diff --git a/src/Query/Mysql/Acos.php b/src/Query/Mysql/Acos.php
index 8ffc6ae8..4e2f71b6 100644
--- a/src/Query/Mysql/Acos.php
+++ b/src/Query/Mysql/Acos.php
@@ -9,14 +9,14 @@ class Acos extends FunctionNode
 {
     public $arithmeticExpression;
 
-    public function getSql(\Doctrine\ORM\Query\SqlWalker $sqlWalker)
+    public function getSql(\Doctrine\ORM\Query\SqlWalker $sqlWalker): string
     {
         return 'ACOS(' . $sqlWalker->walkSimpleArithmeticExpression(
             $this->arithmeticExpression
         ) . ')';
     }
 
-    public function parse(\Doctrine\ORM\Query\Parser $parser)
+    public function parse(\Doctrine\ORM\Query\Parser $parser): void
     {
         $parser->match(Lexer::T_IDENTIFIER);
         $parser->match(Lexer::T_OPEN_PARENTHESIS);
diff --git a/src/Query/Mysql/AddTime.php b/src/Query/Mysql/AddTime.php
index c0fb6aee..30a16cb0 100644
--- a/src/Query/Mysql/AddTime.php
+++ b/src/Query/Mysql/AddTime.php
@@ -14,12 +14,12 @@ class AddTime extends FunctionNode
 
     public $time;
 
-    public function getSql(\Doctrine\ORM\Query\SqlWalker $sqlWalker)
+    public function getSql(\Doctrine\ORM\Query\SqlWalker $sqlWalker): string
     {
         return 'ADDTIME(' . $sqlWalker->walkArithmeticPrimary($this->date) . ', ' . $sqlWalker->walkArithmeticPrimary($this->time) . ')';
     }
 
-    public function parse(\Doctrine\ORM\Query\Parser $parser)
+    public function parse(\Doctrine\ORM\Query\Parser $parser): void
     {
         $parser->match(Lexer::T_IDENTIFIER);
         $parser->match(Lexer::T_OPEN_PARENTHESIS);
diff --git a/src/Query/Mysql/AesDecrypt.php b/src/Query/Mysql/AesDecrypt.php
index 056c8de9..0c52242e 100644
--- a/src/Query/Mysql/AesDecrypt.php
+++ b/src/Query/Mysql/AesDecrypt.php
@@ -11,7 +11,7 @@ class AesDecrypt extends FunctionNode
 
     public $key = '';
 
-    public function parse(\Doctrine\ORM\Query\Parser $parser)
+    public function parse(\Doctrine\ORM\Query\Parser $parser): void
     {
         $parser->match(Lexer::T_IDENTIFIER);
         $parser->match(Lexer::T_OPEN_PARENTHESIS);
@@ -21,7 +21,7 @@ public function parse(\Doctrine\ORM\Query\Parser $parser)
         $parser->match(Lexer::T_CLOSE_PARENTHESIS);
     }
 
-    public function getSql(\Doctrine\ORM\Query\SqlWalker $sqlWalker)
+    public function getSql(\Doctrine\ORM\Query\SqlWalker $sqlWalker): string
     {
         return sprintf(
             'AES_DECRYPT(%s, %s)',
diff --git a/src/Query/Mysql/AesEncrypt.php b/src/Query/Mysql/AesEncrypt.php
index 779f5e36..804a627d 100644
--- a/src/Query/Mysql/AesEncrypt.php
+++ b/src/Query/Mysql/AesEncrypt.php
@@ -11,7 +11,7 @@ class AesEncrypt extends FunctionNode
 
     public $key = '';
 
-    public function parse(\Doctrine\ORM\Query\Parser $parser)
+    public function parse(\Doctrine\ORM\Query\Parser $parser): void
     {
         $parser->match(Lexer::T_IDENTIFIER);
         $parser->match(Lexer::T_OPEN_PARENTHESIS);
@@ -21,7 +21,7 @@ public function parse(\Doctrine\ORM\Query\Parser $parser)
         $parser->match(Lexer::T_CLOSE_PARENTHESIS);
     }
 
-    public function getSql(\Doctrine\ORM\Query\SqlWalker $sqlWalker)
+    public function getSql(\Doctrine\ORM\Query\SqlWalker $sqlWalker): string
     {
         return sprintf(
             'AES_ENCRYPT(%s, %s)',
diff --git a/src/Query/Mysql/AnyValue.php b/src/Query/Mysql/AnyValue.php
index b94fdd40..c7db908f 100644
--- a/src/Query/Mysql/AnyValue.php
+++ b/src/Query/Mysql/AnyValue.php
@@ -9,7 +9,7 @@ class AnyValue extends FunctionNode
 {
     public $value;
 
