diff --git a/lib/PhpParser/Builder/Declaration.php b/lib/PhpParser/Builder/Declaration.php
index df50cfb676..6d71657cb3 100644
--- a/lib/PhpParser/Builder/Declaration.php
+++ b/lib/PhpParser/Builder/Declaration.php
@@ -8,6 +8,13 @@
 abstract class Declaration implements PhpParser\Builder {
     protected $attributes = [];
 
+    /**
+     * Adds a statement.
+     *
+     * @param PhpParser\Node\Stmt|PhpParser\Builder $stmt The statement to add
+     *
+     * @return $this The builder instance (for fluid interface)
+     */
     abstract public function addStmt($stmt);
 
     /**
diff --git a/lib/PhpParser/Internal/DiffElem.php b/lib/PhpParser/Internal/DiffElem.php
index d10409f400..b25925d2d4 100644
--- a/lib/PhpParser/Internal/DiffElem.php
+++ b/lib/PhpParser/Internal/DiffElem.php
@@ -18,6 +18,11 @@ class DiffElem {
     /** @var mixed Is null for remove operations */
     public $new;
 
+    /**
+     * @param int $type One of the TYPE_* constants
+     * @param mixed $old Is null for add operations
+     * @param mixed $new Is null for remove operations
+     */
     public function __construct(int $type, $old, $new) {
         $this->type = $type;
         $this->old = $old;
diff --git a/lib/PhpParser/Internal/TokenStream.php b/lib/PhpParser/Internal/TokenStream.php
index 72a28dcae9..5dbd9912ad 100644
--- a/lib/PhpParser/Internal/TokenStream.php
+++ b/lib/PhpParser/Internal/TokenStream.php
@@ -102,6 +102,7 @@ public function haveTokenImmediatelyAfter(int $pos, $expectedTokenType): bool {
         return false;
     }
 
+    /** @param int|string|array $skipTokenType */
     public function skipLeft(int $pos, $skipTokenType) {
         $tokens = $this->tokens;
 
@@ -119,6 +120,7 @@ public function skipLeft(int $pos, $skipTokenType) {
         return $this->skipLeftWhitespace($pos);
     }
 
+    /** @param int|string|array $skipTokenType */
     public function skipRight(int $pos, $skipTokenType) {
         $tokens = $this->tokens;
 
@@ -168,6 +170,7 @@ public function skipRightWhitespace(int $pos): int {
         return $pos;
     }
 
+    /** @param int|string|array $findTokenType */
     public function findRight(int $pos, $findTokenType) {
         $tokens = $this->tokens;
         for ($count = \count($tokens); $pos < $count; $pos++) {
diff --git a/lib/PhpParser/JsonDecoder.php b/lib/PhpParser/JsonDecoder.php
index fa9d661977..d4965c7be0 100644
--- a/lib/PhpParser/JsonDecoder.php
+++ b/lib/PhpParser/JsonDecoder.php
@@ -15,6 +15,7 @@ public function decode(string $json) {
         return $this->decodeRecursive($value);
     }
 
+    /** @param mixed $value */
     private function decodeRecursive($value) {
         if (\is_array($value)) {
             if (isset($value['nodeType'])) {
diff --git a/lib/PhpParser/NameContext.php b/lib/PhpParser/NameContext.php
index 9aa50f438e..94afb4b8ad 100644
--- a/lib/PhpParser/NameContext.php
+++ b/lib/PhpParser/NameContext.php
@@ -226,7 +226,7 @@ public function getShortName(string $name, int $type): Name {
         return $shortestName;
     }
 
-    private function resolveAlias(Name $name, $type) {
+    private function resolveAlias(Name $name, int $type) {
         $firstPart = $name->getFirst();
 
