diff --git a/lib/Doctrine/ORM/Configuration.php b/lib/Doctrine/ORM/Configuration.php
index a7676f35220..0236b196259 100644
--- a/lib/Doctrine/ORM/Configuration.php
+++ b/lib/Doctrine/ORM/Configuration.php
@@ -442,6 +442,7 @@ public function addCustomStringFunction($name, $className)
      * @param string $name
      *
      * @return string|null
+     * @psalm-return ?class-string
      */
     public function getCustomStringFunction($name)
     {
@@ -494,6 +495,7 @@ public function addCustomNumericFunction($name, $className)
      * @param string $name
      *
      * @return string|null
+     * @psalm-return ?class-string
      */
     public function getCustomNumericFunction($name)
     {
@@ -534,6 +536,8 @@ public function setCustomNumericFunctions(array $functions)
      * @param string|callable $className Class name or a callable that returns the function.
      *
      * @return void
+     *
+     * @psalm-param class-string|callable $className
      */
     public function addCustomDatetimeFunction($name, $className)
     {
@@ -546,6 +550,8 @@ public function addCustomDatetimeFunction($name, $className)
      * @param string $name
      *
      * @return string|null
+     *
+     * @psalm-return ?class-string $name
      */
     public function getCustomDatetimeFunction($name)
     {
@@ -567,6 +573,8 @@ public function getCustomDatetimeFunction($name)
      * @param array $functions The map of custom DQL date/time functions.
      *
      * @return void
+     *
+     * @psalm-param array<string, string> $functions
      */
     public function setCustomDatetimeFunctions(array $functions)
     {
@@ -597,6 +605,8 @@ public function setCustomHydrationModes($modes)
      * @param string $modeName The hydration mode name.
      *
      * @return string|null The hydrator class name.
+     *
+     * @psalm-return ?class-string
      */
     public function getCustomHydrationMode($modeName)
     {
@@ -624,6 +634,8 @@ public function addCustomHydrationMode($modeName, $hydrator)
      * @param string $cmfName
      *
      * @return void
+     *
+     * @psalm-param class-string $cmfName
      */
     public function setClassMetadataFactoryName($cmfName)
     {
@@ -632,6 +644,8 @@ public function setClassMetadataFactoryName($cmfName)
 
     /**
      * @return string
+     *
+     * @psalm-return class-string
      */
     public function getClassMetadataFactoryName()
     {
@@ -658,8 +672,10 @@ public function addFilter($name, $className)
      *
      * @param string $name The name of the filter.
      *
-     * @return string The class name of the filter, or null if it is not
+     * @return string|null The class name of the filter, or null if it is not
      *  defined.
+     *
+     * @psalm-return ?class-string
      */
     public function getFilterClassName($name)
     {
@@ -696,6 +712,8 @@ public function setDefaultRepositoryClassName($className)
      * @since 2.2
      *
      * @return string
+     *
+     * @psalm-return class-string
      */
     public function getDefaultRepositoryClassName()
     {
diff --git a/lib/Doctrine/ORM/Mapping/ClassMetadataInfo.php b/lib/Doctrine/ORM/Mapping/ClassMetadataInfo.php
index 94987d5fb84..b78e2d980c4 100644
--- a/lib/Doctrine/ORM/Mapping/ClassMetadataInfo.php
+++ b/lib/Doctrine/ORM/Mapping/ClassMetadataInfo.php
@@ -252,7 +252,8 @@ class ClassMetadataInfo implements ClassMetadata
      * The name of the custom repository class used for the entity class.
      * (Optional).
      *
-     * @var string
+     * @var string|null
+     * @psalm-var ?class-string
      */
     public $customRepositoryClassName;
 