-    public function parse(\Doctrine\ORM\Query\Parser $parser)
+    public function parse(\Doctrine\ORM\Query\Parser $parser): void
     {
         $parser->match(Lexer::T_IDENTIFIER);
         $parser->match(Lexer::T_OPEN_PARENTHESIS);
@@ -17,7 +17,7 @@ public function parse(\Doctrine\ORM\Query\Parser $parser)
         $parser->match(Lexer::T_CLOSE_PARENTHESIS);
     }
 
-    public function getSql(\Doctrine\ORM\Query\SqlWalker $sqlWalker)
+    public function getSql(\Doctrine\ORM\Query\SqlWalker $sqlWalker): string
     {
         return sprintf(
             'ANY_VALUE(%s)',
diff --git a/src/Query/Mysql/Ascii.php b/src/Query/Mysql/Ascii.php
index b3450a32..28893478 100644
--- a/src/Query/Mysql/Ascii.php
+++ b/src/Query/Mysql/Ascii.php
@@ -9,12 +9,12 @@ class Ascii extends FunctionNode
 {
     private $string;
 
-    public function getSql(\Doctrine\ORM\Query\SqlWalker $sqlWalker)
+    public function getSql(\Doctrine\ORM\Query\SqlWalker $sqlWalker): string
     {
         return 'ASCII('.$sqlWalker->walkArithmeticPrimary($this->string).')';
     }
 
-    public function parse(\Doctrine\ORM\Query\Parser $parser)
+    public function parse(\Doctrine\ORM\Query\Parser $parser): void
     {
         $parser->match(Lexer::T_IDENTIFIER);
         $parser->match(Lexer::T_OPEN_PARENTHESIS);
diff --git a/src/Query/Mysql/Asin.php b/src/Query/Mysql/Asin.php
index a398c86c..c2d29684 100644
--- a/src/Query/Mysql/Asin.php
+++ b/src/Query/Mysql/Asin.php
@@ -9,14 +9,14 @@ class Asin extends FunctionNode
 {
     public $arithmeticExpression;
 
-    public function getSql(\Doctrine\ORM\Query\SqlWalker $sqlWalker)
+    public function getSql(\Doctrine\ORM\Query\SqlWalker $sqlWalker): string
     {
         return 'ASIN(' . $sqlWalker->walkSimpleArithmeticExpression(
             $this->arithmeticExpression
         ) . ')';
     }
 
-    public function parse(\Doctrine\ORM\Query\Parser $parser)
+    public function parse(\Doctrine\ORM\Query\Parser $parser): void
     {
         $parser->match(Lexer::T_IDENTIFIER);
         $parser->match(Lexer::T_OPEN_PARENTHESIS);
diff --git a/src/Query/Mysql/Atan.php b/src/Query/Mysql/Atan.php
index 64fe1b32..866e3737 100644
--- a/src/Query/Mysql/Atan.php
+++ b/src/Query/Mysql/Atan.php
@@ -12,7 +12,7 @@ class Atan extends FunctionNode
 
     public $optionalSecondExpression;
 
-    public function getSql(\Doctrine\ORM\Query\SqlWalker $sqlWalker)
+    public function getSql(\Doctrine\ORM\Query\SqlWalker $sqlWalker): string
     {
         $secondArgument = '';
 
@@ -28,7 +28,7 @@ public function getSql(\Doctrine\ORM\Query\SqlWalker $sqlWalker)
         . ')';
     }
 
-    public function parse(\Doctrine\ORM\Query\Parser $parser)
+    public function parse(\Doctrine\ORM\Query\Parser $parser): void
     {
         $parser->match(Lexer::T_IDENTIFIER);
         $parser->match(Lexer::T_OPEN_PARENTHESIS);
diff --git a/src/Query/Mysql/Atan2.php b/src/Query/Mysql/Atan2.php
index 9b934b23..70b2de98 100644
--- a/src/Query/Mysql/Atan2.php
+++ b/src/Query/Mysql/Atan2.php
@@ -11,7 +11,7 @@ class Atan2 extends FunctionNode
 
     public $secondExpression;
 
-    public function getSql(\Doctrine\ORM\Query\SqlWalker $sqlWalker)
+    public function getSql(\Doctrine\ORM\Query\SqlWalker $sqlWalker): string
     {
         $firstArgument = $sqlWalker->walkSimpleArithmeticExpression(
             $this->firstExpression
@@ -24,7 +24,7 @@ public function getSql(\Doctrine\ORM\Query\SqlWalker $sqlWalker)
         return 'ATAN2(' . $firstArgument . ', ' . $secondArgument . ')';
     }
 
