handle basic operator usage with BcMath\Number

Author: schlndh

conf/config.neon

@@ -1047,6 +1047,10 @@ services:
 		arguments:
 			reportMagicProperties: %reportMagicProperties%
 			checkDynamicProperties: %checkDynamicProperties%
+	-
+		class: PHPStan\Type\Php\BcMathNumberOperatorTypeSpecifyingExtension
+		tags:
+			- phpstan.broker.operatorTypeSpecifyingExtension
 
 	-
 		class: PHPStan\Rules\Properties\UninitializedPropertyRule

src/Php/PhpVersion.php

@@ -395,4 +395,9 @@ 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/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();
+	}
+
+}