System error: "leaveNode() returned invalid value of type integer" about rector HOT 3 CLOSED

That's expected, you can't use NodeTraverser::REMOVE_NODE directly under refactor() on Expr, you need to remove the whole Expression stmt, something like:

	public function getNodeTypes(): array {
		return [
			Node\Stmt\Expression::class
		];
	}

	public function refactor(Node $node) {
            if ($node->expr instanceof Node\Expr\ErrorSuppress && $node->expr->expr instanceof Include_) {
    		return NodeTraverser::REMOVE_NODE;
            }

            if ($node->expr instanceof Include_) {
    		return NodeTraverser::REMOVE_NODE;
            }
        
            return null;
	}

that already answered at #8172

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Thank you! Is it defined somewhere in the documentation? I cannot find this

from rector.

It's inherited treat of AST tree, so I'd look for it somewhere in:
https://github.com/nikic/PHP-Parser/tree/4.x/doc

Still, we might add a "AST Gotchas" page to our docs, as this is something hard to find.
Where would you expect this to find?

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