Fix supertype checks between int range and constant int union

src/Type/IntegerRangeType.php

@@ -5,8 +5,10 @@
 use PHPStan\TrinaryLogic;
 use PHPStan\Type\Constant\ConstantBooleanType;
 use PHPStan\Type\Constant\ConstantIntegerType;
+use function array_filter;
 use function assert;
 use function ceil;
+use function count;
 use function floor;
 use function get_class;
 use function is_int;
@@ -244,13 +246,33 @@ public function isSubTypeOf(Type $otherType): TrinaryLogic
 			return $otherType->isSuperTypeOf($this);
 		}
 
-		if ($otherType instanceof UnionType || $otherType instanceof IntersectionType) {
+		if ($otherType instanceof UnionType) {
+			return $this->isSubTypeOfUnion($otherType);
+		}
+
+		if ($otherType instanceof IntersectionType) {
 			return $otherType->isSuperTypeOf($this);
 		}
 
 		return TrinaryLogic::createNo();
 	}
 
+	private function isSubTypeOfUnion(UnionType $otherType): TrinaryLogic
+	{
+		if ($this->min !== null && $this->max !== null) {
+			$matchingConstantIntegers = array_filter(
+				$otherType->getTypes(),
+				fn (Type $type): bool => $type instanceof ConstantIntegerType && $type->getValue() >= $this->min && $type->getValue() <= $this->max,
+			);
+
+			if (count($matchingConstantIntegers) === ($this->max - $this->min + 1)) {
+				return TrinaryLogic::createYes();
+			}
+		}
+
+		return TrinaryLogic::createNo()->lazyOr($otherType->getTypes(), fn (Type $innerType) => $this->isSubTypeOf($innerType));
+	}
+
 	public function isAcceptedBy(Type $acceptingType, bool $strictTypes): TrinaryLogic
 	{
 		return $this->isSubTypeOf($acceptingType);

src/Type/UnionType.php

@@ -133,6 +133,7 @@ public function isSuperTypeOf(Type $otherType): TrinaryLogic
 			|| $otherType instanceof NeverType
 			|| $otherType instanceof ConditionalType
 			|| $otherType instanceof ConditionalTypeForParameter
+			|| $otherType instanceof IntegerRangeType
 		) {
 			return $otherType->isSubTypeOf($this);
 		}

tests/PHPStan/Rules/Properties/TypesAssignedToPropertiesRuleTest.php

@@ -445,4 +445,10 @@ public function testBug4680(): void
 		$this->analyse([__DIR__ . '/data/bug-4680.php'], []);
 	}
 
+	public function testBug3383(): void
+	{
+		$this->checkExplicitMixed = true;
+		$this->analyse([__DIR__ . '/data/bug-3383.php'], []);
+	}
+
 }

tests/PHPStan/Rules/Properties/data/bug-3383.php

@@ -0,0 +1,13 @@
+<?php declare(strict_types = 1);
+
+namespace Bug3383;
+
+class HelloWorld
+{
+	/** @var 0|1|2|3 */
+	public $classification = 0;
+
+	public function test(): void {
+		$this->classification = random_int(0, 3);
+	}
+}