diff --git a/phpstan-baseline.neon b/phpstan-baseline.neon
index d252aaef59..495bdbefb7 100644
--- a/phpstan-baseline.neon
+++ b/phpstan-baseline.neon
@@ -411,30 +411,12 @@ parameters:
 			count: 1
 			path: src/Reflection/SignatureMap/Php8SignatureMapProvider.php
 
-		-
-			message: '#^Doing instanceof PHPStan\\Type\\Constant\\ConstantStringType is error\-prone and deprecated\. Use Type\:\:getConstantStrings\(\) instead\.$#'
-			identifier: phpstanApi.instanceofType
-			count: 1
-			path: src/Rules/Api/NodeConnectingVisitorAttributesRule.php
-
-		-
-			message: '#^Doing instanceof PHPStan\\Type\\ConstantScalarType is error\-prone and deprecated\. Use Type\:\:isConstantScalarValue\(\) or Type\:\:getConstantScalarTypes\(\) or Type\:\:getConstantScalarValues\(\) instead\.$#'
-			identifier: phpstanApi.instanceofType
-			count: 1
-			path: src/Rules/Arrays/DuplicateKeysInLiteralArraysRule.php
-
 		-
 			message: '#^Doing instanceof PHPStan\\Type\\Constant\\ConstantBooleanType is error\-prone and deprecated\. Use Type\:\:isTrue\(\) or Type\:\:isFalse\(\) instead\.$#'
 			identifier: phpstanApi.instanceofType
 			count: 2
 			path: src/Rules/Classes/ImpossibleInstanceOfRule.php
 
-		-
-			message: '#^Doing instanceof PHPStan\\Type\\ObjectType is error\-prone and deprecated\. Use Type\:\:isObject\(\) or Type\:\:getObjectClassNames\(\) instead\.$#'
-			identifier: phpstanApi.instanceofType
-			count: 2
-			path: src/Rules/Classes/RequireExtendsRule.php
-
 		-
 			message: '#^Doing instanceof PHPStan\\Type\\ObjectType is error\-prone and deprecated\. Use Type\:\:isObject\(\) or Type\:\:getObjectClassNames\(\) instead\.$#'
 			identifier: phpstanApi.instanceofType
@@ -459,12 +441,6 @@ parameters:
 			count: 6
 			path: src/Rules/Comparison/BooleanOrConstantConditionRule.php
 
-		-
-			message: '#^Doing instanceof PHPStan\\Type\\Constant\\ConstantBooleanType is error\-prone and deprecated\. Use Type\:\:isTrue\(\) or Type\:\:isFalse\(\) instead\.$#'
-			identifier: phpstanApi.instanceofType
-			count: 2
-			path: src/Rules/Comparison/ConstantLooseComparisonRule.php
-
 		-
 			message: '#^Doing instanceof PHPStan\\Type\\Constant\\ConstantBooleanType is error\-prone and deprecated\. Use Type\:\:isTrue\(\) or Type\:\:isFalse\(\) instead\.$#'
 			identifier: phpstanApi.instanceofType
@@ -492,7 +468,7 @@ parameters:
 		-
 			message: '#^Doing instanceof PHPStan\\Type\\Constant\\ConstantBooleanType is error\-prone and deprecated\. Use Type\:\:isTrue\(\) or Type\:\:isFalse\(\) instead\.$#'
 			identifier: phpstanApi.instanceofType
-			count: 2
+			count: 1
 			path: src/Rules/Comparison/ImpossibleCheckTypeHelper.php
 
 		-
@@ -645,18 +621,6 @@ parameters:
 			count: 1
 			path: src/Rules/Methods/StaticMethodCallCheck.php
 
-		-
-			message: '#^Doing instanceof PHPStan\\Type\\ObjectType is error\-prone and deprecated\. Use Type\:\:isObject\(\) or Type\:\:getObjectClassNames\(\) instead\.$#'
-			identifier: phpstanApi.instanceofType
-			count: 1
-			path: src/Rules/PhpDoc/RequireExtendsCheck.php
-
-		-
-			message: '#^Doing instanceof PHPStan\\Type\\ObjectType is error\-prone and deprecated\. Use Type\:\:isObject\(\) or Type\:\:getObjectClassNames\(\) instead\.$#'
-			identifier: phpstanApi.instanceofType
-			count: 1
-			path: src/Rules/PhpDoc/RequireImplementsDefinitionTraitRule.php
-
 		-
 			message: '#^Doing instanceof PHPStan\\Type\\Generic\\GenericObjectType is error\-prone and deprecated\.$#'
 			identifier: phpstanApi.instanceofType
@@ -675,36 +639,6 @@ parameters:
 			count: 1
 			path: src/Rules/RuleLevelHelper.php
 
