diff --git a/phpstan.neon b/phpstan.neon
index 7656bd8..b899433 100644
--- a/phpstan.neon
+++ b/phpstan.neon
@@ -9,4 +9,46 @@ parameters:
 	stubFiles:
 	ignoreErrors:
 		- identifier: missingType.generics
-		- '#Interface must be located in "Contract" or "Contracts" namespace#'
\ No newline at end of file
+		- '#Interface must be located in "Contract" or "Contracts" namespace#'
+		- '#Dynamic call to static method Kalnoy\\Nestedset\\QueryBuilder<.*>::select\(\).#'
+		- '#Dynamic call to static method Kalnoy\\Nestedset\\QueryBuilder<.*>::from\(\).#'
+		- '#Dynamic call to static method Kalnoy\\Nestedset\\QueryBuilder<.*>::whereRaw\(\).#'
+		- '#Dynamic call to static method Kalnoy\\Nestedset\\QueryBuilder<.*>::whereNested\(\).#'
+		# bunch of false positives from Eloquent
+		# ---------------------------------------------------------------------------------------- 
+		- '#Parameter .* \$models .* of method .*::initRelation\(\) should be contravariant with parameter \$models .* of method .*::initRelation\(\)#'
+		- '#Parameter .* \$models .* of method .*::addEagerConstraints\(\) should be contravariant with parameter \$models .* of method .*::addEagerConstraints\(\)#'
+		- '#Parameter .* \$models .* of method .*::match\(\) should be contravariant with parameter \$models .* of method .*::match\(\)#'
+
+		# - '#Method .*::ancestorsOf\(\) should return Illuminate\\Database\\Eloquent\\Collection<.*, .* Illuminate\\Database\\Eloquent\\Model> but returns Illuminate\\Database\\Eloquent\\Collection<int, Illuminate\\Database\\Eloquent\\Model>.#'
+		# - '#Method .*::ancestorsAndSelf\(\) should return Illuminate\\Database\\Eloquent\\Collection<.*, .* Illuminate\\Database\\Eloquent\\Model> but returns Illuminate\\Database\\Eloquent\\Collection<int, Illuminate\\Database\\Eloquent\\Model>.#'
+		# - '#Method .*::descendantsOf\(\) should return Illuminate\\Database\\Eloquent\\Collection<.*, .* Illuminate\\Database\\Eloquent\\Model> but returns Illuminate\\Database\\Eloquent\\Collection<int, Illuminate\\Database\\Eloquent\\Model>.#'
+		# - '#Method .*::descendantsAndSelf\(\) should return Illuminate\\Database\\Eloquent\\Collection<.*, .* Illuminate\\Database\\Eloquent\\Model> but returns Illuminate\\Database\\Eloquent\\Collection<int, Illuminate\\Database\\Eloquent\\Model>.#'
+		# - '#Parameter #1 $query of method Kalnoy\Nestedset\BaseRelation<Tmodel of                    
+        #  Illuminate\Database\Eloquent\Model&Kalnoy\Nestedset\Node>::addEagerConstraint() expects  
+        #  Kalnoy\Nestedset\QueryBuilder, Illuminate\Database\Eloquent\Builder given.#'
+		# - '#Parameter \#1 \$model \(Illuminate\\Database\\Eloquent\\Model&Kalnoy\\Nestedset\\Node\) of method Kalnoy\\Nestedset\\AncestorsRelation::matches\(\) should be contravariant with parameter \$model \(Illuminate\\Database\\Eloquent\\Model\) of method Kalnoy\\Nestedset\\BaseRelation::matches\(\)#'
+		# - '#Parameter \#2 \$related \(Kalnoy\\Nestedset\\Node\) of method Kalnoy\\Nestedset\\AncestorsRelation::matches\(\) should be contravariant with parameter \$related \(mixed\) of method Kalnoy\\Nestedset\\BaseRelation::matches\(\)#'
+		# - '#Parameter \#1 \$models \(array<int, Tmodel>\) of method Kalnoy\\Nestedset\\BaseRelation::initRelation\(\) should be contravariant with parameter \$models \(array\) of method Illuminate\\Database\\Eloquent\\Relations\\Relation<Illuminate\\Database\\Eloquent\\Model>::initRelation\(\)#'
+		# - '#Dynamic call to static method (Illuminate\\Database\\Query\\Builder|Illuminate\\Database\\Eloquent\\(Builder|Relations\\.*))(<.*>)?::from\(\).#'
+		# - '#Dynamic call to static method (Illuminate\\Database\\Query\\Builder|Illuminate\\Database\\Eloquent\\(Builder|Relations\\.*))(<.*>)?::limit\(\).#'
+		# - '#Dynamic call to static method (Illuminate\\Database\\Query\\Builder|Illuminate\\Database\\Eloquent\\(Builder|Relations\\.*))(<.*>)?::offset\(\).#'
+		# - '#Dynamic call to static method (Illuminate\\Database\\Query\\Builder|Illuminate\\Database\\Eloquent\\(Builder|Relations\\.*))(<.*>)?::take\(\).#'
+		# - '#Dynamic call to static method (Illuminate\\Database\\Query\\Builder|Illuminate\\Database\\Eloquent\\(Builder|Relations\\.*))(<.*>)?::truncate\(\).#'
+		# - '#Dynamic call to static method (Illuminate\\Database\\Query\\Builder|Illuminate\\Database\\Eloquent\\(Builder|Relations\\.*))(<.*>)?::insert\(\).#'
+		# - '#Dynamic call to static method (Illuminate\\Database\\Query\\Builder|Illuminate\\Database\\Eloquent\\(Builder|Relations\\.*))(<.*>)?::select\(\).#'
+		# - '#Dynamic call to static method (Illuminate\\Database\\Query\\Builder|Illuminate\\Database\\Eloquent\\(Builder|Relations\\.*))(<.*>)?::orderBy\(\)#'
+		# - '#Dynamic call to static method (Illuminate\\Database\\Query\\Builder|Illuminate\\Database\\Eloquent\\(Builder|Relations\\.*))(<.*>)?::where(Not)?(Null|In|Between|Exists|Column|Year|Month|Day)?\(\).#'
+		# - '#Dynamic call to static method (Illuminate\\Database\\Query\\Builder|Illuminate\\Database\\Eloquent\\(Builder|Relations\\.*))(<.*>)?::delete\(\)#'
+		# - '#Dynamic call to static method (Illuminate\\Database\\Query\\Builder|Illuminate\\Database\\Eloquent\\(Builder|Relations\\.*))(<.*>)?::without\(\)#'
+		# - '#Dynamic call to static method (Illuminate\\Database\\Query\\Builder|Illuminate\\Database\\Eloquent\\(Builder|Relations\\.*))(<.*>)?::with\(\)#'
+		# - '#Dynamic call to static method (Illuminate\\Database\\Query\\Builder|Illuminate\\Database\\Eloquent\\(Builder|Relations\\.*))(<.*>)?::count\(\).#'
+		# - '#Dynamic call to static method (Illuminate\\Database\\Query\\Builder|Illuminate\\Database\\Eloquent\\(Builder|Relations\\.*))(<.*>)?::update\(\).#'
+		# - '#Dynamic call to static method (Illuminate\\Database\\Query\\Builder|Illuminate\\Database\\Eloquent\\(Builder|Relations\\.*))(<.*>)?::inRandomOrder\(\).#'
+		# - '#Dynamic call to static method (Illuminate\\Database\\Query\\Builder|Illuminate\\Database\\Eloquent\\(Builder|Relations\\.*))(<.*>)?::groupBy\(\).#'
+		# - '#Dynamic call to static method (Illuminate\\Database\\Query\\Builder|Illuminate\\Database\\Eloquent\\(Builder|Relations\\.*))(<.*>)?::latest\(\).#'
+		# - '#Dynamic call to static method (Illuminate\\Database\\Query\\Builder|Illuminate\\Database\\Eloquent\\(Builder|Relations\\.*))(<.*>)?::first\(\).#'
+		# - '#Dynamic call to static method (Illuminate\\Database\\Query\\Builder|Illuminate\\Database\\Eloquent\\(Builder|Relations\\.*))(<.*>)?::skip\(\).#'
+		# - '#Call to an undefined method Illuminate\\Database\\Eloquent\\.*::with(Only)?\(\)#'
+		# - '#Call to an undefined method Illuminate\\Database\\Eloquent\\Builder|Illuminate\\Database\\Eloquent\\Relations\\Relation::whereNotNull\(\).#'
+		# - '#Call to protected method asDateTime\(\) of class Illuminate\\Database\\Eloquent\\Model.#'
\ No newline at end of file
diff --git a/src/AncestorsRelation.php b/src/AncestorsRelation.php
index 68dbeaf..f5d212b 100644
--- a/src/AncestorsRelation.php
+++ b/src/AncestorsRelation.php
@@ -5,7 +5,7 @@
 use Illuminate\Database\Eloquent\Model;
 
