Handle BcMath\Number operators for simple cases

conf/config.neon

@@ -1053,6 +1053,10 @@ services:
 		arguments:
 			reportMagicProperties: %reportMagicProperties%
 			checkDynamicProperties: %checkDynamicProperties%
+	-
+		class: PHPStan\Type\Php\BcMathNumberOperatorTypeSpecifyingExtension
+		tags:
+			- phpstan.broker.operatorTypeSpecifyingExtension
 
 	-
 		class: PHPStan\Rules\Properties\UninitializedPropertyRule

src/Php/PhpVersion.php

@@ -400,4 +400,9 @@ public function substrReturnFalseInsteadOfEmptyString(): bool
 		return $this->versionId < 80000;
 	}
 
+	public function supportsBcMathNumberOperatorOverloading(): bool
+	{
+		return $this->versionId >= 80400;
+	}
+
 }

src/Reflection/InitializerExprTypeResolver.php

@@ -872,6 +872,11 @@ public function getModType(Expr $left, Expr $right, callable $getTypeCallback):
 			return $this->getNeverType($leftType, $rightType);
 		}
 
+		$extensionSpecified = $this->callOperatorTypeSpecifyingExtensions(new BinaryOp\Mod($left, $right), $leftType, $rightType);
+		if ($extensionSpecified !== null) {
+			return $extensionSpecified;
+		}
+
 		if ($leftType->toNumber() instanceof ErrorType || $rightType->toNumber() instanceof ErrorType) {
 			return new ErrorType();
 		}
@@ -1234,16 +1239,16 @@ public function getPowType(Expr $left, Expr $right, callable $getTypeCallback):
 		$leftType = $getTypeCallback($left);
 		$rightType = $getTypeCallback($right);
 
-		$exponentiatedTyped = $leftType->exponentiate($rightType);
-		if (!$exponentiatedTyped instanceof ErrorType) {
-			return $exponentiatedTyped;
-		}
-
 		$extensionSpecified = $this->callOperatorTypeSpecifyingExtensions(new BinaryOp\Pow($left, $right), $leftType, $rightType);
 		if ($extensionSpecified !== null) {
 			return $extensionSpecified;
 		}
 
+		$exponentiatedTyped = $leftType->exponentiate($rightType);
+		if (!$exponentiatedTyped instanceof ErrorType) {
+			return $exponentiatedTyped;
+		}
+
 		return new ErrorType();
 	}
 

src/Type/ObjectType.php

@@ -31,6 +31,8 @@
 use PHPStan\Reflection\Type\UnresolvedPropertyPrototypeReflection;
 use PHPStan\ShouldNotHappenException;
 use PHPStan\TrinaryLogic;
+use PHPStan\Type\Accessory\AccessoryNonEmptyStringType;
+use PHPStan\Type\Accessory\AccessoryNumericStringType;
 use PHPStan\Type\Constant\ConstantArrayType;
 use PHPStan\Type\Constant\ConstantBooleanType;
 use PHPStan\Type\Constant\ConstantStringType;
@@ -593,6 +595,14 @@ public function toFloat(): Type
 
 	public function toString(): Type
 	{
+		if ($this->isInstanceOf('BcMath\Number')->yes()) {
+			return new IntersectionType([
+				new StringType(),
+				new AccessoryNumericStringType(),
+				new AccessoryNonEmptyStringType(),
+			]);
+		}
+
 		$classReflection = $this->getClassReflection();
 		if ($classReflection === null) {
 			return new ErrorType();
@@ -678,7 +688,10 @@ public function toCoercedArgumentType(bool $strictTypes): Type
 
 	public function toBoolean(): BooleanType
 	{
-		if ($this->isInstanceOf('SimpleXMLElement')->yes()) {
+		if (
+			$this->isInstanceOf('SimpleXMLElement')->yes()
+			|| $this->isInstanceOf('BcMath\Number')->yes()
+		) {
 			return new BooleanType();
 		}
 

src/Type/Php/BcMathNumberOperatorTypeSpecifyingExtension.php

@@ -0,0 +1,53 @@
+<?php declare(strict_types = 1);
+
+namespace PHPStan\Type\Php;
+
+use PHPStan\Php\PhpVersion;
+use PHPStan\Type\ErrorType;
+use PHPStan\Type\NeverType;
+use PHPStan\Type\ObjectType;
+use PHPStan\Type\OperatorTypeSpecifyingExtension;
+use PHPStan\Type\Type;
+use function in_array;
+
+final class BcMathNumberOperatorTypeSpecifyingExtension implements OperatorTypeSpecifyingExtension
+{
+
+	public function __construct(private PhpVersion $phpVersion)
+	{
+	}
+
+	public function isOperatorSupported(string $operatorSigil, Type $leftSide, Type $rightSide): bool
+	{
+		if (!$this->phpVersion->supportsBcMathNumberOperatorOverloading() || $leftSide instanceof NeverType || $rightSide instanceof NeverType) {
+			return false;
+		}
+
+		$bcMathNumberType = new ObjectType('BcMath\Number');
+
+		return in_array($operatorSigil, ['-', '+', '*', '/', '**', '%'], true)
+			&& (
+				$bcMathNumberType->isSuperTypeOf($leftSide)->yes()
+				|| $bcMathNumberType->isSuperTypeOf($rightSide)->yes()
+			);
+	}
+
+	public function specifyType(string $operatorSigil, Type $leftSide, Type $rightSide): Type
+	{
+		$bcMathNumberType = new ObjectType('BcMath\Number');
+		$otherSide = $bcMathNumberType->isSuperTypeOf($leftSide)->yes()
+			? $rightSide
+			: $leftSide;
+
+		if (
+			$otherSide->isInteger()->yes()
+			|| $otherSide->isNumericString()->yes()
+			|| $bcMathNumberType->isSuperTypeOf($otherSide)->yes()
+		) {
+			return $bcMathNumberType;
+		}
+
+		return new ErrorType();
+	}
+
+}

tests/PHPStan/Analyser/NodeScopeResolverTest.php

@@ -196,6 +196,10 @@ private static function findTestFiles(): iterable
 			yield __DIR__ . '/../Rules/Comparison/data/bug-9499.php';
 		}
 
+		if (PHP_VERSION_ID >= 80400) {
+			yield __DIR__ . '/../Rules/Operators/data/bcmath-number.php';
+		}
+
 		yield __DIR__ . '/../Rules/PhpDoc/data/bug-8609-function.php';
 		yield __DIR__ . '/../Rules/Comparison/data/bug-5365.php';
 		yield __DIR__ . '/../Rules/Comparison/data/bug-6551.php';