Literal 'foo' is not in string when using templated parameter types

[ciaranmcnulty]

https://psalm.dev/r/40d5f10df0

Here it's saying the string literal 'foo' doesn't match the templated type which is string - can't see anything wrong?

[psalm-github-bot]

I found these snippets:

https://psalm.dev/r/40d5f10df0

<?php

/** 
 * @template T
 */
interface Norm
{
    /**
     * @param T $input
     * @return T
     */
    public function normalize(mixed $input): mixed;   
}

/**
 * @implements Norm<string>
 */
class StringNorm implements Norm
{
    public function normalize(mixed $input): mixed
    {
        return strtolower($input);
    }
}

/**
 * @template TNorm
 *
 * @param TNorm $value
 * @param Norm<TNorm> $n
 */
function normalizeField(mixed $value, Norm $n): void
{
 	$n->normalize($value);
}

normalizeField('foo', new StringNorm());

Psalm output (using commit 7869cb5):

ERROR: InvalidArgument - 37:1 - Incompatible types found for TNorm ('foo' is not in string)

[danog]

Fixed by #8731