-    public function parse(\Doctrine\ORM\Query\Parser $parser)
+    public function parse(\Doctrine\ORM\Query\Parser $parser): void
     {
         $parser->match(Lexer::T_IDENTIFIER);
         $parser->match(Lexer::T_OPEN_PARENTHESIS);
diff --git a/src/Query/Mysql/Binary.php b/src/Query/Mysql/Binary.php
index 56645e90..23bdfc47 100644
--- a/src/Query/Mysql/Binary.php
+++ b/src/Query/Mysql/Binary.php
@@ -12,7 +12,7 @@ class Binary extends FunctionNode
 {
     private $stringPrimary;
 
-    public function parse(\Doctrine\ORM\Query\Parser $parser)
+    public function parse(\Doctrine\ORM\Query\Parser $parser): void
     {
         $parser->match(Lexer::T_IDENTIFIER);
         $parser->match(Lexer::T_OPEN_PARENTHESIS);
@@ -22,7 +22,7 @@ public function parse(\Doctrine\ORM\Query\Parser $parser)
         $parser->match(Lexer::T_CLOSE_PARENTHESIS);
     }
 
-    public function getSql(\Doctrine\ORM\Query\SqlWalker $sqlWalker)
+    public function getSql(\Doctrine\ORM\Query\SqlWalker $sqlWalker): string
     {
         return 'BINARY('.$sqlWalker->walkSimpleArithmeticExpression($this->stringPrimary).')';
     }
diff --git a/src/Query/Mysql/BitCount.php b/src/Query/Mysql/BitCount.php
index 03b09706..9042b810 100644
--- a/src/Query/Mysql/BitCount.php
+++ b/src/Query/Mysql/BitCount.php
@@ -9,7 +9,7 @@ class BitCount extends FunctionNode
 {
     public $arithmeticExpression;
 
-    public function getSql(\Doctrine\ORM\Query\SqlWalker $sqlWalker)
+    public function getSql(\Doctrine\ORM\Query\SqlWalker $sqlWalker): string
     {
         return 'BIT_COUNT(' . $sqlWalker->walkSimpleArithmeticExpression(
             $this->arithmeticExpression
@@ -17,7 +17,7 @@ public function getSql(\Doctrine\ORM\Query\SqlWalker $sqlWalker)
         . ')';
     }
 
-    public function parse(\Doctrine\ORM\Query\Parser $parser)
+    public function parse(\Doctrine\ORM\Query\Parser $parser): void
     {
         $parser->match(Lexer::T_IDENTIFIER);
         $parser->match(Lexer::T_OPEN_PARENTHESIS);
diff --git a/src/Query/Mysql/BitXor.php b/src/Query/Mysql/BitXor.php
index cd3621be..211b5e32 100644
--- a/src/Query/Mysql/BitXor.php
+++ b/src/Query/Mysql/BitXor.php
@@ -14,14 +14,14 @@ class BitXor extends FunctionNode
 
     public $secondArithmetic;
 
-    public function getSql(\Doctrine\ORM\Query\SqlWalker $sqlWalker)
+    public function getSql(\Doctrine\ORM\Query\SqlWalker $sqlWalker): string
     {
         return $this->firstArithmetic->dispatch($sqlWalker)
             . ' ^ '
             . $this->secondArithmetic->dispatch($sqlWalker);
     }
 
-    public function parse(\Doctrine\ORM\Query\Parser $parser)
+    public function parse(\Doctrine\ORM\Query\Parser $parser): void
     {
         $parser->match(Lexer::T_IDENTIFIER);
         $parser->match(Lexer::T_OPEN_PARENTHESIS);
diff --git a/src/Query/Mysql/Cast.php b/src/Query/Mysql/Cast.php
index 57986323..5f44b7df 100644
--- a/src/Query/Mysql/Cast.php
+++ b/src/Query/Mysql/Cast.php
@@ -30,7 +30,7 @@ class Cast extends FunctionNode
      *
      * @throws QueryException
      */
-    public function parse(Parser $parser)
+    public function parse(Parser $parser): void
     {
         $parser->match(Lexer::T_IDENTIFIER);
         $parser->match(Lexer::T_OPEN_PARENTHESIS);
@@ -70,7 +70,7 @@ public function parse(Parser $parser)
      *
      * @return string
      */
-    public function getSql(SqlWalker $sqlWalker)
+    public function getSql(SqlWalker $sqlWalker): string
     {
         return sprintf(
             'CAST(%s AS %s)',
diff --git a/src/Query/Mysql/Ceil.php b/src/Query/Mysql/Ceil.php
index 5bfb1dbc..a7cf1cf8 100644
--- a/src/Query/Mysql/Ceil.php
+++ b/src/Query/Mysql/Ceil.php
@@ -9,12 +9,12 @@ class Ceil extends FunctionNode
 {
     private $arithmeticExpression;
 