 /**
- * @template T
+ * @disregard P1037
  */
 class AncestorsRelation extends BaseRelation
 {
@@ -25,12 +25,12 @@ public function addConstraints()
 	}
 
 	/**
-	 * @param Model $model
-	 * @param       $related
+	 * @param Model&Node $model
+	 * @param Node $related
 	 *
 	 * @return bool
 	 */
-	protected function matches(Model $model, $related)
+	protected function matches(Model $model, $related): bool
 	{
 		return $related->isAncestorOf($model);
 	}
diff --git a/src/BaseRelation.php b/src/BaseRelation.php
index 141a44f..ff77a8c 100644
--- a/src/BaseRelation.php
+++ b/src/BaseRelation.php
@@ -8,6 +8,14 @@
 use Illuminate\Database\Eloquent\Relations\Relation;
 use Illuminate\Database\Query\Builder;
 
+/**
+ * @template Tmodelkey
+ * @template Tmodel of Model&Node<Tmodelkey,Model>
+ * @extends Relation<Tmodel>
+ * @property Tmodel $related
+ * @property Tmodel $parent
+ * @method Tmodel getParent()
+ */
 abstract class BaseRelation extends Relation
 {
 	/**
@@ -43,12 +51,12 @@ public function __construct(QueryBuilder $builder, Model $model)
 	}
 
 	/**
-	 * @param Model $model
-	 * @param       $related
+	 * @param Model&Node $model
+	 * @param Node $related
 	 *
 	 * @return bool
 	 */
-	abstract protected function matches(Model $model, $related);
+	abstract protected function matches(Model&Node $model, Node $related): bool;
 
 	/**
 	 * @param QueryBuilder $query
@@ -71,14 +79,14 @@ abstract protected function relationExistenceCondition(string $hash, string $tab
 	/**
 	 * @param EloquentBuilder $query
 	 * @param EloquentBuilder $parent
-	 * @param string[]        $columns
+	 * @param mixed           $columns
 	 *
-	 * @return mixed
+	 * @return EloquentBuilder
 	 */
 	public function getRelationExistenceQuery(EloquentBuilder $query, EloquentBuilder $parent,
 		$columns = ['*']
 	) {
-		$query = $this->getParent()->replicate()->newScopedQuery()->select($columns);
+		$query = $this->getParent()->replicate()->newScopedQuery()->select($columns); 
 
 		$table = $query->getModel()->getTable();
 
@@ -100,10 +108,10 @@ public function getRelationExistenceQuery(EloquentBuilder $query, EloquentBuilde
 	/**
 	 * Initialize the relation on a set of models.
 	 *
-	 * @param array  $models
+	 * @param array<int,Tmodel>  $models
 	 * @param string $relation
 	 *
-	 * @return array
+	 * @return array<int,Tmodel>
 	 */
 	public function initRelation(array $models, $relation)
 	{
@@ -135,7 +143,7 @@ public function getResults()
 	/**
 	 * Set the constraints for an eager load of the relation.
 	 *
-	 * @param array $models
+	 * @param array<int,Tmodel> $models
 	 *
 	 * @return void
 	 */
@@ -160,11 +168,11 @@ public function addEagerConstraints(array $models)
 	/**
 	 * Match the eagerly loaded results to their parents.
 	 *
-	 * @param array              $models
+	 * @param array<int,Tmodel>              $models
 	 * @param EloquentCollection $results
 	 * @param string             $relation
 	 *
-	 * @return array
+	 * @return array<int,Tmodel>
 	 */
 	public function match(array $models, EloquentCollection $results, $relation)
 	{
@@ -178,15 +186,17 @@ public function match(array $models, EloquentCollection $results, $relation)
 	}
 
 	/**
-	 * @param Model              $model
+	 * @param Tmodel             $model
 	 * @param EloquentCollection $results
 	 *
 	 * @return Collection
 	 */
 	protected function matchForModel(Model $model, EloquentCollection $results)
 	{
+		/** @var Collection<int,Tmodel> */
 		$result = $this->related->newCollection();
 
+		/** @var Tmodel $related */
 		foreach ($results as $related) {
 			if ($this->matches($model, $related)) {
 				$result->push($related);
diff --git a/src/Collection.php b/src/Collection.php
index cfc563f..e38664b 100644
--- a/src/Collection.php
+++ b/src/Collection.php
@@ -2,10 +2,16 @@
 
 namespace Kalnoy\Nestedset;
 
-use Illuminate\Database\Eloquent\Collection as BaseCollection;
+use Illuminate\Database\Eloquent\Collection as EloquentCollection;
 use Illuminate\Database\Eloquent\Model;
 
-final class Collection extends BaseCollection
+/**
+ * @template TKey of array-key
+ * @template TModel of Model&Node 
+ *
+ * @extends EloquentCollection<TKey, TModel>
+ */
+final class Collection extends EloquentCollection
 {
 	/**
 	 * Fill `parent` and `children` relationships for every node in the collection.
@@ -20,7 +26,9 @@ public function linkNodes()
 			return $this;
 		}
 
-		$groupedNodes = $this->groupBy($this->first()->getParentIdName());
+		/** @var Node */
+		$first = $this->first();
+		$groupedNodes = $this->groupBy($first->getParentIdName());
 
 		/** @var Node&Model $node */
 		foreach ($this->items as $node) {
@@ -28,14 +36,14 @@ public function linkNodes()
 				$node->setRelation('parent', null);
 			}
 
+			/** @var array<int,Model&Node> */
 			$children = $groupedNodes->get($node->getKey(), []);
 
-			/** @var Model&Node $child */
 			foreach ($children as $child) {
 				$child->setRelation('parent', $node);
 			}
 
-			$node->setRelation('children', BaseCollection::make($children));
+			$node->setRelation('children', EloquentCollection::make($children));
 		}
 
 		return $this;
@@ -77,7 +85,7 @@ public function toTree($root = false)
 	/**
 	 * @param mixed $root
 	 *
-	 * @return int|string|null
+	 * @return int|string
 	 */
 	protected function getRootNodeId($root = false)
 	{
@@ -101,6 +109,10 @@ protected function getRootNodeId($root = false)
 			}
 		}
 
+		if ($root === null || $root === false) {
+			throw new NestedSetException('root is null or false.');
+		}
+
 		return $root;
 	}
 
@@ -110,17 +122,20 @@ protected function getRootNodeId($root = false)
 	 *
 	 * @param bool $root
 	 *
-	 * @return static
+	 * @return Collection
 	 */
-	public function toFlatTree($root = false)
+	public function toFlatTree($root = false): Collection
 	{
-		$result = new static();
+		$result = new Collection();
 
 		if ($this->isEmpty()) {
 			return $result;
 		}
 
-		$groupedNodes = $this->groupBy($this->first()->getParentIdName());
+		/** @var Node */
+		$first = $this->first();
+		/** @var Collection<int|string,TModel> */
+		$groupedNodes = $this->groupBy($first->getParentIdName());
 
 		return $result->flattenTree($groupedNodes, $this->getRootNodeId($root));
 	}
@@ -128,14 +143,16 @@ public function toFlatTree($root = false)
 	/**
 	 * Flatten a tree into a non recursive array.
 	 *
-	 * @param Collection $groupedNodes
-	 * @param mixed      $parentId
+	 * @param Collection<int|string,TModel> $groupedNodes
+	 * @param int|string $parentId
 	 *
-	 * @return $this
+	 * @return Collection
 	 */
-	protected function flattenTree(self $groupedNodes, $parentId)
+	protected function flattenTree(Collection $groupedNodes, $parentId): Collection
 	{
-		foreach ($groupedNodes->get($parentId, []) as $node) {
+		/** @var array<int,TModel> */
+		$nodes = $groupedNodes->get($parentId, []);
+		foreach ($nodes as $node) {
 			$this->push($node);
 