-		-
-			message: '#^Doing instanceof PHPStan\\Type\\ObjectType is error\-prone and deprecated\. Use Type\:\:isObject\(\) or Type\:\:getObjectClassNames\(\) instead\.$#'
-			identifier: phpstanApi.instanceofType
-			count: 2
-			path: src/Rules/RuleLevelHelper.php
-
-		-
-			message: '#^Doing instanceof PHPStan\\Type\\Constant\\ConstantBooleanType is error\-prone and deprecated\. Use Type\:\:isTrue\(\) or Type\:\:isFalse\(\) instead\.$#'
-			identifier: phpstanApi.instanceofType
-			count: 1
-			path: src/Rules/TooWideTypehints/TooWideMethodReturnTypehintRule.php
-
-		-
-			message: '#^Doing instanceof PHPStan\\Type\\Constant\\ConstantStringType is error\-prone and deprecated\. Use Type\:\:getConstantStrings\(\) instead\.$#'
-			identifier: phpstanApi.instanceofType
-			count: 1
-			path: src/Rules/UnusedFunctionParametersCheck.php
-
-		-
-			message: '#^Doing instanceof PHPStan\\Type\\Constant\\ConstantArrayType is error\-prone and deprecated\. Use Type\:\:getConstantArrays\(\) instead\.$#'
-			identifier: phpstanApi.instanceofType
-			count: 1
-			path: src/Rules/Variables/CompactVariablesRule.php
-
-		-
-			message: '#^Doing instanceof PHPStan\\Type\\Constant\\ConstantStringType is error\-prone and deprecated\. Use Type\:\:getConstantStrings\(\) instead\.$#'
-			identifier: phpstanApi.instanceofType
-			count: 1
-			path: src/Rules/Variables/CompactVariablesRule.php
-
 		-
 			message: '''
 				#^Call to deprecated method assertFileNotExists\(\) of class PHPUnit\\Framework\\Assert\:
diff --git a/src/Rules/Api/NodeConnectingVisitorAttributesRule.php b/src/Rules/Api/NodeConnectingVisitorAttributesRule.php
index 7ad74631b9..282c2189d2 100644
--- a/src/Rules/Api/NodeConnectingVisitorAttributesRule.php
+++ b/src/Rules/Api/NodeConnectingVisitorAttributesRule.php
@@ -7,7 +7,6 @@
 use PHPStan\Analyser\Scope;
 use PHPStan\Rules\Rule;
 use PHPStan\Rules\RuleErrorBuilder;
-use PHPStan\Type\Constant\ConstantStringType;
 use PHPStan\Type\ObjectType;
 use function array_keys;
 use function in_array;
@@ -41,37 +40,40 @@ public function processNode(Node $node, Scope $scope): array
 		if (!isset($args[0])) {
 			return [];
 		}
+
+		$messages = [];
 		$argType = $scope->getType($args[0]->value);
-		if (!$argType instanceof ConstantStringType) {
-			return [];
-		}
-		if (!in_array($argType->getValue(), ['parent', 'previous', 'next'], true)) {
-			return [];
-		}
-		if (!$scope->isInClass()) {
-			return [];
-		}
+		foreach ($argType->getConstantStrings() as $constantString) {
+			$argValue = $constantString->getValue();
+			if (!in_array($argValue, ['parent', 'previous', 'next'], true)) {
+				continue;
+			}
 
-		$classReflection = $scope->getClassReflection();
-		$hasPhpStanInterface = false;
-		foreach (array_keys($classReflection->getInterfaces()) as $interfaceName) {
-			if (!str_starts_with($interfaceName, 'PHPStan\\')) {
+			if (!$scope->isInClass()) {
 				continue;
 			}
 
-			$hasPhpStanInterface = true;
-		}
+			$classReflection = $scope->getClassReflection();
+			$hasPhpStanInterface = false;
+			foreach (array_keys($classReflection->getInterfaces()) as $interfaceName) {
+				if (!str_starts_with($interfaceName, 'PHPStan\\')) {
+					continue;
+				}
 
-		if (!$hasPhpStanInterface) {
-			return [];
-		}
+				$hasPhpStanInterface = true;
+			}
 
-		return [
-			RuleErrorBuilder::message(sprintf('Node attribute \'%s\' is no longer available.', $argType->getValue()))
+			if (!$hasPhpStanInterface) {
+				continue;
+			}
+
+			$messages[] = RuleErrorBuilder::message(sprintf('Node attribute \'%s\' is no longer available.', $argValue))
 				->identifier('phpParser.nodeConnectingAttribute')
 				->tip('See: https://phpstan.org/blog/preprocessing-ast-for-custom-rules')
-				->build(),
-		];
+				->build();
+		}
+
+		return $messages;
 	}
 
 }
diff --git a/src/Rules/Arrays/DuplicateKeysInLiteralArraysRule.php b/src/Rules/Arrays/DuplicateKeysInLiteralArraysRule.php
index 46b5e712e1..7e54a2cb15 100644
--- a/src/Rules/Arrays/DuplicateKeysInLiteralArraysRule.php
+++ b/src/Rules/Arrays/DuplicateKeysInLiteralArraysRule.php
@@ -9,10 +9,10 @@
 use PHPStan\Rules\Rule;
 use PHPStan\Rules\RuleErrorBuilder;
 use PHPStan\Type\Constant\ConstantIntegerType;
-use PHPStan\Type\ConstantScalarType;
 use function array_keys;
 use function count;
 use function implode;
+use function is_int;
 use function max;
 use function sprintf;
 use function var_export;
@@ -70,38 +70,38 @@ public function processNode(Node $node, Scope $scope): array
 				}
 			} else {
 				$keyType = $itemNode->getScope()->getType($key);
-
-				$arrayKeyValue = $keyType->toArrayKey();
-				if ($arrayKeyValue instanceof ConstantIntegerType) {
+				$arrayKeyValues = $keyType->toArrayKey()->getConstantScalarValues();
+				if (count($arrayKeyValues) === 1 && is_int($arrayKeyValues[0])) {
 					$autoGeneratedIndex = $autoGeneratedIndex === null
-						? $arrayKeyValue->getValue()
-						: max($autoGeneratedIndex, $arrayKeyValue->getValue());
+						? $arrayKeyValues[0]
+						: max($autoGeneratedIndex, $arrayKeyValues[0]);
 				}
 			}
 
