Add GMP unary operator type specifying extension

Implements UnaryOperatorTypeSpecifyingExtension for GMP to handle
unary minus (-), unary plus (+), and bitwise NOT (~) operators.

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

Author: Firehed

src/Type/Php/GmpUnaryOperatorTypeSpecifyingExtension.php

@@ -0,0 +1,35 @@
+<?php declare(strict_types = 1);
+
+namespace PHPStan\Type\Php;
+
+use PHPStan\DependencyInjection\AutowiredService;
+use PHPStan\Type\NeverType;
+use PHPStan\Type\ObjectType;
+use PHPStan\Type\Type;
+use PHPStan\Type\UnaryOperatorTypeSpecifyingExtension;
+use function in_array;
+
+#[AutowiredService]
+final class GmpUnaryOperatorTypeSpecifyingExtension implements UnaryOperatorTypeSpecifyingExtension
+{
+
+	public function isOperatorSupported(string $operatorSigil, Type $operand): bool
+	{
+		if ($operand instanceof NeverType) {
+			return false;
+		}
+
+		if (!in_array($operatorSigil, ['-', '+', '~'], true)) {
+			return false;
+		}
+
+		$gmpType = new ObjectType('GMP');
+		return $gmpType->isSuperTypeOf($operand)->yes();
+	}
+
+	public function specifyType(string $operatorSigil, Type $operand): Type
+	{
+		return new ObjectType('GMP');
+	}
+
+}