Can't template based on the output of a pure function called on an input param

[jnvsor]

https://psalm.dev/r/9f37666cc3

ReflectionFunctionAbstract->isInternal is stubbed pure in psalm, but there's no way to template based on the output of it.

It would also be nice to be able to template based on arbitrary constructor assignments to uninitialized properties.

[psalm-github-bot]

I found these snippets:

https://psalm.dev/r/9f37666cc3

<?php

declare(strict_types=1);

/**
 * @psalm-template I of bool
 */
final readonly class DeclaredCallableBag
{
    /** @psalm-var I */
    public bool $internal;
    /** @psalm-var (I is true ? null : string) */
    public ?string $filename;
    /** @psalm-var (I is true ? null : int) */
    public ?int $startline;
    /** @psalm-var (I is true ? null : int) */
    public ?int $endline;

    public function __construct(ReflectionFunctionAbstract $callable)
    {
        $this->internal = $callable->isInternal();
        $t = $callable->getFileName();
        $this->filename = false === $t ? null : $t;
        $t = $callable->getStartLine();
        $this->startline = false === $t ? null : $t;
        $t = $callable->getEndLine();
        $this->endline = false === $t ? null : $t;
    }
}

Psalm output (using commit 03ee02c):

ERROR: InvalidPropertyAssignmentValue - 21:27 - $this->internal with declared type 'I:DeclaredCallableBag as bool' cannot be assigned type 'bool'