-			if (!$keyType instanceof ConstantScalarType) {
+			$keyValues = $keyType->getConstantScalarValues();
+			if (count($keyValues) === 0) {
 				$autoGeneratedIndex = false;
 				continue;
 			}
 
-			$value = $keyType->getValue();
-			$printedValue = $key !== null
-				? $this->exprPrinter->printExpr($key)
-				: $value;
+			foreach ($keyValues as $value) {
+				$printedValue = $key !== null
+					? $this->exprPrinter->printExpr($key)
+					: $value;
+				$printedValues[$value][] = $printedValue;
 
-			$printedValues[$value][] = $printedValue;
+				if (!isset($valueLines[$value])) {
+					$valueLines[$value] = $item->getStartLine();
+				}
 
-			if (!isset($valueLines[$value])) {
-				$valueLines[$value] = $item->getStartLine();
-			}
+				$previousCount = count($values);
+				$values[$value] = $printedValue;
+				if ($previousCount !== count($values)) {
+					continue;
+				}
 
-			$previousCount = count($values);
-			$values[$value] = $printedValue;
-			if ($previousCount !== count($values)) {
-				continue;
+				$duplicateKeys[$value] = true;
 			}
-
-			$duplicateKeys[$value] = true;
 		}
 
 		$messages = [];
diff --git a/src/Rules/Classes/RequireExtendsRule.php b/src/Rules/Classes/RequireExtendsRule.php
index 036cf3aa85..88c0b88ccd 100644
--- a/src/Rules/Classes/RequireExtendsRule.php
+++ b/src/Rules/Classes/RequireExtendsRule.php
@@ -7,7 +7,6 @@
 use PHPStan\Node\InClassNode;
 use PHPStan\Rules\Rule;
 use PHPStan\Rules\RuleErrorBuilder;
-use PHPStan\Type\ObjectType;
 use PHPStan\Type\VerbosityLevel;
 use function sprintf;
 
@@ -35,24 +34,24 @@ public function processNode(Node $node, Scope $scope): array
 			$extendsTags = $interface->getRequireExtendsTags();
 			foreach ($extendsTags as $extendsTag) {
 				$type = $extendsTag->getType();
-				if (!$type instanceof ObjectType) {
-					continue;
-				}
+				foreach ($type->getObjectClassNames() as $className) {
+					if ($classReflection->is($className)) {
+						continue;
+					}
 
-				if ($classReflection->is($type->getClassName())) {
-					continue;
-				}
+					$errors[] = RuleErrorBuilder::message(
+						sprintf(
+							'Interface %s requires implementing class to extend %s, but %s does not.',
+							$interface->getDisplayName(),
+							$type->describe(VerbosityLevel::typeOnly()),
+							$classReflection->getDisplayName(),
+						),
+					)
+						->identifier('class.missingExtends')
+						->build();
 
-				$errors[] = RuleErrorBuilder::message(
-					sprintf(
-						'Interface %s requires implementing class to extend %s, but %s does not.',
-						$interface->getDisplayName(),
-						$type->describe(VerbosityLevel::typeOnly()),
-						$classReflection->getDisplayName(),
-					),
-				)
-					->identifier('class.missingExtends')
-					->build();
+					break;
+				}
 			}
 		}
 
@@ -60,24 +59,24 @@ public function processNode(Node $node, Scope $scope): array
 			$extendsTags = $trait->getRequireExtendsTags();
 			foreach ($extendsTags as $extendsTag) {
 				$type = $extendsTag->getType();
-				if (!$type instanceof ObjectType) {
-					continue;
-				}
+				foreach ($type->getObjectClassNames() as $className) {
+					if ($classReflection->is($className)) {
+						continue;
+					}
 
-				if ($classReflection->is($type->getClassName())) {
-					continue;
-				}
+					$errors[] = RuleErrorBuilder::message(
+						sprintf(
+							'Trait %s requires using class to extend %s, but %s does not.',
+							$trait->getDisplayName(),
+							$type->describe(VerbosityLevel::typeOnly()),
+							$classReflection->getDisplayName(),
+						),
+					)
+						->identifier('class.missingExtends')
+						->build();
 
-				$errors[] = RuleErrorBuilder::message(
-					sprintf(
-						'Trait %s requires using class to extend %s, but %s does not.',
-						$trait->getDisplayName(),
-						$type->describe(VerbosityLevel::typeOnly()),
-						$classReflection->getDisplayName(),
-					),
-				)
-					->identifier('class.missingExtends')
-					->build();
+					break;
+				}
 			}
 		}
 
diff --git a/src/Rules/Comparison/ConstantLooseComparisonRule.php b/src/Rules/Comparison/ConstantLooseComparisonRule.php
index 09961335e7..b7d3fe977d 100644
--- a/src/Rules/Comparison/ConstantLooseComparisonRule.php
+++ b/src/Rules/Comparison/ConstantLooseComparisonRule.php
@@ -7,7 +7,6 @@
 use PHPStan\Parser\LastConditionVisitor;
 use PHPStan\Rules\Rule;
 use PHPStan\Rules\RuleErrorBuilder;
-use PHPStan\Type\Constant\ConstantBooleanType;
 use PHPStan\Type\VerbosityLevel;
 use function sprintf;
 
@@ -37,7 +36,7 @@ public function processNode(Node $node, Scope $scope): array
 		}
 