         if ($name->isQualified()) {
diff --git a/lib/PhpParser/Node/Stmt/Class_.php b/lib/PhpParser/Node/Stmt/Class_.php
index 453cffe472..04ae6a1fea 100644
--- a/lib/PhpParser/Node/Stmt/Class_.php
+++ b/lib/PhpParser/Node/Stmt/Class_.php
@@ -92,7 +92,7 @@ public function isAnonymous(): bool {
     /**
      * @internal
      */
-    public static function verifyClassModifier($a, $b) {
+    public static function verifyClassModifier(int $a, int $b) {
         if ($a & Modifiers::ABSTRACT && $b & Modifiers::ABSTRACT) {
             throw new Error('Multiple abstract modifiers are not allowed');
         }
@@ -113,7 +113,7 @@ public static function verifyClassModifier($a, $b) {
     /**
      * @internal
      */
-    public static function verifyModifier($a, $b) {
+    public static function verifyModifier(int $a, int $b) {
         if ($a & Modifiers::VISIBILITY_MASK && $b & Modifiers::VISIBILITY_MASK) {
             throw new Error('Multiple access type modifiers are not allowed');
         }
diff --git a/lib/PhpParser/NodeDumper.php b/lib/PhpParser/NodeDumper.php
index 802f483986..78f8d76e94 100644
--- a/lib/PhpParser/NodeDumper.php
+++ b/lib/PhpParser/NodeDumper.php
@@ -43,6 +43,7 @@ public function dump($node, ?string $code = null): string {
         return $this->dumpRecursive($node);
     }
 
+    /** @param Node|Comment|array $node */
     protected function dumpRecursive($node) {
         if ($node instanceof Node) {
             $r = $node->getType();
@@ -107,7 +108,7 @@ protected function dumpRecursive($node) {
         return $r . "\n)";
     }
 
-    protected function dumpFlags($flags) {
+    protected function dumpFlags(int $flags) {
         $strs = [];
         if ($flags & Modifiers::PUBLIC) {
             $strs[] = 'PUBLIC';
@@ -138,7 +139,7 @@ protected function dumpFlags($flags) {
         }
     }
 
-    protected function dumpIncludeType($type) {
+    protected function dumpIncludeType(int $type) {
         $map = [
             Include_::TYPE_INCLUDE      => 'TYPE_INCLUDE',
             Include_::TYPE_INCLUDE_ONCE => 'TYPE_INCLUDE_ONCE',
@@ -152,7 +153,7 @@ protected function dumpIncludeType($type) {
         return $map[$type] . ' (' . $type . ')';
     }
 
-    protected function dumpUseType($type) {
+    protected function dumpUseType(int $type) {
         $map = [
             Use_::TYPE_UNKNOWN  => 'TYPE_UNKNOWN',
             Use_::TYPE_NORMAL   => 'TYPE_NORMAL',
@@ -190,7 +191,7 @@ protected function dumpPosition(Node $node): ?string {
     }
 
     // Copied from Error class
-    private function toColumn($code, $pos) {
+    private function toColumn(string $code, int $pos) {
         if ($pos > strlen($code)) {
             throw new \RuntimeException('Invalid position information');
         }
diff --git a/lib/PhpParser/NodeTraverser.php b/lib/PhpParser/NodeTraverser.php
index 0d81aedb37..427e59993a 100644
--- a/lib/PhpParser/NodeTraverser.php
+++ b/lib/PhpParser/NodeTraverser.php
@@ -272,7 +272,7 @@ protected function traverseArray(array $nodes): array {
         return $nodes;
     }
 
-    private function ensureReplacementReasonable($old, $new) {
+    private function ensureReplacementReasonable(Node $old, Node $new) {
         if ($old instanceof Node\Stmt && $new instanceof Node\Expr) {
             throw new \LogicException(
                 "Trying to replace statement ({$old->getType()}) " .
diff --git a/lib/PhpParser/NodeVisitor/NameResolver.php b/lib/PhpParser/NodeVisitor/NameResolver.php
index d00374bf43..e0352a0082 100644
--- a/lib/PhpParser/NodeVisitor/NameResolver.php
+++ b/lib/PhpParser/NodeVisitor/NameResolver.php
@@ -160,7 +160,7 @@ public function enterNode(Node $node) {
         return null;
     }
 
-    private function addAlias(Node\UseItem $use, $type, ?Name $prefix = null) {
+    private function addAlias(Node\UseItem $use, int $type, ?Name $prefix = null) {
         // Add prefix for group uses
         $name = $prefix ? Name::concat($prefix, $use->name) : $use->name;
         // Type is determined either by individual element or whole use declaration
@@ -180,7 +180,7 @@ private function resolveSignature($node) {
         $node->returnType = $this->resolveType($node->returnType);
     }
 
