Cannot create IntersectionType with less than two types

Author: ondrejmirtes

src/Type/IntersectionType.php

@@ -33,6 +33,16 @@ class IntersectionType implements CompoundType
 	 */
 	public function __construct(array $types)
 	{
+		if (count($types) < 2) {
+			throw new \PHPStan\ShouldNotHappenException(sprintf(
+				'Cannot create %s with: %s',
+				self::class,
+				implode(', ', array_map(static function (Type $type): string {
+					return $type->describe(VerbosityLevel::value());
+				}, $types))
+			));
+		}
+
 		$this->types = UnionTypeHelper::sortTypes($types);
 	}
 

tests/PHPStan/Type/CallableTypeTest.php

@@ -5,6 +5,7 @@
 use PHPStan\Reflection\Native\NativeParameterReflection;
 use PHPStan\Reflection\PassedByReference;
 use PHPStan\TrinaryLogic;
+use PHPStan\Type\Accessory\AccessoryNonEmptyStringType;
 use PHPStan\Type\Accessory\HasMethodType;
 use PHPStan\Type\Constant\ConstantArrayType;
 use PHPStan\Type\Constant\ConstantIntegerType;
@@ -99,17 +100,12 @@ public function dataIsSubTypeOf(): array
 			],
 			[
 				new CallableType(),
-				new IntersectionType([new CallableType()]),
-				TrinaryLogic::createYes(),
-			],
-			[
-				new CallableType(),
-				new IntersectionType([new StringType()]),
+				new IntersectionType([new StringType(), new AccessoryNonEmptyStringType()]),
 				TrinaryLogic::createMaybe(),
 			],
 			[
 				new CallableType(),
-				new IntersectionType([new IntegerType()]),
+				new IntegerType(),
 				TrinaryLogic::createNo(),
 			],
 			[

tests/PHPStan/Type/IntersectionTypeTest.php

@@ -147,16 +147,6 @@ public function dataIsSuperTypeOf(): \Iterator
 			TrinaryLogic::createNo(),
 		];
 
-		$intersectionTypeB = new IntersectionType([
-			new IntegerType(),
-		]);
-
-		yield [
-			$intersectionTypeB,
-			$intersectionTypeB,
-			TrinaryLogic::createYes(),
-		];
-
 		yield [
 			new IntersectionType([
 				new ArrayType(new MixedType(), new MixedType()),
@@ -335,16 +325,6 @@ public function dataIsSubTypeOf(): \Iterator
 			TrinaryLogic::createNo(),
 		];
 
-		$intersectionTypeB = new IntersectionType([
-			new IntegerType(),
-		]);
-
-		yield [
-			$intersectionTypeB,
-			$intersectionTypeB,
-			TrinaryLogic::createYes(),
-		];
-
 		$intersectionTypeC = new IntersectionType([
 			new StringType(),
 			new CallableType(),

tests/PHPStan/Type/TypeCombinatorTest.php

@@ -1825,7 +1825,7 @@ public function dataUnion(): array
 			[
 				[
 					new UnionType([
-						new IntersectionType([new ArrayType(new MixedType(), new MixedType())]),
+						new ArrayType(new MixedType(), new MixedType()),
 						IntegerRangeType::fromInterval(null, -1),
 						IntegerRangeType::fromInterval(1, null),
 					]),
@@ -1842,7 +1842,7 @@ public function dataUnion(): array
 			[
 				[
 					new UnionType([
-						new IntersectionType([new ArrayType(new MixedType(), new MixedType())]),
+						new ArrayType(new MixedType(), new MixedType()),
 						new CallableType(),
 					]),
 					TemplateTypeFactory::create(