 		$nodeType = $this->treatPhpDocTypesAsCertain ? $scope->getType($node) : $scope->getNativeType($node);
-		if (!$nodeType instanceof ConstantBooleanType) {
+		if (!$nodeType->isTrue()->yes() && !$nodeType->isFalse()->yes()) {
 			return [];
 		}
 
@@ -47,7 +46,7 @@ public function processNode(Node $node, Scope $scope): array
 			}
 
 			$instanceofTypeWithoutPhpDocs = $scope->getNativeType($node);
-			if ($instanceofTypeWithoutPhpDocs instanceof ConstantBooleanType) {
+			if ($instanceofTypeWithoutPhpDocs->isTrue()->yes() || $instanceofTypeWithoutPhpDocs->isFalse()->yes()) {
 				return $ruleErrorBuilder;
 			}
 			if (!$this->treatPhpDocTypesAsCertainTip) {
@@ -57,7 +56,7 @@ public function processNode(Node $node, Scope $scope): array
 			return $ruleErrorBuilder->treatPhpDocTypesAsCertainTip();
 		};
 
-		if (!$nodeType->getValue()) {
+		if ($nodeType->isFalse()->yes()) {
 			return [
 				$addTip(RuleErrorBuilder::message(sprintf(
 					'Loose comparison using %s between %s and %s will always evaluate to false.',
diff --git a/src/Rules/Comparison/ImpossibleCheckTypeHelper.php b/src/Rules/Comparison/ImpossibleCheckTypeHelper.php
index 48eea97d6f..6cbe4b1b59 100644
--- a/src/Rules/Comparison/ImpossibleCheckTypeHelper.php
+++ b/src/Rules/Comparison/ImpossibleCheckTypeHelper.php
@@ -69,11 +69,12 @@ public function findSpecifiedType(
 				if ($functionName === 'assert' && $argsCount >= 1) {
 					$arg = $node->getArgs()[0]->value;
 					$assertValue = ($this->treatPhpDocTypesAsCertain ? $scope->getType($arg) : $scope->getNativeType($arg))->toBoolean();
-					if (!$assertValue instanceof ConstantBooleanType) {
+					if (! $assertValue->isTrue()->yes() && ! $assertValue->isFalse()->yes()) {
 						return null;
 					}
 
-					return $assertValue->getValue();
+					/** @var bool */
+					return $assertValue->getConstantScalarValues()[0];
 				}
 				if (in_array($functionName, [
 					'class_exists',
diff --git a/src/Rules/PhpDoc/RequireExtendsCheck.php b/src/Rules/PhpDoc/RequireExtendsCheck.php
index 14f6d43647..7decad9c63 100644
--- a/src/Rules/PhpDoc/RequireExtendsCheck.php
+++ b/src/Rules/PhpDoc/RequireExtendsCheck.php
@@ -8,10 +8,12 @@
 use PHPStan\Rules\ClassNameNodePair;
 use PHPStan\Rules\IdentifierRuleError;
 use PHPStan\Rules\RuleErrorBuilder;
-use PHPStan\Type\ObjectType;
 use PHPStan\Type\VerbosityLevel;
+use function array_column;
+use function array_map;
 use function array_merge;
 use function count;
+use function sort;
 use function sprintf;
 use function strtolower;
 
@@ -41,39 +43,48 @@ public function checkExtendsTags(Node $node, array $extendsTags): array
 
 		foreach ($extendsTags as $extendsTag) {
 			$type = $extendsTag->getType();
-			if (!$type instanceof ObjectType) {
+			$classNames = $type->getObjectClassNames();
+			if (count($classNames) === 0) {
 				$errors[] = RuleErrorBuilder::message(sprintf('PHPDoc tag @phpstan-require-extends contains non-object type %s.', $type->describe(VerbosityLevel::typeOnly())))
 					->identifier('requireExtends.nonObject')
 					->build();
 				continue;
 			}
 
-			$class = $type->getClassName();
-			$referencedClassReflection = $type->getClassReflection();
+			sort($classNames);
+			$referencedClassReflections = array_map(static fn ($reflection) => [$reflection, $reflection->getName()], $type->getObjectClassReflections());
+			$referencedClassReflectionsMap = array_column($referencedClassReflections, 0, 1);
+			foreach ($classNames as $class) {
+				$referencedClassReflection = $referencedClassReflectionsMap[$class] ?? null;
+				if ($referencedClassReflection === null) {
+					$errors[] = RuleErrorBuilder::message(sprintf('PHPDoc tag @phpstan-require-extends contains unknown class %s.', $class))
+						->discoveringSymbolsTip()
+						->identifier('class.notFound')
+						->build();
+					continue;
+				}
 