-    private function resolveType($node) {
+    private function resolveType(?Node $node) {
         if ($node instanceof Name) {
             return $this->resolveClassName($node);
         }
diff --git a/lib/PhpParser/ParserAbstract.php b/lib/PhpParser/ParserAbstract.php
index dccc5865f6..3686206759 100644
--- a/lib/PhpParser/ParserAbstract.php
+++ b/lib/PhpParser/ParserAbstract.php
@@ -11,6 +11,7 @@
 use PhpParser\Node\Expr;
 use PhpParser\Node\Expr\Array_;
 use PhpParser\Node\Expr\Cast\Double;
+use PhpParser\Node\Identifier;
 use PhpParser\Node\Name;
 use PhpParser\Node\Param;
 use PhpParser\Node\Scalar\InterpolatedString;
@@ -662,7 +663,7 @@ protected function getFloatCastKind(string $cast): int {
         return Double::KIND_DOUBLE;
     }
 
-    protected function parseLNumber($str, $attributes, $allowInvalidOctal = false) {
+    protected function parseLNumber(string $str, array $attributes, bool $allowInvalidOctal = false) {
         try {
             return Int_::fromString($str, $attributes, $allowInvalidOctal);
         } catch (Error $error) {
@@ -725,6 +726,7 @@ function ($matches) use ($indentLen, $indentChar, $attributes) {
         );
     }
 
+    /** @param string|array $contents */
     protected function parseDocString(
         string $startToken, $contents, string $endToken,
         array $attributes, array $endTokenAttributes, bool $parseUnicodeEscape
@@ -872,7 +874,7 @@ protected function postprocessList(Expr\List_ $node): void {
         }
     }
 
-    protected function checkClassModifier($a, $b, $modifierPos) {
+    protected function checkClassModifier(int $a, int $b, int $modifierPos) {
         try {
             Class_::verifyClassModifier($a, $b);
         } catch (Error $error) {
@@ -881,7 +883,7 @@ protected function checkClassModifier($a, $b, $modifierPos) {
         }
     }
 
-    protected function checkModifier($a, $b, $modifierPos) {
+    protected function checkModifier(int $a, int $b, int $modifierPos) {
         // Jumping through some hoops here because verifyModifier() is also used elsewhere
         try {
             Class_::verifyModifier($a, $b);
@@ -920,7 +922,7 @@ protected function checkNamespace(Namespace_ $node) {
         }
     }
 
-    private function checkClassName($name, $namePos) {
+    private function checkClassName(?Identifier $name, int $namePos) {
         if (null !== $name && $name->isSpecialClassName()) {
             $this->emitError(new Error(
                 sprintf('Cannot use \'%s\' as class name as it is reserved', $name),
@@ -940,7 +942,7 @@ private function checkImplementedInterfaces(array $interfaces) {
         }
     }
 
-    protected function checkClass(Class_ $node, $namePos) {
+    protected function checkClass(Class_ $node, int $namePos) {
         $this->checkClassName($node->name, $namePos);
 
         if ($node->extends && $node->extends->isSpecialClassName()) {
@@ -953,17 +955,17 @@ protected function checkClass(Class_ $node, $namePos) {
         $this->checkImplementedInterfaces($node->implements);
     }
 
-    protected function checkInterface(Interface_ $node, $namePos) {
+    protected function checkInterface(Interface_ $node, int $namePos) {
         $this->checkClassName($node->name, $namePos);
         $this->checkImplementedInterfaces($node->extends);
     }
 
-    protected function checkEnum(Enum_ $node, $namePos) {
+    protected function checkEnum(Enum_ $node, int $namePos) {
         $this->checkClassName($node->name, $namePos);
         $this->checkImplementedInterfaces($node->implements);
     }
 
-    protected function checkClassMethod(ClassMethod $node, $modifierPos) {
+    protected function checkClassMethod(ClassMethod $node, int $modifierPos) {
         if ($node->flags & Modifiers::STATIC) {
             switch ($node->name->toLowerString()) {
                 case '__construct':
@@ -991,7 +993,7 @@ protected function checkClassMethod(ClassMethod $node, $modifierPos) {
         }
     }
 