 			$this->flattenTree($groupedNodes, $node->getKey());
diff --git a/src/DescendantsRelation.php b/src/DescendantsRelation.php
index 185e73d..89039cf 100644
--- a/src/DescendantsRelation.php
+++ b/src/DescendantsRelation.php
@@ -4,6 +4,9 @@
 
 use Illuminate\Database\Eloquent\Model;
 
+/**
+ * @disregard P1037
+ */
 class DescendantsRelation extends BaseRelation
 {
 	/**
@@ -31,12 +34,12 @@ protected function addEagerConstraint($query, $model)
 	}
 
 	/**
-	 * @param Model $model
-	 * @param       $related
+	 * @param Model&Node $model
+	 * @param Node $related
 	 *
-	 * @return mixed
+	 * @return bool
 	 */
-	protected function matches(Model $model, $related)
+	protected function matches(Model $model, $related): bool
 	{
 		return $related->isDescendantOf($model);
 	}
diff --git a/src/NestedSetException.php b/src/NestedSetException.php
new file mode 100644
index 0000000..7df7aeb
--- /dev/null
+++ b/src/NestedSetException.php
@@ -0,0 +1,15 @@
+<?php
+
+namespace Kalnoy\Nestedset;
+
+use Throwable;
+
+/**
+ * Exception thrown when something really went wrong.
+ */
+class NestedSetException extends \Exception {
+
+	public function __construct(string $message, ?Throwable $previous = null) {
+        parent::__construct($message, 0, $previous);
+	}
+}
\ No newline at end of file
diff --git a/src/NestedSetServiceProvider.php b/src/NestedSetServiceProvider.php
index 2a14169..e83fb38 100644
--- a/src/NestedSetServiceProvider.php
+++ b/src/NestedSetServiceProvider.php
@@ -10,10 +10,12 @@ class NestedSetServiceProvider extends ServiceProvider
 	public function register()
 	{
 		Blueprint::macro('nestedSet', function () {
+			/** @disregard P1006 */
 			NestedSet::columns($this);
 		});
 
 		Blueprint::macro('dropNestedSet', function () {
+			/** @disregard P1006 */
 			NestedSet::dropColumns($this);
 		});
 	}
diff --git a/src/Node.php b/src/Node.php
index 5cbde7d..b44a0a0 100644
--- a/src/Node.php
+++ b/src/Node.php
@@ -5,7 +5,6 @@
 use Illuminate\Database\Eloquent\Collection as EloquentCollection;
 use Illuminate\Database\Eloquent\Relations\BelongsTo;
 use Illuminate\Database\Eloquent\Relations\HasMany;
-use Illuminate\Support\Collection;
 
 /**
  * Accompanies {@link \Kalnoy\Nestedset\NodeTrait}.
@@ -18,9 +17,17 @@
  * This interface is mandatory such that
  * {@link \Kalnoy\Nestedset\NestedSet::isNode()} recognizes an object as a
  * node.
+ * 
+ * @template Tmodelkey
+ * @template Tmodel of \Illuminate\Database\Eloquent\Model
  */
 interface Node
 {
+	/**
+	 * Refresh node's crucial attributes.
+	 */
+	public function refreshNode(): void;
+
 	/**
 	 * Relation to the parent.
 	 *
@@ -45,14 +52,14 @@ public function descendants(): DescendantsRelation;
 	/**
 	 * Get query for siblings of the node.
 	 *
-	 * @return QueryBuilder
+	 * @return QueryBuilder<Tmodelkey,Tmodel>
 	 */
 	public function siblings(): QueryBuilder;
 
 	/**
 	 * Get the node siblings and the node itself.
 	 *
-	 * @return QueryBuilder
+	 * @return QueryBuilder<Tmodelkey,Tmodel>
 	 */
 	public function siblingsAndSelf(): QueryBuilder;
 
@@ -68,28 +75,28 @@ public function getSiblingsAndSelf(array $columns = ['*']): EloquentCollection;
 	/**
 	 * Get query for siblings after the node.
 	 *
-	 * @return QueryBuilder
+	 * @return QueryBuilder<Tmodelkey,Tmodel>
 	 */
 	public function nextSiblings(): QueryBuilder;
 
 	/**
 	 * Get query for siblings before the node.
 	 *
-	 * @return QueryBuilder
+	 * @return QueryBuilder<Tmodelkey,Tmodel>
 	 */
 	public function prevSiblings(): QueryBuilder;
 
 	/**
 	 * Get query for nodes after current node.
 	 *
-	 * @return QueryBuilder
+	 * @return QueryBuilder<Tmodelkey,Tmodel>
 	 */
 	public function nextNodes(): QueryBuilder;
 
 	/**
 	 * Get query for nodes before current node in reversed order.
 	 *
-	 * @return QueryBuilder
+	 * @return QueryBuilder<Tmodelkey,Tmodel>
 	 */
 	public function prevNodes(): QueryBuilder;
 
@@ -115,13 +122,13 @@ public function makeRoot(): Node;
 	public function saveAsRoot(): bool;
 
 	/**
-	 * @param int             $lft
-	 * @param int             $rgt
-	 * @param int|string|null $parentId
+	 * @param int  $lft
+	 * @param int  $rgt
+	 * @param Tmodelkey $parentId
 	 *
 	 * @return $this
 	 */
-	public function rawNode(int $lft, int $rgt, int|string|null $parentId): Node;
+	public function rawNode(int $lft, int $rgt, mixed $parentId): Node;
 
 	/**
 	 * Move node up given amount of positions.
@@ -151,14 +158,14 @@ public function newEloquentBuilder(QueryBuilder $query): QueryBuilder;
 	 *
 	 * @since 1.1
 	 *
-	 * @return QueryBuilder
+	 * @return QueryBuilder<Tmodelkey,Tmodel>
 	 */
-	public function newNestedSetQuery(?QueryBuilder $table = null): QueryBuilder;
+	public function newNestedSetQuery(QueryBuilder|string|null $table = null): QueryBuilder;
 
 	/**
 	 * @param ?string $table
 	 *
-	 * @return QueryBuilder
+	 * @return QueryBuilder<Tmodelkey,Tmodel>
 	 */
 	public function newScopedQuery($table = null);
 
@@ -173,16 +180,14 @@ public function applyNestedSetScope($query, $table = null);
 	/**
 	 * @param string[] $attributes
 	 *
-	 * @return QueryBuilder
+	 * @return QueryBuilder<Tmodelkey,Tmodel>
 	 */
 	public static function scoped(array $attributes): QueryBuilder;
 
 	/**
-	 * @template Tmodel of \Illuminate\Database\Eloquent\Model
+	 * @param array<int,Tmodel&Node> $models
 	 *
-	 * @param array<int,Tmodel> $models
-	 *
-	 * @return Collection
+	 * @return Collection<int,Tmodel&Node<Tmodelkey,Tmodel>>
 	 */
 	public function newCollection(array $models = []): Collection;
 
@@ -201,11 +206,11 @@ public function getDescendantCount(): int;
 	 *
 	 * Behind the scenes node is appended to found parent node.
 	 *
-	 * @param int|string|null $value
+	 * @param Tmodelkey|null $value
 	 *
 	 * @throws \Exception If parent node doesn't exists
 	 */
-	public function setParentIdAttribute(int|string|null $value): void;
+	public function setParentIdAttribute(mixed $value): void;
 
 	/**
 	 * Get whether node is root.
@@ -242,9 +247,9 @@ public function getRgt(): int|null;
 	/**
 	 * Get the value of the model's parent id key.
 	 *
-	 * @return int|string|null
+	 * @return Tmodelkey|null
 	 */
-	public function getParentId(): int|string|null;
+	public function getParentId(): mixed;
 
 	/**
 	 * Returns node that is next to current node without constraining to siblings.
@@ -325,28 +330,90 @@ public function getBounds();
 	/**
 	 * @param $value
 	 *
-	 * @return $this
+	 * @return Node&Tmodel
 	 */
 	public function setLft(int $value): Node;
 