-			if ($referencedClassReflection === null) {
-				$errors[] = RuleErrorBuilder::message(sprintf('PHPDoc tag @phpstan-require-extends contains unknown class %s.', $class))
-					->discoveringSymbolsTip()
-					->identifier('class.notFound')
-					->build();
-				continue;
-			}
-
-			if (!$referencedClassReflection->isClass()) {
-				$errors[] = RuleErrorBuilder::message(sprintf('PHPDoc tag @phpstan-require-extends cannot contain non-class type %s.', $class))
-					->identifier(sprintf('requireExtends.%s', strtolower($referencedClassReflection->getClassTypeDescription())))
-					->build();
-			} elseif ($referencedClassReflection->isFinal()) {
-				$errors[] = RuleErrorBuilder::message(sprintf('PHPDoc tag @phpstan-require-extends cannot contain final class %s.', $class))
-					->identifier('requireExtends.finalClass')
-					->build();
-			} else {
-				$errors = array_merge(
-					$errors,
-					$this->classCheck->checkClassNames([
-						new ClassNameNodePair($class, $node),
-					], $this->checkClassCaseSensitivity),
-				);
+				if ($referencedClassReflection->isInterface()) {
+					$errors[] = RuleErrorBuilder::message(sprintf('PHPDoc tag @phpstan-require-extends cannot contain an interface %s, expected a class.', $class))
+						->tip('If you meant an interface, use @phpstan-require-implements instead.')
+						->identifier('requireExtends.interface')
+						->build();
+				} elseif (!$referencedClassReflection->isClass()) {
+					$errors[] = RuleErrorBuilder::message(sprintf('PHPDoc tag @phpstan-require-extends cannot contain non-class type %s.', $class))
+						->identifier(sprintf('requireExtends.%s', strtolower($referencedClassReflection->getClassTypeDescription())))
+						->build();
+				} elseif ($referencedClassReflection->isFinal()) {
+					$errors[] = RuleErrorBuilder::message(sprintf('PHPDoc tag @phpstan-require-extends cannot contain final class %s.', $class))
+						->identifier('requireExtends.finalClass')
+						->build();
+				} else {
+					$errors = array_merge(
+						$errors,
+						$this->classCheck->checkClassNames([
+							new ClassNameNodePair($class, $node),
+						], $this->checkClassCaseSensitivity),
+					);
+				}
 			}
 		}
 
diff --git a/src/Rules/PhpDoc/RequireImplementsDefinitionTraitRule.php b/src/Rules/PhpDoc/RequireImplementsDefinitionTraitRule.php
index 076ae342a0..e974a7c055 100644
--- a/src/Rules/PhpDoc/RequireImplementsDefinitionTraitRule.php
+++ b/src/Rules/PhpDoc/RequireImplementsDefinitionTraitRule.php
@@ -9,9 +9,11 @@
 use PHPStan\Rules\ClassNameNodePair;
 use PHPStan\Rules\Rule;
 use PHPStan\Rules\RuleErrorBuilder;
-use PHPStan\Type\ObjectType;
 use PHPStan\Type\VerbosityLevel;
+use function array_column;
+use function array_map;
 use function array_merge;
+use function count;
 use function sprintf;
 use function strtolower;
 
@@ -49,34 +51,39 @@ public function processNode(Node $node, Scope $scope): array
 		$errors = [];
 		foreach ($implementsTags as $implementsTag) {
 			$type = $implementsTag->getType();
-			if (!$type instanceof ObjectType) {
+			$classNames = $type->getObjectClassNames();
+			if (count($classNames) === 0) {
 				$errors[] = RuleErrorBuilder::message(sprintf('PHPDoc tag @phpstan-require-implements contains non-object type %s.', $type->describe(VerbosityLevel::typeOnly())))
 					->identifier('requireImplements.nonObject')
 					->build();
 				continue;
 			}
 
-			$class = $type->getClassName();
-			$referencedClassReflection = $type->getClassReflection();
-			if ($referencedClassReflection === null) {
-				$errors[] = RuleErrorBuilder::message(sprintf('PHPDoc tag @phpstan-require-implements contains unknown class %s.', $class))
-					->discoveringSymbolsTip()
-					->identifier('class.notFound')
-					->build();
-				continue;
-			}
+			$referencedClassReflections = array_map(static fn ($reflection) => [$reflection, $reflection->getName()], $type->getObjectClassReflections());
+			$referencedClassReflectionsMap = array_column($referencedClassReflections, 0, 1);
+			foreach ($classNames as $class) {
+				$referencedClassReflection = $referencedClassReflectionsMap[$class] ?? null;
+				if ($referencedClassReflection === null) {
+					$errors[] = RuleErrorBuilder::message(sprintf('PHPDoc tag @phpstan-require-implements contains unknown class %s.', $class))
+						->discoveringSymbolsTip()
+						->identifier('class.notFound')
+						->build();
+					continue;
+				}
+
+				if (!$referencedClassReflection->isInterface()) {
+					$errors[] = RuleErrorBuilder::message(sprintf('PHPDoc tag @phpstan-require-implements cannot contain non-interface type %s.', $class))
+						->identifier(sprintf('requireImplements.%s', strtolower($referencedClassReflection->getClassTypeDescription())))
+						->build();
+				} else {
+					$errors = array_merge(
+						$errors,
+						$this->classCheck->checkClassNames([
+							new ClassNameNodePair($class, $node),
+						], $this->checkClassCaseSensitivity),
+					);
+				}
 
-			if (!$referencedClassReflection->isInterface()) {
-				$errors[] = RuleErrorBuilder::message(sprintf('PHPDoc tag @phpstan-require-implements cannot contain non-interface type %s.', $class))
-					->identifier(sprintf('requireImplements.%s', strtolower($referencedClassReflection->getClassTypeDescription())))
-					->build();
-			} else {
-				$errors = array_merge(
-					$errors,
-					$this->classCheck->checkClassNames([
-						new ClassNameNodePair($class, $node),
-					], $this->checkClassCaseSensitivity),
-				);
 			}
 		}
 
