Merge pull request #16 from simPod/narrow-int-arithmetic-rounding

Author: simPod

money/src/MoneyOperationThrowTypeExtension.php

@@ -182,6 +182,11 @@ private function narrowArithmetic(
             return $methodReflection->getThrowType();
         }
 
+        // For plus/minus/multipliedBy with int arg, rounding is impossible:
+        // int arithmetic on a Money value always produces an exact result
+        // that fits the same context (any scale, any step).
+        $intArgSuppressesRounding = $methodName !== 'dividedBy' && SafeType::isInteger($argType);
+
         // Money: build residual throw types.
         $residualTypes = [];
 
@@ -195,8 +200,8 @@ private function narrowArithmetic(
             $residualTypes[] = new ObjectType(NumberFormatException::class);
         }
 
-        // RoundingNecessaryException when rounding mode is not safe.
-        if (! $roundingModeIsSafe) {
+        // RoundingNecessaryException when rounding mode is not safe and int arg doesn't suppress it.
+        if (! $roundingModeIsSafe && ! $intArgSuppressesRounding) {
             $residualTypes[] = new ObjectType(RoundingNecessaryException::class);
         }
 

money/src/SafeType.php

@@ -80,6 +80,17 @@ public static function isSafeRoundingMode(Type $type): bool
         return $unnecessaryType->isSuperTypeOf($type)->no();
     }
 
+    /**
+     * Returns whether the given type is an integer.
+     *
+     * Integer arithmetic (plus, minus, multipliedBy) on Money always produces
+     * an exact result that fits the same context, so rounding cannot occur.
+     */
+    public static function isInteger(Type $type): bool
+    {
+        return (new IntegerType())->isSuperTypeOf($type)->yes();
+    }
+
     /**
      * Returns whether the given type is guaranteed to be zero.
      *

money/tests/data/MoneyThrowTypes.php

@@ -212,6 +212,53 @@ public function dividedByWithUnnecessaryRounding(Money $a): void
         }
     }
 
+    // --- Int arithmetic (no rounding mode needed) ---
+
+    public function multipliedByInt(Money $a): void
+    {
+        try {
+            $result = $a->multipliedBy(5);
+        } finally {
+            assertVariableCertainty(TrinaryLogic::createYes(), $result);
+        }
+    }
+
+    public function plusWithInt(Money $a): void
+    {
+        try {
+            $result = $a->plus(10);
+        } finally {
+            assertVariableCertainty(TrinaryLogic::createYes(), $result);
+        }
+    }
+
+    public function minusWithInt(Money $a): void
+    {
+        try {
+            $result = $a->minus(10);
+        } finally {
+            assertVariableCertainty(TrinaryLogic::createYes(), $result);
+        }
+    }
+
+    public function dividedByIntNoRoundingMode(Money $a): void
+    {
+        try {
+            $result = $a->dividedBy(3);
+        } finally {
+            assertVariableCertainty(TrinaryLogic::createMaybe(), $result);
+        }
+    }
+
+    public function multipliedByString(Money $a, string $s): void
+    {
+        try {
+            $result = $a->multipliedBy($s);
+        } finally {
+            assertVariableCertainty(TrinaryLogic::createMaybe(), $result);
+        }
+    }
+
     // --- RationalMoney arithmetic ---
 
     public function rationalPlusWithInt(RationalMoney $a): void