 	/**
 	 * @param $value
 	 *
-	 * @return $this
+	 * @return Node&Tmodel
 	 */
 	public function setRgt(int $value): Node;
 
 	/**
-	 * @param $value
+	 * @param Tmodelkey|null $id
 	 *
-	 * @return $this
+	 * @return Node&Tmodel
 	 */
-	public function setParentId(int|string|null $value): Node;
+	public function setParentId(mixed $id): Node;
 
 	/**
 	 * @param string[]|null $except
 	 *
-	 * @return $this
+	 * @return Node
 	 */
 	public function replicate(?array $except = null): Node;
+
+
+	/**
+	 * Append and save a node.
+	 *
+	 * @param Node&Tmodel $node
+	 *
+	 * @return bool
+	 */
+	public function appendNode(Node $node): bool;
+
+	/**
+	 * Append a node to the new parent.
+	 *
+	 * @param Node&Tmodel $parent
+	 *
+	 * @return Node&Tmodel
+	 */
+	public function appendToNode(Node $parent): Node;
+
+	/**
+	 * Prepend a node to the new parent.
+	 *
+	 * @param Node $parent
+	 *
+	 * @return Node&Tmodel
+	 */
+	public function prependToNode(Node $parent): Node;
+
+	/**
+	 * Get whether the node is an ancestor of other node, including immediate parent.
+	 *
+	 * @param Node $other
+	 *
+	 * @return bool
+	 */
+	public function isAncestorOf(Node $other): bool;
+
+	/**
+	 * Get whether a node is a descendant of other node.
+	 *
+	 * @param Node $other
+	 *
+	 * @return bool
+	 */
+	public function isDescendantOf(Node $other): bool;
+
+	/**
+	 * Get whether a node is itself or a descendant of other node.
+	 *
+	 * @param Node $other
+	 *
+	 * @return bool
+	 */
+	public function isSelfOrDescendantOf(Node $other);
+
+	/**
+	 * Create a new Query
+	 * 
+	 * @return QueryBuilder
+	 */
+	public function newQuery();
 }
diff --git a/src/NodeTrait.php b/src/NodeTrait.php
index f23c088..818566d 100644
--- a/src/NodeTrait.php
+++ b/src/NodeTrait.php
@@ -9,6 +9,10 @@
 use Illuminate\Database\Eloquent\Relations\HasMany;
 use Illuminate\Support\Arr;
 
+/**
+ * @template Tmodelkey
+ * @template Tmodel extends Model
+ */
 trait NodeTrait
 {
 	/**
@@ -63,7 +67,7 @@ public static function bootNodeTrait(): void
 	 *
 	 * @return $this
 	 */
-	protected function setNodeAction($action): self
+	protected function setNodeAction($action): Node
 	{
 		$this->pending = func_get_args();
 
@@ -146,12 +150,12 @@ protected function getLowerBound(): int
 	/**
 	 * Append or prepend a node to the parent.
 	 *
-	 * @param self $parent
+	 * @param Node $parent
 	 * @param bool $prepend
 	 *
 	 * @return bool
 	 */
-	protected function actionAppendOrPrepend(self $parent, $prepend = false)
+	protected function actionAppendOrPrepend(Node $parent, $prepend = false)
 	{
 		$parent->refreshNode();
 
@@ -184,12 +188,12 @@ protected function setParent($value)
 	/**
 	 * Insert node before or after another node.
 	 *
-	 * @param self $node
+	 * @param Node $node
 	 * @param bool $after
 	 *
 	 * @return bool
 	 */
-	protected function actionBeforeOrAfter(self $node, $after = false)
+	protected function actionBeforeOrAfter(Node $node, $after = false)
 	{
 		$node->refreshNode();
 
@@ -199,7 +203,7 @@ protected function actionBeforeOrAfter(self $node, $after = false)
 	/**
 	 * Refresh node's crucial attributes.
 	 */
-	public function refreshNode()
+	public function refreshNode(): void
 	{
 		if (!$this->exists || static::$actionsPerformed === 0) {
 			return;
@@ -361,23 +365,24 @@ public function saveAsRoot(): bool
 	/**
 	 * Append and save a node.
 	 *
-	 * @param self $node
+	 * @param Node&Tmodel $node
 	 *
 	 * @return bool
 	 */
-	public function appendNode(self $node): bool
+	public function appendNode(Node $node): bool
 	{
+		/** @disregard P1013 */
 		return $node->appendToNode($this)->save();
 	}
 
 	/**
 	 * Prepend and save a node.
 	 *
-	 * @param self $node
+	 * @param Node $node
 	 *
 	 * @return bool
 	 */
-	public function prependNode(self $node): bool
+	public function prependNode(Node $node): bool
 	{
 		return $node->prependToNode($this)->save();
 	}
@@ -385,11 +390,11 @@ public function prependNode(self $node): bool
 	/**
 	 * Append a node to the new parent.
 	 *
-	 * @param self $parent
+	 * @param Node&Tmodel $parent
 	 *
-	 * @return $this
+	 * @return Node&Tmodel
 	 */
-	public function appendToNode(self $parent): self
+	public function appendToNode(Node $parent): Node
 	{
 		return $this->appendOrPrependTo($parent);
 	}
@@ -397,22 +402,22 @@ public function appendToNode(self $parent): self
 	/**
 	 * Prepend a node to the new parent.
 	 *
-	 * @param self $parent
+	 * @param Node $parent
 	 *
 	 * @return $this
 	 */
-	public function prependToNode(self $parent): self
+	public function prependToNode(Node $parent): Node
 	{
 		return $this->appendOrPrependTo($parent, true);
 	}
 
 	/**
-	 * @param self $parent
+	 * @param Node $parent
 	 * @param bool $prepend
 	 *
-	 * @return self
+	 * @return Node
 	 */
-	public function appendOrPrependTo(self $parent, $prepend = false)
+	public function appendOrPrependTo(Node $parent, bool $prepend = false)
 	{
 		$this->assertNodeExists($parent)
 			->assertNotDescendant($parent)
@@ -426,11 +431,11 @@ public function appendOrPrependTo(self $parent, $prepend = false)
 	/**
 	 * Insert self after a node.
 	 *
-	 * @param self $node
+	 * @param Node $node
 	 *
 	 * @return $this
 	 */
-	public function afterNode(self $node)
+	public function afterNode(Node $node)
 	{
 		return $this->beforeOrAfterNode($node, true);
 	}
@@ -438,22 +443,22 @@ public function afterNode(self $node)
 	/**
 	 * Insert self before node.
 	 *
-	 * @param self $node
+	 * @param Node $node
 	 *
 	 * @return $this
 	 */
-	public function beforeNode(self $node)
+	public function beforeNode(Node $node)
 	{
 		return $this->beforeOrAfterNode($node);
 	}
 
 	/**
-	 * @param self $node
+	 * @param Node&Tmodel $node
 	 * @param bool $after
 	 *
-	 * @return self
+	 * @return Node
 	 */
-	public function beforeOrAfterNode(self $node, $after = false)
+	public function beforeOrAfterNode(Node $node, bool $after = false)
 	{
 		$this->assertNodeExists($node)
 			->assertNotDescendant($node)
@@ -471,11 +476,11 @@ public function beforeOrAfterNode(self $node, $after = false)
 	/**
 	 * Insert self after a node and save.
 	 *
-	 * @param self $node
+	 * @param Node $node
 	 *
 	 * @return bool
 	 */
-	public function insertAfterNode(self $node)
+	public function insertAfterNode(Node $node)
 	{
 		return $this->afterNode($node)->save();
 	}
@@ -483,11 +488,11 @@ public function insertAfterNode(self $node)
 	/**
 	 * Insert self before a node and save.
 	 *
-	 * @param self $node
+	 * @param Node $node
 	 *
 	 * @return bool
 	 */
-	public function insertBeforeNode(self $node)
+	public function insertBeforeNode(Node $node)
 	{
 		if (!$this->beforeNode($node)->save()) {
 			return false;
@@ -502,11 +507,11 @@ public function insertBeforeNode(self $node)
 	/**
 	 * @param int             $lft
 	 * @param int             $rgt
-	 * @param int|string|null $parentId
+	 * @param Tmodelkey|null $parentId
 	 *
-	 * @return $this
+	 * @return Node
 	 */
-	public function rawNode(int $lft, int $rgt, int|string|null $parentId): self
+	public function rawNode(int $lft, int $rgt, mixed $parentId): Node
 	{
 		$this->setLft($lft)->setRgt($rgt)->setParentId($parentId);
 