diff --git a/src/Rules/RuleLevelHelper.php b/src/Rules/RuleLevelHelper.php
index 416583546f..eb025ac4e2 100644
--- a/src/Rules/RuleLevelHelper.php
+++ b/src/Rules/RuleLevelHelper.php
@@ -14,7 +14,6 @@
 use PHPStan\Type\MixedType;
 use PHPStan\Type\NeverType;
 use PHPStan\Type\NullType;
-use PHPStan\Type\ObjectType;
 use PHPStan\Type\StrictMixedType;
 use PHPStan\Type\Type;
 use PHPStan\Type\TypeCombinator;
@@ -304,10 +303,9 @@ private function findTypeToCheckImplementation(
 		if (
 			$type instanceof UnionType
 			&& count($type->getTypes()) === 2
-			&& $type->getTypes()[0] instanceof ObjectType
-			&& $type->getTypes()[1] instanceof ObjectType
-			&& $type->getTypes()[0]->getClassName() === 'PhpParser\\Node\\Arg'
-			&& $type->getTypes()[1]->getClassName() === 'PhpParser\\Node\\VariadicPlaceholder'
+			&& $type->isObject()->yes()
+			&& $type->getTypes()[0]->getObjectClassNames() === ['PhpParser\\Node\\Arg']
+			&& $type->getTypes()[1]->getObjectClassNames() === ['PhpParser\\Node\\VariadicPlaceholder']
 			&& !$unionTypeCriteriaCallback($type)
 		) {
 			$tip = 'Use <fg=cyan>->getArgs()</> instead of <fg=cyan>->args</>.';
diff --git a/src/Rules/TooWideTypehints/TooWideMethodReturnTypehintRule.php b/src/Rules/TooWideTypehints/TooWideMethodReturnTypehintRule.php
index 1c40c4a9ce..8737855175 100644
--- a/src/Rules/TooWideTypehints/TooWideMethodReturnTypehintRule.php
+++ b/src/Rules/TooWideTypehints/TooWideMethodReturnTypehintRule.php
@@ -7,7 +7,6 @@
 use PHPStan\Node\MethodReturnStatementsNode;
 use PHPStan\Rules\Rule;
 use PHPStan\Rules\RuleErrorBuilder;
-use PHPStan\Type\Constant\ConstantBooleanType;
 use PHPStan\Type\TypeCombinator;
 use PHPStan\Type\TypeUtils;
 use PHPStan\Type\UnionType;
@@ -82,9 +81,9 @@ public function processNode(Node $node, Scope $scope): array
 
 		$returnType = TypeCombinator::union(...$returnTypes);
 		if (
-			!$method->isPrivate()
-			&& ($returnType->isNull()->yes() || $returnType instanceof ConstantBooleanType)
-			&& !$isFirstDeclaration
+			!$isFirstDeclaration
+			&& !$method->isPrivate()
+			&& ($returnType->isNull()->yes() || $returnType->isTrue()->yes() || $returnType->isFalse()->yes())
 		) {
 			return [];
 		}
diff --git a/src/Rules/UnusedFunctionParametersCheck.php b/src/Rules/UnusedFunctionParametersCheck.php
index 628041a032..68c1549091 100644
--- a/src/Rules/UnusedFunctionParametersCheck.php
+++ b/src/Rules/UnusedFunctionParametersCheck.php
@@ -7,7 +7,6 @@
 use PHPStan\Analyser\Scope;
 use PHPStan\Reflection\ReflectionProvider;
 use PHPStan\ShouldNotHappenException;
-use PHPStan\Type\Constant\ConstantStringType;
 use function array_combine;
 use function array_map;
 use function array_merge;
@@ -92,11 +91,9 @@ private function getUsedVariables(Scope $scope, $node): array
 			) {
 				foreach ($node->getArgs() as $arg) {
 					$argType = $scope->getType($arg->value);
-					if (!($argType instanceof ConstantStringType)) {
-						continue;
+					foreach ($argType->getConstantStrings() as $constantStringType) {
+						$variableNames[] = $constantStringType->getValue();
 					}
-
-					$variableNames[] = $argType->getValue();
 				}
 			}
 			foreach ($node->getSubNodeNames() as $subNodeName) {
diff --git a/src/Rules/Variables/CompactVariablesRule.php b/src/Rules/Variables/CompactVariablesRule.php
index c6324f7678..8555675bd3 100644
--- a/src/Rules/Variables/CompactVariablesRule.php
+++ b/src/Rules/Variables/CompactVariablesRule.php
@@ -6,10 +6,10 @@
 use PHPStan\Analyser\Scope;
 use PHPStan\Rules\Rule;
 use PHPStan\Rules\RuleErrorBuilder;
-use PHPStan\Type\Constant\ConstantArrayType;
 use PHPStan\Type\Constant\ConstantStringType;
 use PHPStan\Type\Type;
 use function array_merge;
+use function count;
 use function sprintf;
 use function strtolower;
 
@@ -66,25 +66,24 @@ public function processNode(Node $node, Scope $scope): array
 	}
 
 	/**
-	 * @return array<int, ConstantStringType>
+	 * @return list<ConstantStringType>
 	 */
 	private function findConstantStrings(Type $type): array
 	{
-		if ($type instanceof ConstantStringType) {
-			return [$type];
+		$constantStrings = $type->getConstantStrings();
+		if (count($constantStrings) > 0) {
+			return $constantStrings;
 		}
 
-		if ($type instanceof ConstantArrayType) {
-			$result = [];
-			foreach ($type->getValueTypes() as $valueType) {
+		$result = [];
+		foreach ($type->getConstantArrays() as $constantArrayType) {
+			foreach ($constantArrayType->getValueTypes() as $valueType) {
 				$constantStrings = $this->findConstantStrings($valueType);
 				$result = array_merge($result, $constantStrings);
 			}
-
-			return $result;
 		}
 