-    public function getSql(\Doctrine\ORM\Query\SqlWalker $sqlWalker)
+    public function getSql(\Doctrine\ORM\Query\SqlWalker $sqlWalker): string
     {
         return 'CEIL(' . $sqlWalker->walkSimpleArithmeticExpression($this->arithmeticExpression) . ')';
     }
 
-    public function parse(\Doctrine\ORM\Query\Parser $parser)
+    public function parse(\Doctrine\ORM\Query\Parser $parser): void
     {
         $parser->match(Lexer::T_IDENTIFIER);
         $parser->match(Lexer::T_OPEN_PARENTHESIS);
diff --git a/src/Query/Mysql/CharLength.php b/src/Query/Mysql/CharLength.php
index 422b600f..cdc3c0a8 100644
--- a/src/Query/Mysql/CharLength.php
+++ b/src/Query/Mysql/CharLength.php
@@ -12,12 +12,12 @@ class CharLength extends FunctionNode
 {
     private $expr;
 
-    public function getSql(\Doctrine\ORM\Query\SqlWalker $sqlWalker)
+    public function getSql(\Doctrine\ORM\Query\SqlWalker $sqlWalker): string
     {
         return 'CHAR_LENGTH('.$sqlWalker->walkArithmeticPrimary($this->expr1).')';
     }
 
-    public function parse(\Doctrine\ORM\Query\Parser $parser)
+    public function parse(\Doctrine\ORM\Query\Parser $parser): void
     {
         $parser->match(Lexer::T_IDENTIFIER);
         $parser->match(Lexer::T_OPEN_PARENTHESIS);
diff --git a/src/Query/Mysql/Collate.php b/src/Query/Mysql/Collate.php
index f6aa4236..311e1a7b 100644
--- a/src/Query/Mysql/Collate.php
+++ b/src/Query/Mysql/Collate.php
@@ -24,7 +24,7 @@ class Collate extends FunctionNode
     /**
      * @param \Doctrine\ORM\Query\Parser $parser
      */
-    public function parse(\Doctrine\ORM\Query\Parser $parser)
+    public function parse(\Doctrine\ORM\Query\Parser $parser): void
     {
         $parser->match(Lexer::T_IDENTIFIER);
         $parser->match(Lexer::T_OPEN_PARENTHESIS);
@@ -45,7 +45,7 @@ public function parse(\Doctrine\ORM\Query\Parser $parser)
      * @param \Doctrine\ORM\Query\SqlWalker $sqlWalker
      * @return string
      */
-    public function getSql(\Doctrine\ORM\Query\SqlWalker $sqlWalker)
+    public function getSql(\Doctrine\ORM\Query\SqlWalker $sqlWalker): string
     {
         return sprintf('%s COLLATE %s', $sqlWalker->walkStringPrimary($this->stringPrimary), $this->collation);
     }
diff --git a/src/Query/Mysql/ConcatWs.php b/src/Query/Mysql/ConcatWs.php
index 1b268d6a..68a8a6d3 100644
--- a/src/Query/Mysql/ConcatWs.php
+++ b/src/Query/Mysql/ConcatWs.php
@@ -14,7 +14,7 @@ class ConcatWs extends FunctionNode
 
     private $notEmpty = false;
 
-    public function parse(\Doctrine\ORM\Query\Parser $parser)
+    public function parse(\Doctrine\ORM\Query\Parser $parser): void
     {
         $parser->match(Lexer::T_IDENTIFIER);
         $parser->match(Lexer::T_OPEN_PARENTHESIS);
@@ -53,7 +53,7 @@ public function parse(\Doctrine\ORM\Query\Parser $parser)
         $parser->match(Lexer::T_CLOSE_PARENTHESIS);
     }
 
