DisallowedEmptyRuleFixerRector misbehaves, it converts !empty(string|null $foo) to $foo !== null

[janedbal]

Bug Report

Subject	Details
Rector version	dev-main

DisallowedEmptyRuleFixerRector is making dangerous non-equivalent changes. See snippet below.

Minimal PHP Code Causing Issue

class Bug {
	public function get(): ?string {
		return null;
	}

	public function example(): void {
		if (!empty($this->get())) {
			
		}
	}
}
// gets converted to
class Bug {
	public function get(): ?string {
		return null;
	}

	public function example(): void {
		if ($this->get() !== null) {
			
		}
	}
}

Expected Behaviour

// should be converted to
class Bug {
	public function get(): ?string {
		return null;
	}

	public function example(): void {
		if ($this->get() !== null && $this->get() !== '') {
			
		}
	}
}

[janedbal]

Other strict rules have similar issue. E.g.

public function example(?string $foo): void {
    if ($foo) {} // gets converted to $foo !== null
}

[TomasVotruba]

Issue is better, thanks 👍

Ref https://twitter.com/janedbal/status/1445342334036725762
Makes sense!

[TomasVotruba]

Fixed with opt-in empty scalars in rectorphp/rector-src#956