the, seeminly unrelated skey type to, let it be, int, one error turned into two

https://psalm.dev/r/1e02b68bcd

looks like types from different keys of array interfere here, reverting 2327917 doesn't help

can anyone explain? @orklah, @robchett?

[psalm-github-bot]

I found these snippets:

https://psalm.dev/r/5223e6b4cd

<?php

/**
 * @psalm-type PropTypes = array{
 *   lkey?: list<array{'content-type': string, version: string}>,
 * }
 */
class Test {
    /**
     * @psalm-var PropTypes
     */
    public $props = [];

    public function storeProperty(string $name): void
    {
        switch ($name) {
            case 'lkey':
                if (!isset($this->props[$name])) { }
                $addrData = [ 'content-type' => 'text/vcard', 'version' => '3.0' ];
                $this->props[$name][] = $addrData;
                break;
        }
    }

    public function storePropertyWorks(string $name): void
    {
        switch ($name) {
            case 'lkey':
                $addrData = [ 'content-type' => 'text/vcard', 'version' => '3.0' ];
                $this->props[$name][] = $addrData;
                break;
        }
    }
}

Psalm output (using commit 24168f6):

No issues!

https://psalm.dev/r/1e02b68bcd

<?php

/**
 * @psalm-type PropTypes = array{
 *   lkey?: list<array{'content-type': string, version: string}>,
 *   skey?: int
 * }
 */
class Test {
    /**
     * @psalm-var PropTypes
     */
    public $props = [];

    public function storeProperty(string $name): void
    {
        switch ($name) {
            case 'lkey':
                if (!isset($this->props[$name])) { }
                $addrData = [ 'content-type' => 'text/vcard', 'version' => '3.0' ];
                $this->props[$name][] = $addrData;
                break;
        }
    }

    public function storePropertyWorks(string $name): void
    {
        switch ($name) {
            case 'lkey':
                $addrData = [ 'content-type' => 'text/vcard', 'version' => '3.0' ];
                $this->props[$name][] = $addrData;
                break;
        }
    }
}

Psalm output (using commit 24168f6):

ERROR: PossiblyInvalidArrayAssignment - 21:17 - Cannot access array value on non-array variable $this->props[$name] of type int

ERROR: InvalidPropertyAssignmentValue - 21:17 - $this->props with declared type 'array{lkey?: list<array{'content-type': string, version: string}>, skey?: int}' cannot be assigned type 'array{lkey: int|list<array{'content-type': string, version: string}>, skey?: int}'

[ptomulik]

Possibly my PR #9439 didn't fix issue, just turned false-negatives into false positives, looks like #9433 is still here.

[ptomulik]

$this->props[$name] vs $this->props[$name . '']

https://psalm.dev/r/1149743dfb

[psalm-github-bot]

I found these snippets:

https://psalm.dev/r/1149743dfb

<?php

/**
 * @psalm-type PropTypes = array{
 *   lkey?: list<array{'content-type': string, version: string}>,
 *   skey?: int
 * }
 */
class Test {
    /**
     * @psalm-var PropTypes
     */
    public $props = [];

    public function storeProperty(string $name): void
    {
        switch ($name) {
            case 'lkey':
                if (!isset($this->props[$name])) { }
                $addrData = [ 'content-type' => 'text/vcard', 'version' => '3.0' ];
                $this->props[$name . ''][] = $addrData;
                $this->props[$name][] = $addrData;
                break;
        }
    }
}

Psalm output (using commit 24168f6):

ERROR: PossiblyInvalidArrayAssignment - 22:17 - Cannot access array value on non-array variable $this->props[$name] of type int

ERROR: InvalidPropertyAssignmentValue - 22:17 - $this->props with declared type 'array{lkey?: list<array{'content-type': string, version: string}>, skey?: int}' cannot be assigned type 'array{lkey: int|list<array{'content-type': string, version: string}>, skey?: int}'