@@ -582,7 +587,7 @@ protected function insertAt($position)
 	 *
 	 * @return int
 	 */
-	protected function moveNode($position)
+	protected function moveNode(int $position)
 	{
 		$updated = $this->newNestedSetQuery()
 				->moveNode($this->getKey(), $position) > 0;
@@ -603,7 +608,7 @@ protected function moveNode($position)
 	 *
 	 * @return bool
 	 */
-	protected function insertNode($position)
+	protected function insertNode(int $position)
 	{
 		$this->newNestedSetQuery()->makeGap($position, 2);
 
@@ -772,9 +777,9 @@ public function newCollection(array $models = []): Collection
 	 *
 	 * Use `children` key on `$attributes` to create child nodes.
 	 *
-	 * @param self $parent
+	 * @param Node $parent
 	 */
-	public static function create(array $attributes = [], ?self $parent = null)
+	public static function create(array $attributes = [], ?Node $parent = null)
 	{
 		$children = Arr::pull($attributes, 'children');
 
@@ -825,18 +830,20 @@ public function getDescendantCount(): int
 	 *
 	 * Behind the scenes node is appended to found parent node.
 	 *
-	 * @param int|string|null $value
+	 * @param Tmodelkey|null $value
 	 *
 	 * @throws \Exception If parent node doesn't exists
 	 */
-	public function setParentIdAttribute(int|string|null $value): void
+	public function setParentIdAttribute(mixed $value): void
 	{
 		if ($this->getParentId() == $value) {
 			return;
 		}
 
 		if ($value) {
-			$this->appendToNode($this->newScopedQuery()->findOrFail($value));
+			/** @var Node&Tmodel */
+			$node = $this->newScopedQuery()->findOrFail($value);
+			$this->appendToNode($node);
 		} else {
 			$this->makeRoot();
 		}
@@ -898,9 +905,9 @@ public function getRgt(): int|null
 	/**
 	 * Get the value of the model's parent id key.
 	 *
-	 * @return int|string|null
+	 * @return Tmodelkey|null
 	 */
-	public function getParentId(): int|string|null
+	public function getParentId(): mixed
 	{
 		return $this->getAttributeValue($this->getParentIdName());
 	}
@@ -912,9 +919,9 @@ public function getParentId(): int|string|null
 	 *
 	 * @param string[] $columns
 	 *
-	 * @return self
+	 * @return Node
 	 */
-	public function getNextNode(array $columns = ['*']): self
+	public function getNextNode(array $columns = ['*']): Node
 	{
 		return $this->nextNodes()->defaultOrder()->first($columns);
 	}
@@ -926,9 +933,9 @@ public function getNextNode(array $columns = ['*']): self
 	 *
 	 * @param string[] $columns
 	 *
-	 * @return self
+	 * @return Node
 	 */
-	public function getPrevNode(array $columns = ['*']): self
+	public function getPrevNode(array $columns = ['*']): Node
 	{
 		return $this->prevNodes()->defaultOrder('desc')->first($columns);
 	}
@@ -946,7 +953,7 @@ public function getAncestors(array $columns = ['*'])
 	/**
 	 * @param string[] $columns
 	 *
-	 * @return Collection|self[]
+	 * @return Collection|Node[]
 	 */
 	public function getDescendants(array $columns = ['*'])
 	{
@@ -956,7 +963,7 @@ public function getDescendants(array $columns = ['*'])
 	/**
 	 * @param string[] $columns
 	 *
-	 * @return Collection|self[]
+	 * @return Collection|Node[]
 	 */
 	public function getSiblings(array $columns = ['*'])
 	{
@@ -966,7 +973,7 @@ public function getSiblings(array $columns = ['*'])
 	/**
 	 * @param string[] $columns
 	 *
-	 * @return Collection|self[]
+	 * @return Collection|Node[]
 	 */
 	public function getNextSiblings(array $columns = ['*'])
 	{
@@ -976,7 +983,7 @@ public function getNextSiblings(array $columns = ['*'])
 	/**
 	 * @param string[] $columns
 	 *
-	 * @return Collection|self[]
+	 * @return Collection|Node[]
 	 */
 	public function getPrevSiblings(array $columns = ['*'])
 	{
@@ -986,7 +993,7 @@ public function getPrevSiblings(array $columns = ['*'])
 	/**
 	 * @param string[] $columns
 	 *
-	 * @return self
+	 * @return Node
 	 */
 	public function getNextSibling(array $columns = ['*'])
 	{
@@ -996,7 +1003,7 @@ public function getNextSibling(array $columns = ['*'])
 	/**
 	 * @param string[] $columns
 	 *
-	 * @return self
+	 * @return Node
 	 */
 	public function getPrevSibling(array $columns = ['*'])
 	{
@@ -1006,11 +1013,11 @@ public function getPrevSibling(array $columns = ['*'])
 	/**
 	 * Get whether a node is a descendant of other node.
 	 *
-	 * @param self $other
+	 * @param Node $other
 	 *
 	 * @return bool
 	 */
-	public function isDescendantOf(self $other)
+	public function isDescendantOf(Node $other): bool
 	{
 		return $this->getLft() > $other->getLft() &&
 			$this->getLft() < $other->getRgt();
@@ -1019,11 +1026,11 @@ public function isDescendantOf(self $other)
 	/**
 	 * Get whether a node is itself or a descendant of other node.
 	 *
-	 * @param self $other
+	 * @param Node $other
 	 *
 	 * @return bool
 	 */
-	public function isSelfOrDescendantOf(self $other)
+	public function isSelfOrDescendantOf(Node $other)
 	{
 		return $this->getLft() >= $other->getLft() &&
 			$this->getLft() < $other->getRgt();
@@ -1032,11 +1039,11 @@ public function isSelfOrDescendantOf(self $other)
 	/**
 	 * Get whether the node is immediate children of other node.
 	 *
-	 * @param self $other
+	 * @param Node&Tmodel $other
 	 *
 	 * @return bool
 	 */
-	public function isChildOf(self $other)
+	public function isChildOf(Node $other)
 	{
 		return $this->getParentId() == $other->getKey();
 	}
@@ -1044,11 +1051,11 @@ public function isChildOf(self $other)
 	/**
 	 * Get whether the node is a sibling of another node.
 	 *
-	 * @param self $other
+	 * @param Node $other
 	 *
 	 * @return bool
 	 */
-	public function isSiblingOf(self $other)
+	public function isSiblingOf(Node $other)
 	{
 		return $this->getParentId() == $other->getParentId();
 	}
@@ -1056,11 +1063,11 @@ public function isSiblingOf(self $other)
 	/**
 	 * Get whether the node is an ancestor of other node, including immediate parent.
 	 *
-	 * @param self $other
+	 * @param Node $other
 	 *
 	 * @return bool
 	 */
-	public function isAncestorOf(self $other)
+	public function isAncestorOf(Node $other): bool
 	{
 		return $other->isDescendantOf($this);
 	}
@@ -1068,11 +1075,11 @@ public function isAncestorOf(self $other)
 	/**
 	 * Get whether the node is itself or an ancestor of other node, including immediate parent.
 	 *
-	 * @param self $other
+	 * @param Node $other
 	 *
 	 * @return bool
 	 */
-	public function isSelfOrAncestorOf(self $other)
+	public function isSelfOrAncestorOf(Node $other)
 	{
 		return $other->isSelfOrDescendantOf($this);
 	}
@@ -1121,9 +1128,9 @@ public function getBounds()
 	/**
 	 * @param $value
 	 *
-	 * @return self $this
+	 * @return Node $this
 	 */
-	public function setLft(int $value): self
+	public function setLft(int $value): Node
 	{
 		$this->attributes[$this->getLftName()] = $value;
 
