Request failed SyntaxError: Unexpected token '<', "<br /> <b>"... is not valid JSON

[kkmuffme]

https://psalm.dev/r/e4eb7a3e05

Issue is from line 15, key-of<TMapping> seems to break it.

[psalm-github-bot]

I found these snippets:

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