Allow GMP and BCMath\Number in arithmetic operations

src/Rules/Operators/OperatorRuleHelper.php

@@ -3,6 +3,7 @@
 namespace PHPStan\Rules\Operators;
 
 use PhpParser\Node\Expr;
+use PhpParser\Node\Scalar\Int_;
 use PHPStan\Analyser\Scope;
 use PHPStan\Rules\RuleLevelHelper;
 use PHPStan\Type\Accessory\AccessoryNumericStringType;
@@ -38,7 +39,20 @@ public function isValidForArithmeticOperation(Scope $scope, Expr $expr): bool
 			return true;
 		}
 
-		return $this->isSubtypeOfNumber($scope, $expr);
+		if ($this->isSubtypeOfNumber($scope, $expr)) {
+			return true;
+		}
+
+		// Check if the type supports arithmetic via operator overloading extensions
+		// (only applies to object types like GMP, BCMath\Number)
+		if ($type->isObject()->yes()) {
+			$resultType = $scope->getType(new Expr\BinaryOp\Plus($expr, new Int_(1)));
+			if (!$resultType instanceof ErrorType) {
+				return true;
+			}
+		}
+
+		return false;
 	}
 
 	public function isValidForIncrement(Scope $scope, Expr $expr): bool
@@ -53,7 +67,18 @@ public function isValidForIncrement(Scope $scope, Expr $expr): bool
 			return true;
 		}
 
-		return $this->isSubtypeOfNumber($scope, $expr);
+		if ($this->isSubtypeOfNumber($scope, $expr)) {
+			return true;
+		}
+
+		if ($type->isObject()->yes()) {
+			$resultType = $scope->getType(new Expr\PostInc($expr));
+			if (!$resultType instanceof ErrorType) {
+				return true;
+			}
+		}
+
+		return false;
 	}
 
 	public function isValidForDecrement(Scope $scope, Expr $expr): bool
@@ -63,7 +88,18 @@ public function isValidForDecrement(Scope $scope, Expr $expr): bool
 			return true;
 		}
 
-		return $this->isSubtypeOfNumber($scope, $expr);
+		if ($this->isSubtypeOfNumber($scope, $expr)) {
+			return true;
+		}
+
+		if ($type->isObject()->yes()) {
+			$resultType = $scope->getType(new Expr\PostDec($expr));
+			if (!$resultType instanceof ErrorType) {
+				return true;
+			}
+		}
+
+		return false;
 	}
 
 	private function isSubtypeOfNumber(Scope $scope, Expr $expr): bool

tests/Rules/Operators/OperandInArithmeticPostDecrementRuleTest.php

@@ -23,23 +23,23 @@ protected function getExpectedErrors(): array
 		return [
 			[
 				'Only numeric types are allowed in post-decrement, false given.',
-				21,
+				25,
 			],
 			[
 				'Only numeric types are allowed in post-decrement, string given.',
-				22,
+				26,
 			],
 			[
 				'Only numeric types are allowed in post-decrement, null given.',
-				23,
+				27,
 			],
 			[
 				'Only numeric types are allowed in post-decrement, stdClass given.',
-				24,
+				28,
 			],
 			[
 				'Only numeric types are allowed in post-decrement, int|stdClass|string given.',
-				26,
+				30,
 			],
 		];
 	}

tests/Rules/Operators/OperandInArithmeticPostIncrementRuleTest.php

@@ -23,19 +23,19 @@ protected function getExpectedErrors(): array
 		return [
 			[
 				'Only numeric types are allowed in post-increment, false given.',
-				32,
+				38,
 			],
 			[
 				'Only numeric types are allowed in post-increment, null given.',
-				34,
+				40,
 			],
 			[
 				'Only numeric types are allowed in post-increment, stdClass given.',
-				35,
+				41,
 			],
 			[
 				'Only numeric types are allowed in post-increment, int|stdClass|string given.',
-				37,
+				43,
 			],
 		];
 	}

tests/Rules/Operators/OperandInArithmeticPreDecrementRuleTest.php

@@ -23,23 +23,23 @@ protected function getExpectedErrors(): array
 		return [
 			[
 				'Only numeric types are allowed in pre-decrement, false given.',
-				43,
+				51,
 			],
 			[
 				'Only numeric types are allowed in pre-decrement, string given.',
-				44,
+				52,
 			],
 			[
 				'Only numeric types are allowed in pre-decrement, null given.',
-				45,
+				53,
 			],
 			[
 				'Only numeric types are allowed in pre-decrement, stdClass given.',
-				46,
+				54,
 			],
 			[
 				'Only numeric types are allowed in pre-decrement, int|stdClass|string given.',
-				48,
+				56,
 			],
 		];
 	}

tests/Rules/Operators/OperandInArithmeticPreIncrementRuleTest.php

@@ -23,19 +23,19 @@ protected function getExpectedErrors(): array
 		return [
 			[
 				'Only numeric types are allowed in pre-increment, false given.',
-				54,
+				64,
 			],
 			[
 				'Only numeric types are allowed in pre-increment, null given.',
-				56,
+				66,
 			],
 			[
 				'Only numeric types are allowed in pre-increment, stdClass given.',
-				57,
+				67,
 			],
 			[
 				'Only numeric types are allowed in pre-increment, int|stdClass|string given.',
-				59,
+				69,
 			],
 		];
 	}

