Fix MixedType->equals(ErrorType)

src/Type/MixedType.php

@@ -37,6 +37,7 @@
 use PHPStan\Type\Traits\NonGeneralizableTypeTrait;
 use PHPStan\Type\Traits\NonGenericTypeTrait;
 use PHPStan\Type\Traits\UndecidedComparisonCompoundTypeTrait;
+use function get_class;
 use function sprintf;
 
 /** @api */
@@ -310,7 +311,7 @@ public function getCallableParametersAcceptors(ClassMemberAccessAnswerer $scope)
 
 	public function equals(Type $type): bool
 	{
-		if (!$type instanceof self) {
+		if (get_class($type) !== static::class) {
 			return false;
 		}
 

tests/PHPStan/Generics/TemplateTypeFactoryTest.php

@@ -55,7 +55,12 @@ public function dataCreate(): array
 					null,
 					TemplateTypeVariance::createInvariant(),
 				),
-				new MixedType(),
+				TemplateTypeFactory::create(
+					TemplateTypeScope::createWithFunction('a'),
+					'U',
+					null,
+					TemplateTypeVariance::createInvariant(),
+				),
 			],
 			[
 				new UnionType([

tests/PHPStan/Type/MixedTypeTest.php

@@ -1164,4 +1164,50 @@ public function testSubtractedHasOffsetValueType(MixedType $mixedType, Type $typ
 		);
 	}
 
+	/** @dataProvider dataEquals */
+	public function testEquals(MixedType $mixedType, Type $typeToCompare, bool $expectedResult): void
+	{
+		$this->assertSame(
+			$expectedResult,
+			$mixedType->equals($typeToCompare),
+			sprintf('%s -> equals(%s)', $mixedType->describe(VerbosityLevel::precise()), $typeToCompare->describe(VerbosityLevel::precise())),
+		);
+	}
+
+	public function dataEquals(): array
+	{
+		return [
+			[
+				new MixedType(),
+				new MixedType(),
+				true,
+			],
+			[
+				new MixedType(true),
+				new MixedType(),
+				true,
+			],
+			[
+				new MixedType(),
+				new MixedType(true),
+				true,
+			],
+			[
+				new MixedType(),
+				new MixedType(true, new IntegerType()),
+				false,
+			],
+			[
+				new MixedType(),
+				new ErrorType(),
+				false,
+			],
+			[
+				new MixedType(true),
+				new ErrorType(),
+				false,
+			],
+		];
+	}
+
 }