-    protected function checkClassConst(ClassConst $node, $modifierPos) {
+    protected function checkClassConst(ClassConst $node, int $modifierPos) {
         if ($node->flags & Modifiers::STATIC) {
             $this->emitError(new Error(
                 "Cannot use 'static' as constant modifier",
@@ -1009,7 +1011,7 @@ protected function checkClassConst(ClassConst $node, $modifierPos) {
         }
     }
 
-    protected function checkProperty(Property $node, $modifierPos) {
+    protected function checkProperty(Property $node, int $modifierPos) {
         if ($node->flags & Modifiers::ABSTRACT) {
             $this->emitError(new Error('Properties cannot be declared abstract',
                 $this->getAttributesAt($modifierPos)));
@@ -1021,7 +1023,7 @@ protected function checkProperty(Property $node, $modifierPos) {
         }
     }
 
-    protected function checkUseUse(UseItem $node, $namePos) {
+    protected function checkUseUse(UseItem $node, int $namePos) {
         if ($node->alias && $node->alias->isSpecialClassName()) {
             $this->emitError(new Error(
                 sprintf(
diff --git a/lib/PhpParser/PrettyPrinter/Standard.php b/lib/PhpParser/PrettyPrinter/Standard.php
index be4ddcf113..6241aec6a9 100644
--- a/lib/PhpParser/PrettyPrinter/Standard.php
+++ b/lib/PhpParser/PrettyPrinter/Standard.php
@@ -736,7 +736,7 @@ protected function pUseItem(Node\UseItem $node) {
              . (null !== $node->alias ? ' as ' . $node->alias : '');
     }
 
-    protected function pUseType($type) {
+    protected function pUseType(int $type) {
         return $type === Stmt\Use_::TYPE_FUNCTION ? 'function '
             : ($type === Stmt\Use_::TYPE_CONSTANT ? 'const ' : '');
     }
@@ -978,7 +978,7 @@ protected function pStmt_Nop(Stmt\Nop $node) {
 
     // Helpers
 
-    protected function pClassCommon(Stmt\Class_ $node, $afterClassToken) {
+    protected function pClassCommon(Stmt\Class_ $node, string $afterClassToken) {
         return $this->pAttrGroups($node->attrGroups, $node->name === null)
             . $this->pModifiers($node->flags)
             . 'class' . $afterClassToken
@@ -987,7 +987,7 @@ protected function pClassCommon(Stmt\Class_ $node, $afterClassToken) {
             . $this->nl . '{' . $this->pStmts($node->stmts) . $this->nl . '}';
     }
 
-    protected function pObjectProperty($node) {
+    protected function pObjectProperty(Node $node) {
         if ($node instanceof Expr) {
             return '{' . $this->p($node) . '}';
         } else {
@@ -995,7 +995,7 @@ protected function pObjectProperty($node) {
         }
     }
 
-    protected function pEncapsList(array $encapsList, $quote) {
+    protected function pEncapsList(array $encapsList, ?string $quote) {
         $return = '';
         foreach ($encapsList as $element) {
             if ($element instanceof Node\InterpolatedStringPart) {
@@ -1017,7 +1017,7 @@ protected function pSingleQuotedString(string $string) {
         return '\'' . preg_replace($regex, '\\\\$0', $string) . '\'';
     }
 
-    protected function escapeString($string, $quote) {
+    protected function escapeString(string $string, ?string $quote) {
         if (null === $quote) {
             // For doc strings, don't escape newlines
             $escaped = addcslashes($string, "\t\f\v$\\");
@@ -1050,14 +1050,14 @@ protected function escapeString($string, $quote) {
         }, $escaped);
     }
 
-    protected function containsEndLabel($string, $label, $atStart = true, $atEnd = true) {
+    protected function containsEndLabel(string $string, string $label, bool $atStart = true, bool $atEnd = true) {
         $start = $atStart ? '(?:^|[\r\n])' : '[\r\n]';
         $end = $atEnd ? '(?:$|[;\r\n])' : '[;\r\n]';
         return false !== strpos($string, $label)
             && preg_match('/' . $start . $label . $end . '/', $string);
     }
 
-    protected function encapsedContainsEndLabel(array $parts, $label) {
+    protected function encapsedContainsEndLabel(array $parts, string $label) {
         foreach ($parts as $i => $part) {
             $atStart = $i === 0;
             $atEnd = $i === count($parts) - 1;