tests/Rules/Operators/OperandInArithmeticUnaryMinusRuleTest.php

@@ -31,4 +31,9 @@ public function testRule(): void
 		]);
 	}
 
+	public function testOperatorOverloads(): void
+	{
+		$this->analyse([__DIR__ . '/data/operator-overloads.php'], []);
+	}
+
 }

tests/Rules/Operators/OperandInArithmeticUnaryPlusRuleTest.php

@@ -31,4 +31,9 @@ public function testRule(): void
 		]);
 	}
 
+	public function testOperatorOverloads(): void
+	{
+		$this->analyse([__DIR__ . '/data/operator-overloads.php'], []);
+	}
+
 }

tests/Rules/Operators/OperandsInArithmeticAdditionRuleTest.php

@@ -60,4 +60,9 @@ public function testRule(): void
 		$this->analyse([__DIR__ . '/data/operators.php'], $messages);
 	}
 
+	public function testOperatorOverloads(): void
+	{
+		$this->analyse([__DIR__ . '/data/operator-overloads.php'], []);
+	}
+
 }

tests/Rules/Operators/OperandsInArithmeticDivisionRuleTest.php

@@ -43,4 +43,9 @@ public function testRule(): void
 		]);
 	}
 
+	public function testOperatorOverloads(): void
+	{
+		$this->analyse([__DIR__ . '/data/operator-overloads.php'], []);
+	}
+
 }

tests/Rules/Operators/OperandsInArithmeticExponentiationRuleTest.php

@@ -43,4 +43,9 @@ public function testRule(): void
 		]);
 	}
 
+	public function testOperatorOverloads(): void
+	{
+		$this->analyse([__DIR__ . '/data/operator-overloads.php'], []);
+	}
+
 }

tests/Rules/Operators/OperandsInArithmeticModuloRuleTest.php

@@ -43,4 +43,9 @@ public function testRule(): void
 		]);
 	}
 
+	public function testOperatorOverloads(): void
+	{
+		$this->analyse([__DIR__ . '/data/operator-overloads.php'], []);
+	}
+
 }

tests/Rules/Operators/OperandsInArithmeticMultiplicationRuleTest.php

@@ -43,4 +43,9 @@ public function testRule(): void
 		]);
 	}
 
+	public function testOperatorOverloads(): void
+	{
+		$this->analyse([__DIR__ . '/data/operator-overloads.php'], []);
+	}
+
 }

tests/Rules/Operators/OperandsInArithmeticSubtractionRuleTest.php

@@ -43,4 +43,9 @@ public function testRule(): void
 		]);
 	}
 
+	public function testOperatorOverloads(): void
+	{
+		$this->analyse([__DIR__ . '/data/operator-overloads.php'], []);
+	}
+
 }

tests/Rules/Operators/data/increment-decrement.php

@@ -2,6 +2,8 @@
 
 namespace Operators;
 
+use BcMath\Number;
+use GMP;
 use stdClass;
 
 $int = 123;
@@ -14,8 +16,10 @@
 $mixed = foo();
 /** @var int|string|stdClass $union */
 $union = bar();
+$gmp = new GMP('1');
+$bcmath = new BCMath\Number('2');
 
-(function () use ($int, $float, $bool, $string, $null, $object, $mixed, $union): void {
+(function () use ($int, $float, $bool, $string, $null, $object, $mixed, $union, $gmp, $bcmath): void {
 	$int--;
 	$float--;
 	$bool--;
@@ -24,9 +28,11 @@
 	$object--;
 	$mixed--;
 	$union--;
+	$gmp--;
+	$bcmath--;
 })();
 
-(function () use ($int, $float, $bool, $string, $null, $object, $mixed, $union): void {
+(function () use ($int, $float, $bool, $string, $null, $object, $mixed, $union, $gmp, $bcmath): void {
 	$int++;
 	$float++;
 	$bool++;
@@ -35,9 +41,11 @@
 	$object++;
 	$mixed++;
 	$union++;
+	$gmp++;
+	$bcmath++;
 })();
 
-(function () use ($int, $float, $bool, $string, $null, $object, $mixed, $union): void {
+(function () use ($int, $float, $bool, $string, $null, $object, $mixed, $union, $gmp, $bcmath): void {
 	--$int;
 	--$float;
 	--$bool;
@@ -46,9 +54,11 @@
 	--$object;
 	--$mixed;
 	--$union;
+	--$gmp;
+	--$bcmath;
 })();
 
-(function () use ($int, $float, $bool, $string, $null, $object, $mixed, $union): void {
+(function () use ($int, $float, $bool, $string, $null, $object, $mixed, $union, $gmp, $bcmath): void {
 	++$int;
 	++$float;
 	++$bool;
@@ -57,6 +67,8 @@
 	++$object;
 	++$mixed;
 	++$union;
+	++$gmp;
+	++$bcmath;
 })();