@@ -1133,9 +1140,9 @@ public function setLft(int $value): self
 	/**
 	 * @param $value
 	 *
-	 * @return self $this
+	 * @return Node $this
 	 */
-	public function setRgt(int $value): self
+	public function setRgt(int $value): Node
 	{
 		$this->attributes[$this->getRgtName()] = $value;
 
@@ -1143,11 +1150,11 @@ public function setRgt(int $value): self
 	}
 
 	/**
-	 * @param int|string|null $value
+	 * @param Tmodelkey|null $value
 	 *
-	 * @return self $this
+	 * @return Node&Tmodel
 	 */
-	public function setParentId(int|string|null $value): self
+	public function setParentId(mixed $value): Node
 	{
 		$this->attributes[$this->getParentIdName()] = $value;
 
@@ -1155,7 +1162,7 @@ public function setParentId(int|string|null $value): self
 	}
 
 	/**
-	 * @return $this
+	 * @return Node
 	 */
 	protected function dirtyBounds()
 	{
@@ -1166,11 +1173,11 @@ protected function dirtyBounds()
 	}
 
 	/**
-	 * @param self $node
+	 * @param Node $node
 	 *
-	 * @return $this
+	 * @return Node
 	 */
-	protected function assertNotDescendant(self $node)
+	protected function assertNotDescendant(Node $node)
 	{
 		if ($node == $this || $node->isDescendantOf($this)) {
 			throw new \LogicException('Node must not be a descendant.');
@@ -1180,11 +1187,11 @@ protected function assertNotDescendant(self $node)
 	}
 
 	/**
-	 * @param self $node
+	 * @param Node $node
 	 *
-	 * @return $this
+	 * @return Node&Tmodel
 	 */
-	protected function assertNodeExists(self $node)
+	protected function assertNodeExists(Node $node)
 	{
 		if (!$node->getLft() || !$node->getRgt()) {
 			throw new \LogicException('Node must exists.');
@@ -1194,9 +1201,9 @@ protected function assertNodeExists(self $node)
 	}
 
 	/**
-	 * @param self $node
+	 * @param Node&Tmodel $node
 	 */
-	protected function assertSameScope(self $node)
+	protected function assertSameScope(Node $node): void
 	{
 		if (!$scoped = $this->getScopeAttributes()) {
 			return;
@@ -1214,7 +1221,7 @@ protected function assertSameScope(self $node)
 	 *
 	 * @return \Illuminate\Database\Eloquent\Model
 	 */
-	public function replicate(?array $except = null): self
+	public function replicate(?array $except = null): Node
 	{
 		$defaults = [
 			$this->getParentIdName(),
diff --git a/src/QueryBuilder.php b/src/QueryBuilder.php
index 934bb01..76ec9c0 100644
--- a/src/QueryBuilder.php
+++ b/src/QueryBuilder.php
@@ -3,6 +3,7 @@
 namespace Kalnoy\Nestedset;
 
 use Illuminate\Database\Eloquent\Builder;
+use Illuminate\Database\Eloquent\Collection as EloquentCollection;
 use Illuminate\Database\Eloquent\Model;
 use Illuminate\Database\Eloquent\ModelNotFoundException;
 use Illuminate\Database\Query\Builder as BaseQueryBuilder;
@@ -10,10 +11,17 @@
 use Illuminate\Database\Query\Expression;
 use Illuminate\Support\Arr;
 
+/**
+ * @template Tmodelkey
+ * @template Tmodel of \Illuminate\Database\Eloquent\Model
+ * 
+ * @phpstan-type NodeModel Node<Tmodelkey,Tmodel>&Tmodel
+ * @extends Builder<NodeModel>
+ */
 class QueryBuilder extends Builder
 {
 	/**
-	 * @var Node&Model
+	 * @var NodeModel
 	 */
 	protected $model;
 
@@ -22,12 +30,12 @@ class QueryBuilder extends Builder
 	 *
 	 * @since 2.0
 	 *
-	 * @param mixed $id
+	 * @param Tmodelkey  $id
 	 * @param bool  $required
 	 *
-	 * @return array
+	 * @return array<int,int>
 	 */
-	public function getNodeData($id, $required = false)
+	public function getNodeData(mixed $id, $required = false)
 	{
 		$query = $this->toBase();
 
@@ -36,7 +44,7 @@ public function getNodeData($id, $required = false)
 		$data = $query->first([$this->model->getLftName(),
 			$this->model->getRgtName(), ]);
 
-		if (!$data && $required) {
+		if ($data === null && $required) {
 			throw new ModelNotFoundException();
 		}
 
@@ -48,12 +56,12 @@ public function getNodeData($id, $required = false)
 	 *
 	 * @since 2.0
 	 *
-	 * @param mixed $id
+	 * @param Tmodelkey $id
 	 * @param bool  $required
 	 *
-	 * @return array
+	 * @return array<int,int>
 	 */
-	public function getPlainNodeData($id, $required = false)
+	public function getPlainNodeData(mixed $id, $required = false)
 	{
 		return array_values($this->getNodeData($id, $required));
 	}
@@ -61,9 +69,9 @@ public function getPlainNodeData($id, $required = false)
 	/**
 	 * Scope limits query to select just root node.
 	 *
-	 * @return $this
+	 * @return QueryBuilder<Tmodelkey,Tmodel>
 	 */
-	public function whereIsRoot()
+	public function whereIsRoot(): QueryBuilder
 	{
 		$this->query->whereNull($this->model->getParentIdName());
 
@@ -75,13 +83,13 @@ public function whereIsRoot()
 	 *
 	 * @since 2.0
 	 *
-	 * @param mixed  $id
+	 * @param Tmodelkey  $id
 	 * @param bool   $andSelf
 	 * @param string $boolean
 	 *
-	 * @return $this
+	 * @return QueryBuilder<Tmodelkey,Tmodel>
 	 */
-	public function whereAncestorOf($id, $andSelf = false, $boolean = 'and')
+	public function whereAncestorOf(mixed $id, bool $andSelf = false, string $boolean = 'and')
 	{
 		$keyName = $this->model->getTable() . '.' . $this->model->getKeyName();
 
@@ -120,22 +128,22 @@ public function whereAncestorOf($id, $andSelf = false, $boolean = 'and')
 	}
 
 	/**
-	 * @param      $id
+	 * @param Tmodelkey $id
 	 * @param bool $andSelf
 	 *
-	 * @return $this
+	 * @return QueryBuilder<Tmodelkey,Tmodel>
 	 */
-	public function orWhereAncestorOf($id, $andSelf = false)
+	public function orWhereAncestorOf(mixed $id, $andSelf = false): QueryBuilder
 	{
 		return $this->whereAncestorOf($id, $andSelf, 'or');
 	}
 
 	/**
-	 * @param $id
+	 * @param Tmodelkey $id
 	 *
-	 * @return QueryBuilder
+	 * @return QueryBuilder<Tmodelkey,Tmodel>
 	 */
-	public function whereAncestorOrSelf($id)
+	public function whereAncestorOrSelf(mixed $id): QueryBuilder
 	{
 		return $this->whereAncestorOf($id, true);
 	}
@@ -145,23 +153,23 @@ public function whereAncestorOrSelf($id)
 	 *
 	 * @since 2.0
 	 *
-	 * @param mixed $id
-	 * @param array $columns
+	 * @param Tmodelkey $id
+	 * @param string[] $columns
 	 *
-	 * @return \Kalnoy\Nestedset\Collection
+	 * @return EloquentCollection<int,NodeModel>
 	 */
-	public function ancestorsOf($id, array $columns = ['*'])
+	public function ancestorsOf(mixed $id, array $columns = ['*'])
 	{
 		return $this->whereAncestorOf($id)->get($columns);
 	}
 
