Is T[K] broken now?

[zerkms]

Example from the documentation: https://psalm.dev/docs/annotating_code/type_syntax/utility_types/#tk

https://psalm.dev/r/be7148dbb1

[psalm-github-bot]

I found these snippets:

https://psalm.dev/r/be7148dbb1

<?php

/**
 * @template T of array
 * @template TKey of string
 * @param T $arr
 * @param TKey $k
 * @return T[TKey]
 */
function a(array $arr, string $k): mixed {
  assert(isset($arr[$k]));
  return $arr[$k];
}

$a = a(['test' => 123], 'test');
/** @psalm-trace $a */; // 123

Psalm output (using commit b99857c):

INFO: MixedReturnStatement - 12:10 - Could not infer a return type

INFO: MixedInferredReturnType - 8:12 - Could not verify return type 'T[TKey]' for a

INFO: Trace - 16:23 - $a: 123

INFO: UnusedVariable - 15:1 - $a is never referenced or the value is not used

[orklah]

Well, it seems to work but Mixed* issues happens. We should try to get rid of those

[kkmuffme]

It doesn't work here too? https://psalm.dev/r/3d33f66c11

(like https://psalm.dev/r/e4eb7a3e05 doesn't work either but there seems to be a separate bug psalm/psalm.dev#98)

[psalm-github-bot]

I found these snippets:

https://psalm.dev/r/3d33f66c11

<?php

class QueryDB {}

class Compatibility {}

class DI {
   const MAPPING = array(
		'query' => QueryDB::class,
       	'comp' => Compatibility::class,
   );
    
   /**
    * @template TMapping of DI::MAPPING
    * @template TKey of key-of<DI::MAPPING>
    *
    * @param TKey $arg
    * @return TMapping[TKey]
    */
   public function get( $arg ) {
       $v = self::MAPPING[ $arg ];
       /** @psalm-trace $v */;
       return $v;
   }
}

$d = new DI();
$r = $d->get( 'comp' );
$c = new $r();
/** @psalm-trace $c */;

Psalm output (using commit 106b986):

INFO: MixedAssignment - 28:1 - Unable to determine the type that $r is being assigned to

INFO: MixedMethodCall - 29:6 - Cannot call constructor on an unknown class

INFO: Trace - 30:23 - $c: object

INFO: UnusedVariable - 29:1 - $c is never referenced or the value is not used

INFO: Trace - 22:30 - $v: Compatibility::class|QueryDB::class

ERROR: InvalidReturnStatement - 23:15 - The inferred type 'Compatibility::class|QueryDB::class' does not match the declared return type 'TMapping[TKey]' for DI::get

ERROR: InvalidReturnType - 18:15 - The declared return type 'TMapping[TKey]' for DI::get is incorrect, got 'Compatibility::class|QueryDB::class'

https://psalm.dev/r/e4eb7a3e05

<?php

class QueryDB {}

class Compatibility {}

class DI {
   const MAPPING = array(
		'query' => QueryDB::class,
       	'comp' => Compatibility::class,
   );
    
   /**
    * @template TMapping of DI::MAPPING
    * @template TKey of key-of<TMapping>
    *
    * @param TKey $arg
    * @return TMapping[TKey]
    */
   public function get( $arg ) {
       $v = self::MAPPING[ $arg ];
       /** @psalm-trace $v */;
       return $v;
   }
}

$d = new DI();
$r = $d->get( 'comp' );
$c = new $r();
/** @psalm-trace $c */;

Psalm encountered an internal error:

/vendor/vimeo/psalm/src/Psalm/Internal/Type/TemplateStandinTypeReplacer.php: count(): Argument #1 ($value) must be of type Countable|array, null given