-		return [];
+		return $result;
 	}
 
 }
diff --git a/tests/PHPStan/Rules/Api/NodeConnectingVisitorAttributesRuleTest.php b/tests/PHPStan/Rules/Api/NodeConnectingVisitorAttributesRuleTest.php
index c7fe99bc18..b811039ec7 100644
--- a/tests/PHPStan/Rules/Api/NodeConnectingVisitorAttributesRuleTest.php
+++ b/tests/PHPStan/Rules/Api/NodeConnectingVisitorAttributesRuleTest.php
@@ -21,7 +21,12 @@ public function testRule(): void
 		$this->analyse([__DIR__ . '/data/node-connecting-visitor.php'], [
 			[
 				'Node attribute \'parent\' is no longer available.',
-				18,
+				22,
+				'See: https://phpstan.org/blog/preprocessing-ast-for-custom-rules',
+			],
+			[
+				'Node attribute \'parent\' is no longer available.',
+				24,
 				'See: https://phpstan.org/blog/preprocessing-ast-for-custom-rules',
 			],
 		]);
diff --git a/tests/PHPStan/Rules/Api/data/node-connecting-visitor.php b/tests/PHPStan/Rules/Api/data/node-connecting-visitor.php
index e61c7c3a4d..93f18f28a9 100644
--- a/tests/PHPStan/Rules/Api/data/node-connecting-visitor.php
+++ b/tests/PHPStan/Rules/Api/data/node-connecting-visitor.php
@@ -8,6 +8,10 @@
 
 class MyRule implements Rule
 {
+
+	/** @var 'parent'|'myCustomAttribute' */
+	public string $attrName;
+
 	public function getNodeType(): string
 	{
 		return Node::class;
@@ -17,6 +21,7 @@ public function processNode(Node $node, Scope $scope): array
 	{
 		$parent = $node->getAttribute("parent");
 		$custom = $node->getAttribute("myCustomAttribute");
+		$parent = $node->getAttribute($this->attrName);
 
 		return [];
 	}
diff --git a/tests/PHPStan/Rules/Arrays/DuplicateKeysInLiteralArraysRuleTest.php b/tests/PHPStan/Rules/Arrays/DuplicateKeysInLiteralArraysRuleTest.php
index 87b5a12e5f..6d775a2f7c 100644
--- a/tests/PHPStan/Rules/Arrays/DuplicateKeysInLiteralArraysRuleTest.php
+++ b/tests/PHPStan/Rules/Arrays/DuplicateKeysInLiteralArraysRuleTest.php
@@ -61,6 +61,18 @@ public function testDuplicateKeys(): void
 				'Array has 2 duplicate keys with value -41 (-41, -41).',
 				76,
 			],
+			[
+				'Array has 2 duplicate keys with value \'foo\' (\'foo\', $key).',
+				102,
+			],
+			[
+				'Array has 2 duplicate keys with value \'bar\' (\'bar\', $key).',
+				103,
+			],
+			[
+				'Array has 2 duplicate keys with value \'key\' (\'key\', $key2).',
+				105,
+			],
 		]);
 	}
 
diff --git a/tests/PHPStan/Rules/Arrays/data/duplicate-keys.php b/tests/PHPStan/Rules/Arrays/data/duplicate-keys.php
index 02176773ac..06dbbeb0f5 100644
--- a/tests/PHPStan/Rules/Arrays/data/duplicate-keys.php
+++ b/tests/PHPStan/Rules/Arrays/data/duplicate-keys.php
@@ -92,4 +92,19 @@ public function doWithoutKeys(int $int)
 		];
 	}
 
+	/**
+	 * @param 'foo'|'bar' $key
+	 */
+	public function doUnionKeys(string $key): void
+	{
+		$key2 = 'key';
+		$a = [
+			'foo' => 'foo',
+			'bar' => 'bar',
+			$key => 'foo|bar',
+			'key' => 'bar',
+			$key2 => 'foo',
+		];
+	}
+
 }
diff --git a/tests/PHPStan/Rules/Classes/RequireExtendsRuleTest.php b/tests/PHPStan/Rules/Classes/RequireExtendsRuleTest.php
index 0ca40d9fa4..03f3361bef 100644
--- a/tests/PHPStan/Rules/Classes/RequireExtendsRuleTest.php
+++ b/tests/PHPStan/Rules/Classes/RequireExtendsRuleTest.php
@@ -52,6 +52,22 @@ public function testRule(): void
 				'Trait IncompatibleRequireExtends\ValidPsalmTrait requires using class to extend IncompatibleRequireExtends\SomeClass, but class@anonymous/tests/PHPStan/Rules/PhpDoc/data/incompatible-require-extends.php:163 does not.',
 				163,
 			],
+			[
+				'Interface IncompatibleRequireExtends\RequireNonExisstentUnionClassinterface requires implementing class to extend IncompatibleRequireExtends\NonExistentClass|IncompatibleRequireExtends\SomeClass, but IncompatibleRequireExtends\RequireNonExisstentUnionClassinterface@anonymous/tests/PHPStan/Rules/PhpDoc/data/incompatible-require-extends.php:185 does not.',
+				185,
+			],
+			[
+				'Interface IncompatibleRequireExtends\RequireNonExisstentUnionClassinterface requires implementing class to extend IncompatibleRequireExtends\NonExistentClass|IncompatibleRequireExtends\SomeClass, but IncompatibleRequireExtends\SomeClass@anonymous/tests/PHPStan/Rules/PhpDoc/data/incompatible-require-extends.php:187 does not.',
+				187,
+			],
+			[
+				'Trait IncompatibleRequireExtends\RequireNonExisstentUnionClassTrait requires using class to extend IncompatibleRequireExtends\NonExistentClass|IncompatibleRequireExtends\SomeClass, but class@anonymous/tests/PHPStan/Rules/PhpDoc/data/incompatible-require-extends.php:194 does not.',
+				194,
+			],
+			[
+				'Trait IncompatibleRequireExtends\RequireNonExisstentUnionClassTrait requires using class to extend IncompatibleRequireExtends\NonExistentClass|IncompatibleRequireExtends\SomeClass, but IncompatibleRequireExtends\SomeClass@anonymous/tests/PHPStan/Rules/PhpDoc/data/incompatible-require-extends.php:198 does not.',
+				198,
+			],
 		];
 