 	/**
-	 * @param       $id
-	 * @param array $columns
+	 * @param Tmodelkey      $id
+	 * @param string[] $columns
 	 *
-	 * @return \Kalnoy\Nestedset\Collection
+	 * @return EloquentCollection<int,NodeModel>
 	 */
-	public function ancestorsAndSelf($id, array $columns = ['*'])
+	public function ancestorsAndSelf(mixed $id, array $columns = ['*'])
 	{
 		return $this->whereAncestorOf($id, true)->get($columns);
 	}
@@ -171,13 +179,13 @@ public function ancestorsAndSelf($id, array $columns = ['*'])
 	 *
 	 * @since 2.0
 	 *
-	 * @param array  $values
+	 * @param int[]  $values
 	 * @param string $boolean
 	 * @param bool   $not
 	 *
-	 * @return $this
+	 * @return QueryBuilder<Tmodelkey,Tmodel>
 	 */
-	public function whereNodeBetween($values, $boolean = 'and', $not = false)
+	public function whereNodeBetween(array $values, $boolean = 'and', $not = false)
 	{
 		$this->query->whereBetween($this->model->getTable() . '.' . $this->model->getLftName(), $values, $boolean, $not);
 
@@ -189,11 +197,11 @@ public function whereNodeBetween($values, $boolean = 'and', $not = false)
 	 *
 	 * @since 2.0
 	 *
-	 * @param array $values
+	 * @param int[] $values
 	 *
-	 * @return $this
+	 * @return QueryBuilder<Tmodelkey,Tmodel>
 	 */
-	public function orWhereNodeBetween($values)
+	public function orWhereNodeBetween(array $values)
 	{
 		return $this->whereNodeBetween($values, 'or');
 	}
@@ -203,14 +211,14 @@ public function orWhereNodeBetween($values)
 	 *
 	 * @since 2.0
 	 *
-	 * @param mixed  $id
+	 * @param Tmodelkey  $id
 	 * @param string $boolean
 	 * @param bool   $not
 	 * @param bool   $andSelf
 	 *
-	 * @return $this
+	 * @return QueryBuilder<Tmodelkey,Tmodel>
 	 */
-	public function whereDescendantOf($id, $boolean = 'and', $not = false,
+	public function whereDescendantOf(mixed $id, $boolean = 'and', $not = false,
 		$andSelf = false
 	) {
 		if (NestedSet::isNode($id)) {
@@ -229,43 +237,43 @@ public function whereDescendantOf($id, $boolean = 'and', $not = false,
 	}
 
 	/**
-	 * @param mixed $id
+	 * @param Tmodelkey $id
 	 *
 	 * @return QueryBuilder
 	 */
-	public function whereNotDescendantOf($id)
+	public function whereNotDescendantOf(mixed $id)
 	{
 		return $this->whereDescendantOf($id, 'and', true);
 	}
 
 	/**
-	 * @param mixed $id
+	 * @param Tmodelkey $id
 	 *
 	 * @return QueryBuilder
 	 */
-	public function orWhereDescendantOf($id)
+	public function orWhereDescendantOf(mixed $id)
 	{
 		return $this->whereDescendantOf($id, 'or');
 	}
 
 	/**
-	 * @param mixed $id
+	 * @param Tmodelkey $id
 	 *
 	 * @return QueryBuilder
 	 */
-	public function orWhereNotDescendantOf($id)
+	public function orWhereNotDescendantOf(mixed $id)
 	{
 		return $this->whereDescendantOf($id, 'or', true);
 	}
 
 	/**
-	 * @param        $id
+	 * @param  Tmodelkey  $id
 	 * @param string $boolean
 	 * @param bool   $not
 	 *
-	 * @return $this
+	 * @return QueryBuilder<Tmodelkey,Tmodel>
 	 */
-	public function whereDescendantOrSelf($id, $boolean = 'and', $not = false)
+	public function whereDescendantOrSelf(mixed $id, string $boolean = 'and', bool $not = false)
 	{
 		return $this->whereDescendantOf($id, $boolean, $not, true);
 	}
@@ -275,13 +283,13 @@ public function whereDescendantOrSelf($id, $boolean = 'and', $not = false)
 	 *
 	 * @since 2.0
 	 *
-	 * @param mixed $id
-	 * @param array $columns
+	 * @param Tmodelkey $id
+	 * @param string[] $columns
 	 * @param bool  $andSelf
 	 *
-	 * @return Collection
+	 * @return EloquentCollection<int,NodeModel>
 	 */
-	public function descendantsOf($id, array $columns = ['*'], $andSelf = false)
+	public function descendantsOf(mixed $id, array $columns = ['*'], bool $andSelf = false)
 	{
 		try {
 			return $this->whereDescendantOf($id, 'and', false, $andSelf)->get($columns);
@@ -291,10 +299,10 @@ public function descendantsOf($id, array $columns = ['*'], $andSelf = false)
 	}
 
 	/**
-	 * @param       $id
-	 * @param array $columns
+	 * @param Tmodelkey $id
+	 * @param string[] $columns
 	 *
-	 * @return Collection
+	 * @return EloquentCollection<int,NodeModel>
 	 */
 	public function descendantsAndSelf($id, array $columns = ['*'])
 	{
@@ -302,13 +310,13 @@ public function descendantsAndSelf($id, array $columns = ['*'])
 	}
 
 	/**
-	 * @param $id
-	 * @param $operator
-	 * @param $boolean
+	 * @param Tmodelkey $id
+	 * @param string $operator
+	 * @param string $boolean
 	 *
-	 * @return $this
+	 * @return QueryBuilder<Tmodelkey,Tmodel>
 	 */
-	protected function whereIsBeforeOrAfter($id, $operator, $boolean)
+	protected function whereIsBeforeOrAfter(mixed $id, string $operator, string $boolean)
 	{
 		if (NestedSet::isNode($id)) {
 			$value = '?';
@@ -339,10 +347,10 @@ protected function whereIsBeforeOrAfter($id, $operator, $boolean)
 	 *
 	 * @since 2.0
 	 *
-	 * @param mixed  $id
+	 * @param Tmodelkey  $id
 	 * @param string $boolean
 	 *
-	 * @return $this
+	 * @return QueryBuilder<Tmodelkey,Tmodel>
 	 */
 	public function whereIsAfter($id, $boolean = 'and')
 	{
@@ -354,10 +362,10 @@ public function whereIsAfter($id, $boolean = 'and')
 	 *
 	 * @since 2.0
 	 *
-	 * @param mixed  $id
+	 * @param Tmodelkey  $id
 	 * @param string $boolean
 	 *
-	 * @return $this
+	 * @return QueryBuilder<Tmodelkey,Tmodel>
 	 */
 	public function whereIsBefore($id, $boolean = 'and')
 	{
@@ -365,19 +373,19 @@ public function whereIsBefore($id, $boolean = 'and')
 	}
 
 	/**
-	 * @return $this
+	 * @return QueryBuilder<Tmodelkey,Tmodel>
 	 */
 	public function whereIsLeaf()
 	{
 		list($lft, $rgt) = $this->wrappedColumns();
 
-		return $this->whereRaw("$lft = $rgt - 1");
+		return $this->whereRaw("$lft = $rgt - 1"); /** @phpstan-ignore-line */
 	}
 
 	/**
-	 * @param array $columns
+	 * @param string[] $columns
 	 *
-	 * @return Collection
+	 * @return EloquentCollection<int,NodeModel>
 	 */
 	public function leaves(array $columns = ['*'])
 	{
@@ -389,7 +397,7 @@ public function leaves(array $columns = ['*'])
 	 *
 	 * @param string $as
 	 *
-	 * @return $this
+	 * @return QueryBuilder<Tmodelkey,Tmodel>
 	 */
 	public function withDepth($as = 'depth')
 	{
@@ -421,9 +429,9 @@ public function withDepth($as = 'depth')
 	 *
 	 * @since 2.0
 	 *
-	 * @return array
+	 * @return string[]
 	 */
-	protected function wrappedColumns()
+	protected function wrappedColumns(): array
 	{
 		$grammar = $this->query->getGrammar();
 
@@ -440,7 +448,7 @@ protected function wrappedColumns()
 	 *
 	 * @return string
 	 */
-	protected function wrappedTable()
+	protected function wrappedTable(): string
 	{
 		return $this->query->getGrammar()->wrapTable($this->getQuery()->from);
 	}
@@ -452,7 +460,7 @@ protected function wrappedTable()
 	 *
 	 * @return string
 	 */
-	protected function wrappedKey()
+	protected function wrappedKey(): string
 	{
 		return $this->query->getGrammar()->wrap($this->model->getKeyName());
 	}
@@ -460,9 +468,9 @@ protected function wrappedKey()
 	/**
 	 * Exclude root node from the result.
 	 *
-	 * @return $this
+	 * @return QueryBuilder<Tmodelkey,Tmodel>
 	 */
-	public function withoutRoot()
+	public function withoutRoot(): QueryBuilder
 	{
 		$this->query->whereNotNull($this->model->getParentIdName());
 