@@ -2626,6 +2627,8 @@ protected function _storeAssociationMapping(array $assocMapping)
      * @param string $repositoryClassName The class name of the custom mapper.
      *
      * @return void
+     *
+     * @psalm-param class-string $repositoryClassName
      */
     public function setCustomRepositoryClass($repositoryClassName)
     {
@@ -3254,6 +3257,8 @@ public function getAssociationsByTargetClass($targetClass)
      * @param  string|null $className
      *
      * @return string|null null if the input value is null
+     *
+     * @psalm-param ?class-string $className
      */
     public function fullyQualifiedClassName($className)
     {
diff --git a/lib/Doctrine/ORM/Mapping/DefaultEntityListenerResolver.php b/lib/Doctrine/ORM/Mapping/DefaultEntityListenerResolver.php
index a8ee2dc783d..ee3e37a32a8 100644
--- a/lib/Doctrine/ORM/Mapping/DefaultEntityListenerResolver.php
+++ b/lib/Doctrine/ORM/Mapping/DefaultEntityListenerResolver.php
@@ -30,6 +30,8 @@ class DefaultEntityListenerResolver implements EntityListenerResolver
 {
     /**
      * @var array Map to store entity listener instances.
+     *
+     * @psalm-var array<class-string, object>
      */
     private $instances = [];
 
diff --git a/lib/Doctrine/ORM/Mapping/EntityListenerResolver.php b/lib/Doctrine/ORM/Mapping/EntityListenerResolver.php
index b0c62c8c3a3..d3a41af994f 100644
--- a/lib/Doctrine/ORM/Mapping/EntityListenerResolver.php
+++ b/lib/Doctrine/ORM/Mapping/EntityListenerResolver.php
@@ -34,6 +34,8 @@ interface EntityListenerResolver
      * @param string $className The fully-qualified class name
      *
      * @return void
+     *
+     * @psalm-param class-string $className
      */
     function clear($className = null);
 
@@ -43,6 +45,8 @@ function clear($className = null);
      * @param string $className The fully-qualified class name
      *
      * @return object An entity listener
+     *
+     * @psalm-param class-string $className
      */
     function resolve($className);
 
diff --git a/lib/Doctrine/ORM/Query/FilterCollection.php b/lib/Doctrine/ORM/Query/FilterCollection.php
index ca7f1ac3289..c5f627e8396 100644
--- a/lib/Doctrine/ORM/Query/FilterCollection.php
+++ b/lib/Doctrine/ORM/Query/FilterCollection.php
@@ -20,6 +20,7 @@
 namespace Doctrine\ORM\Query;
 
 use Doctrine\ORM\EntityManagerInterface;
+use function assert;
 
 /**
  * Collection class for all the query filters.
@@ -110,6 +111,8 @@ public function enable($name)
         if ( ! $this->isEnabled($name)) {
             $filterClass = $this->config->getFilterClassName($name);
 
+            assert($filterClass !== null);
+
             $this->enabledFilters[$name] = new $filterClass($this->em);
 
             // Keep the enabled filters sorted for the hash
diff --git a/lib/Doctrine/ORM/Query/Parser.php b/lib/Doctrine/ORM/Query/Parser.php
index d0170792604..c3de92a124d 100644
--- a/lib/Doctrine/ORM/Query/Parser.php
+++ b/lib/Doctrine/ORM/Query/Parser.php
@@ -42,6 +42,8 @@ class Parser
      * READ-ONLY: Maps BUILT-IN string function names to AST class names.
      *
      * @var array
+     *
+     * @psalm-var class-string<Functions\FunctionNode>
      */
     private static $_STRING_FUNCTIONS = [
         'concat'    => Functions\ConcatFunction::class,
@@ -56,6 +58,8 @@ class Parser
      * READ-ONLY: Maps BUILT-IN numeric function names to AST class names.
      *
      * @var array
+     *
+     * @psalm-var class-string<Functions\FunctionNode>
      */
     private static $_NUMERIC_FUNCTIONS = [
         'length'    => Functions\LengthFunction::class,
@@ -80,6 +84,8 @@ class Parser
      * READ-ONLY: Maps BUILT-IN datetime function names to AST class names.
      *
      * @var array
+     *
+     * @psalm-var class-string<Functions\FunctionNode>
      */
     private static $_DATETIME_FUNCTIONS = [
         'current_date'      => Functions\CurrentDateFunction::class,
diff --git a/lib/Doctrine/ORM/Query/SqlWalker.php b/lib/Doctrine/ORM/Query/SqlWalker.php
index 0749fb715dd..b25df759103 100644
--- a/lib/Doctrine/ORM/Query/SqlWalker.php
+++ b/lib/Doctrine/ORM/Query/SqlWalker.php
@@ -142,6 +142,8 @@ class SqlWalker implements TreeWalker
      * Map of all components/classes that appear in the DQL query.
      *
      * @var array
+     *
+     * @psalm-var array<string, array{metadata: ClassMetadata}>
      */
     private $queryComponents;
 
