Fixed InterRangeType multiplication/division of maximas by a negative constant

Author: staabm

src/Analyser/MutatingScope.php

@@ -1021,12 +1021,7 @@ private function resolveType(Expr $node): Type
 			}
 
 			if ($type instanceof IntegerRangeType) {
-				$negativeRange = $this->resolveType(new Node\Expr\BinaryOp\Mul($node->expr, new LNumber(-1)));
-
-				if ( $negativeRange instanceof IntegerRangeType && ($negativeRange->getMin() === null || $negativeRange->getMax() === null)) {
-					return IntegerRangeType::fromInterval($negativeRange->getMax(), $negativeRange->getMin());
-				}
-				return $negativeRange;
+				return $this->resolveType(new Node\Expr\BinaryOp\Mul($node->expr, new LNumber(-1)));
 			}
 
 			return $type;
@@ -5221,6 +5216,13 @@ private function integerRangeMath(Type $range, Expr $node, Type $operand): Type
 				[$min, $max] = [$max, $min];
 			}
 
+			// invert maximas on multiplication with negative constants
+			if ((($range instanceof ConstantIntegerType && $range->getValue() < 0)
+				|| ($operand instanceof ConstantIntegerType && $operand->getValue() < 0))
+				&& ($min === null || $max === null)) {
+				[$min, $max] = [$max, $min];
+			}
+
 		} else {
 			if ($operand instanceof ConstantIntegerType) {
 				$min = $rangeMin !== null && $operand->getValue() !== 0 ? $rangeMin / $operand->getValue() : null;
@@ -5246,6 +5248,13 @@ private function integerRangeMath(Type $range, Expr $node, Type $operand): Type
 					[$min, $max] = [$max, $min];
 				}
 
+				// invert maximas on division with negative constants
+				if ((($range instanceof ConstantIntegerType && $range->getValue() < 0)
+						|| ($operand instanceof ConstantIntegerType && $operand->getValue() < 0))
+					&& ($min === null || $max === null)) {
+					[$min, $max] = [$max, $min];
+				}
+
 				if ($min === null && $max === null) {
 					return new BenevolentUnionType([new IntegerType(), new FloatType()]);
 				}

tests/PHPStan/Analyser/data/integer-range-types.php

@@ -232,8 +232,8 @@ public function math($i, $j, $z, $pi, $r1, $r2, $rMin, $rMax, $x, $y) {
 		assertType('int<-2, 9>|int<21, 30>', $r1 - $z);
 		assertType('int<-200, -20>|int<1, 30>', $r1 * $z);
 		assertType('float|int<0, 10>', $r1 / $z);
-		assertType('int<min, 15>', $rMin * $z);
-		assertType('int<-100, max>', $rMax * $z);
+		assertType('int', $rMin * $z);
+		assertType('int<min, -100>|int<5, max>', $rMax * $z);
 
 		assertType('int<2, max>', $pi + 1);
 		assertType('int<-1, max>', $pi - 2);
@@ -277,6 +277,28 @@ public function math($i, $j, $z, $pi, $r1, $r2, $rMin, $rMax, $x, $y) {
 		assertType('float|int<5, max>', $rMax / $r1);
 
 		assertType('5|10|15|20|30', $x / $y);
+
+	}
+
+	/**
+	 * @param int<min, 5> $rMin
+	 * @param int<5, max> $rMax
+	 *
+	 * @see https://www.wolframalpha.com/input/?i=%28interval%5B2%2C%E2%88%9E%5D+%2F+-1%29
+	 * @see https://3v4l.org/ur9Wf
+	 */
+	public function maximaInversion($rMin, $rMax) {
+		assertType('int<-5, max>', -1 * $rMin);
+		assertType('int<min, -10>', -2 * $rMax);
+
+		assertType('int<-5, max>', $rMin * -1);
+		assertType('int<min, -10>', $rMax * -2);
+
+		assertType('float|int<0, max>', -1 / $rMin);
+		assertType('float|int<min, 0>', -2 / $rMax);
+
+		assertType('float|int<-5, max>', $rMin / -1);
+		assertType('float|int<min, -2>', $rMax / -2);
 	}
 
 	/**