@@ -475,9 +483,9 @@ public function withoutRoot()
 	 * @since 2.0
 	 * @deprecated since v4.1
 	 *
-	 * @return $this
+	 * @return QueryBuilder<Tmodelkey,Tmodel>
 	 */
-	public function hasParent()
+	public function hasParent(): QueryBuilder
 	{
 		$this->query->whereNotNull($this->model->getParentIdName());
 
@@ -490,9 +498,9 @@ public function hasParent()
 	 * @since 2.0
 	 * @deprecated since v4.1
 	 *
-	 * @return $this
+	 * @return QueryBuilder<Tmodelkey,Tmodel>
 	 */
-	public function hasChildren()
+	public function hasChildren(): QueryBuilder
 	{
 		list($lft, $rgt) = $this->wrappedColumns();
 
@@ -506,9 +514,9 @@ public function hasChildren()
 	 *
 	 * @param string $dir
 	 *
-	 * @return $this
+	 * @return QueryBuilder<Tmodelkey,Tmodel>
 	 */
-	public function defaultOrder($dir = 'asc')
+	public function defaultOrder($dir = 'asc'): QueryBuilder
 	{
 		$this->query->orders = [];
 
@@ -520,9 +528,9 @@ public function defaultOrder($dir = 'asc')
 	/**
 	 * Order by reversed node position.
 	 *
-	 * @return $this
+	 * @return QueryBuilder<Tmodelkey,Tmodel>
 	 */
-	public function reversed()
+	public function reversed(): QueryBuilder
 	{
 		return $this->defaultOrder('desc');
 	}
@@ -604,11 +612,11 @@ public function makeGap($cut, $height)
 	 *
 	 * @since 2.0
 	 *
-	 * @param array $params
+	 * @param array{height:int,cut?:int,distance?:int,lft?:int,rgt?:int,to?:int,from?:int} $params
 	 *
-	 * @return array
+	 * @return array<string,Expression>
 	 */
-	protected function patch(array $params)
+	protected function patch(array $params): array
 	{
 		$grammar = $this->query->getGrammar();
 
@@ -627,15 +635,14 @@ protected function patch(array $params)
 	 * @since 2.0
 	 *
 	 * @param string $col
-	 * @param array  $params
+	 * @param array{height:int,cut?:int,distance?:int,lft?:int,rgt?:int,to?:int,from?:int}  $params
 	 *
-	 * @return string
+	 * @return Expression
 	 */
-	protected function columnPatch($col, array $params)
+	protected function columnPatch(string $col, array $params): Expression
 	{
 		extract($params);
 
-		/** @var int $height */
 		if ($height > 0) {
 			$height = '+' . $height;
 		}
@@ -644,11 +651,11 @@ protected function columnPatch($col, array $params)
 			return new Expression("case when {$col} >= {$cut} then {$col}{$height} else {$col} end");
 		}
 
-		/** @var int $distance */
-		/** @var int $lft */
-		/** @var int $rgt */
-		/** @var int $from */
-		/** @var int $to */
+		if (!isset($distance) || !isset($lft) || !isset($rgt) || !isset($to) || !isset($from))
+		{
+			throw new NestedSetException('Incorrect Parameters');
+		}
+
 		if ($distance > 0) {
 			$distance = '+' . $distance;
 		}
@@ -784,7 +791,7 @@ protected function getWrongParentQuery()
 	}
 
 	/**
-	 * @return $this
+	 * @return QueryBuilder<Tmodelkey,Tmodel>
 	 */
 	protected function getMissingParentQuery()
 	{
@@ -844,7 +851,7 @@ public function isBroken()
 	 *
 	 * Nodes with invalid parent are saved as roots.
 	 *
-	 * @param NodeTrait|Model|null $root
+	 * @param (Model&Node)|null $root
 	 *
 	 * @return int The number of changed nodes
 	 */
@@ -871,7 +878,7 @@ public function fixTree($root = null)
 	}
 
 	/**
-	 * @param NodeTrait|Model $root
+	 * @param Model&Node $root
 	 *
 	 * @return int
 	 */
@@ -882,7 +889,7 @@ public function fixSubtree($root)
 
 	/**
 	 * @param array                $dictionary
-	 * @param NodeTrait|Model|null $parent
+	 * @param (Model&Node)|null $parent
 	 *
 	 * @return int
 	 */
@@ -935,7 +942,7 @@ protected static function reorderNodes(
 			return $cut;
 		}
 
-		/** @var Model|NodeTrait $model */
+		/** @var Model&Node $model */
 		foreach ($dictionary[$parentId] as $model) {
 			$lft = $cut;
 
@@ -983,7 +990,7 @@ public function rebuildTree(array $data, $delete = false, $root = null)
 
 		$this->buildRebuildDictionary($dictionary, $data, $existing, $parentId);
 
-		/** @var Model|NodeTrait $model */
+		/** @var Model&Node $model */
 		if (!empty($existing)) {
 			if ($delete && !$this->model->usesSoftDelete()) {
 				$this->model
@@ -1034,7 +1041,7 @@ protected function buildRebuildDictionary(array &$dictionary,
 		$keyName = $this->model->getKeyName();
 
 		foreach ($data as $itemData) {
-			/** @var NodeTrait|Model $model */
+			/** @var Model&Node $model */
 			if (!isset($itemData[$keyName])) {
 				$model = $this->model->newInstance($this->model->getAttributes());
 
@@ -1071,7 +1078,7 @@ protected function buildRebuildDictionary(array &$dictionary,
 	/**
 	 * @param string|null $table
 	 *
-	 * @return $this
+	 * @return QueryBuilder<Tmodelkey,Tmodel>
 	 */
 	public function applyNestedSetScope($table = null)
 	{
diff --git a/tests/models/Category.php b/tests/models/Category.php
index 241482e..c031f3d 100644
--- a/tests/models/Category.php
+++ b/tests/models/Category.php
@@ -1,11 +1,14 @@
 <?php
 
 use Illuminate\Database\Eloquent\Model;
+use \Illuminate\Database\Eloquent\SoftDeletes;
+use \Kalnoy\Nestedset\Node;
+use \Kalnoy\Nestedset\NodeTrait;
 
-class Category extends Model implements \Kalnoy\Nestedset\Node
+class Category extends Model implements Node
 {
-	use \Illuminate\Database\Eloquent\SoftDeletes;
-	use \Kalnoy\Nestedset\NodeTrait;
+	use SoftDeletes;
+	use NodeTrait;
 
 	protected $fillable = ['name', 'parent_id'];
 
diff --git a/tests/models/DuplicateCategory.php b/tests/models/DuplicateCategory.php
index c3b1e61..1fa8e19 100644
--- a/tests/models/DuplicateCategory.php
+++ b/tests/models/DuplicateCategory.php
@@ -1,10 +1,12 @@
 <?php
 
 use Illuminate\Database\Eloquent\Model;
+use \Kalnoy\Nestedset\Node;
+use \Kalnoy\Nestedset\NodeTrait;
 
-class DuplicateCategory extends Model implements \Kalnoy\Nestedset\Node
+class DuplicateCategory extends Model implements Node
 {
-	use \Kalnoy\Nestedset\NodeTrait;
+	use NodeTrait;
 
 	protected $table = 'categories';
 
diff --git a/tests/models/MenuItem.php b/tests/models/MenuItem.php
index 5dbb1b4..426b5a5 100644
--- a/tests/models/MenuItem.php
+++ b/tests/models/MenuItem.php
@@ -1,10 +1,12 @@
 <?php
 
 use Illuminate\Database\Eloquent\Model;
+use \Kalnoy\Nestedset\Node;
+use \Kalnoy\Nestedset\NodeTrait;
 
-class MenuItem extends Model implements \Kalnoy\Nestedset\Node
+class MenuItem extends Model implements Node
 {
-	use \Kalnoy\Nestedset\NodeTrait;
+	use NodeTrait;
 
 	public $timestamps = false;