@@ -199,7 +201,7 @@ public function __construct($query, $parserResult, array $queryComponents)
     /**
      * Gets the Query instance used by the walker.
      *
-     * @return Query.
+     * @return Query
      */
     public function getQuery()
     {
@@ -232,6 +234,8 @@ public function getEntityManager()
      * @param string $dqlAlias The DQL alias.
      *
      * @return array
+     *
+     * @psalm-return array{metadata: ClassMetadata}
      */
     public function getQueryComponent($dqlAlias)
     {
@@ -1522,7 +1526,7 @@ public function walkSimpleSelectClause($simpleSelectClause)
     /**
      * @param \Doctrine\ORM\Query\AST\ParenthesisExpression $parenthesisExpression
      *
-     * @return string.
+     * @return string
      */
     public function walkParenthesisExpression(AST\ParenthesisExpression $parenthesisExpression)
     {
diff --git a/lib/Doctrine/ORM/Tools/Console/MetadataFilter.php b/lib/Doctrine/ORM/Tools/Console/MetadataFilter.php
index 88357e35c94..f0c5669a31e 100644
--- a/lib/Doctrine/ORM/Tools/Console/MetadataFilter.php
+++ b/lib/Doctrine/ORM/Tools/Console/MetadataFilter.php
@@ -19,6 +19,8 @@
 
 namespace Doctrine\ORM\Tools\Console;
 
+use Doctrine\Common\Persistence\Mapping\ClassMetadata;
+
 /**
  * Used by CLI Tools to restrict entity-based commands to given patterns.
  *
@@ -40,10 +42,10 @@ class MetadataFilter extends \FilterIterator implements \Countable
     /**
      * Filter Metadatas by one or more filter options.
      *
-     * @param array        $metadatas
-     * @param array|string $filter
+     * @param ClassMetadata[] $metadatas
+     * @param string[]|string $filter
      *
-     * @return array
+     * @return ClassMetadata[]
      */
     static public function filter(array $metadatas, $filter)
     {
diff --git a/lib/Doctrine/ORM/Tools/EntityGenerator.php b/lib/Doctrine/ORM/Tools/EntityGenerator.php
index be8d87803b0..fcc9d6fc25f 100644
--- a/lib/Doctrine/ORM/Tools/EntityGenerator.php
+++ b/lib/Doctrine/ORM/Tools/EntityGenerator.php
@@ -149,7 +149,7 @@ class EntityGenerator
     /**
      * Whether or not to make generated embeddables immutable.
      *
-     * @var boolean.
+     * @var bool
      */
     protected $embeddablesImmutable = false;
 
diff --git a/lib/Doctrine/ORM/UnitOfWork.php b/lib/Doctrine/ORM/UnitOfWork.php
index 77b42cca287..3383a44b0c9 100644
--- a/lib/Doctrine/ORM/UnitOfWork.php
+++ b/lib/Doctrine/ORM/UnitOfWork.php
@@ -1893,7 +1893,7 @@ public function merge($entity)
      * @param object      $entity
      * @param array       $visited
      * @param object|null $prevManagedCopy
-     * @param array|null  $assoc
+     * @param string[]    $assoc
      *
      * @return object The managed copy of the entity.
      *