 		$this->analyse([__DIR__ . '/../PhpDoc/data/incompatible-require-extends.php'], $expectedErrors);
diff --git a/tests/PHPStan/Rules/PhpDoc/RequireExtendsDefinitionClassRuleTest.php b/tests/PHPStan/Rules/PhpDoc/RequireExtendsDefinitionClassRuleTest.php
index 5a24e75502..6a40619bea 100644
--- a/tests/PHPStan/Rules/PhpDoc/RequireExtendsDefinitionClassRuleTest.php
+++ b/tests/PHPStan/Rules/PhpDoc/RequireExtendsDefinitionClassRuleTest.php
@@ -45,8 +45,9 @@ public function testRule(): void
 				8,
 			],
 			[
-				'PHPDoc tag @phpstan-require-extends cannot contain non-class type IncompatibleRequireExtends\SomeInterface.',
+				'PHPDoc tag @phpstan-require-extends cannot contain an interface IncompatibleRequireExtends\SomeInterface, expected a class.',
 				13,
+				'If you meant an interface, use @phpstan-require-implements instead.',
 			],
 			[
 				$enumError,
@@ -75,13 +76,24 @@ public function testRule(): void
 				121,
 			],
 			[
-				'PHPDoc tag @phpstan-require-extends contains non-object type IncompatibleRequireExtends\UnresolvableExtendsInterface&stdClass.',
+				'PHPDoc tag @phpstan-require-extends cannot contain an interface IncompatibleRequireExtends\UnresolvableExtendsInterface, expected a class.',
 				135,
+				'If you meant an interface, use @phpstan-require-implements instead.',
 			],
 			[
 				'PHPDoc tag @phpstan-require-extends can only be used once.',
 				178,
 			],
+			[
+				'PHPDoc tag @phpstan-require-extends contains unknown class IncompatibleRequireExtends\NonExistentClass.',
+				183,
+				'Learn more at https://phpstan.org/user-guide/discovering-symbols',
+			],
+			[
+				'PHPDoc tag @phpstan-require-extends contains unknown class IncompatibleRequireExtends\SomeClass.',
+				183,
+				'Learn more at https://phpstan.org/user-guide/discovering-symbols',
+			],
 		]);
 	}
 
diff --git a/tests/PHPStan/Rules/PhpDoc/RequireExtendsDefinitionTraitRuleTest.php b/tests/PHPStan/Rules/PhpDoc/RequireExtendsDefinitionTraitRuleTest.php
index 746c3b9007..121fc0df34 100644
--- a/tests/PHPStan/Rules/PhpDoc/RequireExtendsDefinitionTraitRuleTest.php
+++ b/tests/PHPStan/Rules/PhpDoc/RequireExtendsDefinitionTraitRuleTest.php
@@ -45,6 +45,16 @@ public function testRule(): void
 				'PHPDoc tag @phpstan-require-extends can only be used once.',
 				171,
 			],
+			[
+				'PHPDoc tag @phpstan-require-extends contains unknown class IncompatibleRequireExtends\NonExistentClass.',
+				192,
+				'Learn more at https://phpstan.org/user-guide/discovering-symbols',
+			],
+			[
+				'PHPDoc tag @phpstan-require-extends contains unknown class IncompatibleRequireExtends\SomeClass.',
+				192,
+				'Learn more at https://phpstan.org/user-guide/discovering-symbols',
+			],
 		]);
 	}
 
diff --git a/tests/PHPStan/Rules/PhpDoc/data/incompatible-require-extends.php b/tests/PHPStan/Rules/PhpDoc/data/incompatible-require-extends.php
index eb362e5b61..6b5af9e340 100644
--- a/tests/PHPStan/Rules/PhpDoc/data/incompatible-require-extends.php
+++ b/tests/PHPStan/Rules/PhpDoc/data/incompatible-require-extends.php
@@ -176,3 +176,25 @@ trait TooMuchExtends {}
  * @phpstan-require-extends SomeOtherClass
  */
 interface TooMuchExtendsIface {}
+
+/**
+ * @phpstan-require-extends SomeClass|NonExistentClass
+ */
+interface RequireNonExisstentUnionClassinterface {}
+
+new class implements RequireNonExisstentUnionClassinterface {};
+
+new class extends SomeClass implements RequireNonExisstentUnionClassinterface {};
+
+/**
+ * @phpstan-require-extends SomeClass|NonExistentClass
+ */
+trait RequireNonExisstentUnionClassTrait {}
+
+new class {
+	use RequireNonExisstentUnionClassTrait;
+};
+
+new class extends SomeClass {
+	use RequireNonExisstentUnionClassTrait;
+};