multiply by zero is always zero

Author: staabm

src/Analyser/MutatingScope.php

@@ -1040,6 +1040,34 @@ private function resolveType(Expr $node): Type
 return new StringType();
 }
 
+if (
+$node instanceof Node\Expr\BinaryOp\Mul
+|| $node instanceof Node\Expr\AssignOp\Mul
+) {
+if ($node instanceof Node\Expr\AssignOp) {
+$leftType = $this->getType($node->var)->toNumber();
+$rightType = $this->getType($node->expr)->toNumber();
+} else {
+$leftType = $this->getType($node->left)->toNumber();
+$rightType = $this->getType($node->right)->toNumber();
+}
+
+$floatType = new FloatType();
+
+if ($leftType instanceof ConstantIntegerType && $leftType->getValue() === 0) {
+if ($floatType->isSuperTypeOf($rightType)->yes()) {
+return new ConstantFloatType(0.0);
+}
+return new ConstantIntegerType(0);
+}
+if ($rightType instanceof ConstantIntegerType && $rightType->getValue() === 0) {
+if ($floatType->isSuperTypeOf($leftType)->yes()) {
+return new ConstantFloatType(0.0);
+}
+return new ConstantIntegerType(0);
+}
+}
+
 if (
 $node instanceof Node\Expr\BinaryOp\Div
 || $node instanceof Node\Expr\AssignOp\Div

tests/PHPStan/Analyser/data/math.php

@@ -109,4 +109,34 @@ public function doSit(int $i, int $j): void
 assertType('int', $i - $j);
 }
 
+/**
+ * @param int<-5, 5> $range
+ */
+public function multiplyZero(int $i, float $f, $range): void
+{
+assertType('0', $i * false);
+assertType('0.0', $f * false);
+assertType('0', $range * false);
+
+assertType('0', $i * '0');
+assertType('0.0', $f * '0');
+assertType('0', $range * '0');
+
+assertType('0', $i * 0);
+assertType('0.0', $f * 0);
+assertType('0', $range * 0);
+
+assertType('0', 0 * $i);
+assertType('0.0', 0 * $f);
+assertType('0', 0 * $range);
+
+$i *= 0;
+$f *= 0;
+$range *= 0;
+assertType('0', $i);
+assertType('0.0', $f);
+assertType('0', $range);
+
+}
+
 }