ltrim(class-string, '\\') should return a class-string

[Tofandel]

When using

    /**
     * Removes the prepended backslash of a class string to conform with how php outputs class names
     *
     * @psalm-param class-string $className
     *
     * @psalm-return class-string
     */
    function normalizeClassName(string $className): string
    {
        return ltrim($className, '\\');
    }

2 errors will be thrown

ERROR: MoreSpecificReturnType - The declared return type 'class-string' for normalizeClassName is more specific than the inferred return type 'string' (see https://psalm.dev/070)
     * @psalm-return class-string

ERROR: LessSpecificReturnStatement - The type 'string' is more general than the declared return type 'class-string' for normalizeClassName (see https://psalm.dev/129)
        return ltrim($className, '\\');

It would be a nice addition to avoid this false negatives as this specific ltrim of a class string will always result in the same class-string being returned

Psalm should detect this very specific ltrim call if the input is a class-string and in that case infer a class-string type instead of a string

This issue also exists for phpstan phpstan/phpstan#7483

[Tofandel]

https://psalm.dev/r/b6ecdc9b09

[psalm-github-bot]

I found these snippets:

https://psalm.dev/r/b6ecdc9b09

<?php

/**
  * Removes the prepended backslash of a class string to conform with how php outputs class names
  *
  * @psalm-param class-string $className
  *
  * @psalm-return class-string
  */
function normalizeClassName(string $className): string
{
    return ltrim($className, '\\');
}

Psalm output (using commit fbd240b):

INFO: LessSpecificReturnStatement - 12:12 - The type 'string' is more general than the declared return type 'class-string' for normalizeClassName

INFO: MoreSpecificReturnType - 8:19 - The declared return type 'class-string' for normalizeClassName is more specific than the inferred return type 'string'

[Tofandel]

I have very little knowledge of the inner working of psalm, but would 4.x...Tofandel:psalm:patch-1
do the trick?

Or is something like this possible:
@return ($string is class-string ? ( $characters is '\\' ? class-string : string ) : string )

Edit:
Gave it a try, works flawlessly