-    public function getSql(\Doctrine\ORM\Query\SqlWalker $sqlWalker)
+    public function getSql(\Doctrine\ORM\Query\SqlWalker $sqlWalker): string
     {
         // Create an array to hold the query elements.
         $queryBuilder = ['CONCAT_WS('];
diff --git a/src/Query/Mysql/ConvertTz.php b/src/Query/Mysql/ConvertTz.php
index 0c302ddd..732505eb 100644
--- a/src/Query/Mysql/ConvertTz.php
+++ b/src/Query/Mysql/ConvertTz.php
@@ -21,7 +21,7 @@ class ConvertTz extends FunctionNode
     /**
      * @inheritdoc
      */
-    public function getSql(SqlWalker $sqlWalker)
+    public function getSql(SqlWalker $sqlWalker): string
     {
         return sprintf(
             'CONVERT_TZ(%s, %s, %s)',
@@ -34,7 +34,7 @@ public function getSql(SqlWalker $sqlWalker)
     /**
      * @inheritdoc
      */
-    public function parse(Parser $parser)
+    public function parse(Parser $parser): void
     {
         $parser->match(Lexer::T_IDENTIFIER);
         $parser->match(Lexer::T_OPEN_PARENTHESIS);
diff --git a/src/Query/Mysql/Cos.php b/src/Query/Mysql/Cos.php
index c6577192..47ef44c9 100644
--- a/src/Query/Mysql/Cos.php
+++ b/src/Query/Mysql/Cos.php
@@ -9,14 +9,14 @@ class Cos extends FunctionNode
 {
     public $arithmeticExpression;
 
-    public function getSql(\Doctrine\ORM\Query\SqlWalker $sqlWalker)
+    public function getSql(\Doctrine\ORM\Query\SqlWalker $sqlWalker): string
     {
         return 'COS(' . $sqlWalker->walkSimpleArithmeticExpression(
             $this->arithmeticExpression
         ) . ')';
     }
 
-    public function parse(\Doctrine\ORM\Query\Parser $parser)
+    public function parse(\Doctrine\ORM\Query\Parser $parser): void
     {
         $parser->match(Lexer::T_IDENTIFIER);
         $parser->match(Lexer::T_OPEN_PARENTHESIS);
diff --git a/src/Query/Mysql/Cot.php b/src/Query/Mysql/Cot.php
index 1bb48340..cf597205 100644
--- a/src/Query/Mysql/Cot.php
+++ b/src/Query/Mysql/Cot.php
@@ -9,14 +9,14 @@ class Cot extends FunctionNode
 {
     public $arithmeticExpression;
 
-    public function getSql(\Doctrine\ORM\Query\SqlWalker $sqlWalker)
+    public function getSql(\Doctrine\ORM\Query\SqlWalker $sqlWalker): string
     {
         return 'COT(' . $sqlWalker->walkSimpleArithmeticExpression(
             $this->arithmeticExpression
         ) . ')';
     }
 
-    public function parse(\Doctrine\ORM\Query\Parser $parser)
+    public function parse(\Doctrine\ORM\Query\Parser $parser): void
     {
         $parser->match(Lexer::T_IDENTIFIER);
         $parser->match(Lexer::T_OPEN_PARENTHESIS);
diff --git a/src/Query/Mysql/CountIf.php b/src/Query/Mysql/CountIf.php
index 599d7516..694b7006 100644
--- a/src/Query/Mysql/CountIf.php
+++ b/src/Query/Mysql/CountIf.php
@@ -16,7 +16,7 @@ class CountIf extends FunctionNode
 
     private $inverse = false;
 
-    public function parse(\Doctrine\ORM\Query\Parser $parser)
+    public function parse(\Doctrine\ORM\Query\Parser $parser): void
     {
         $parser->match(Lexer::T_IDENTIFIER);
         $parser->match(Lexer::T_OPEN_PARENTHESIS);
@@ -43,7 +43,7 @@ public function parse(\Doctrine\ORM\Query\Parser $parser)
         $parser->match(Lexer::T_CLOSE_PARENTHESIS);
     }
 
-    public function getSql(\Doctrine\ORM\Query\SqlWalker $sqlWalker)
+    public function getSql(\Doctrine\ORM\Query\SqlWalker $sqlWalker): string
     {
         return sprintf(
             'COUNT(CASE %s WHEN %s THEN %s END)',
diff --git a/src/Query/Mysql/Crc32.php b/src/Query/Mysql/Crc32.php
index c1a7c01b..9172c06e 100644
--- a/src/Query/Mysql/Crc32.php
+++ b/src/Query/Mysql/Crc32.php
@@ -12,14 +12,14 @@ class Crc32 extends FunctionNode
 {
     public $stringPrimary;
 
-    public function getSql(\Doctrine\ORM\Query\SqlWalker $sqlWalker)
+    public function getSql(\Doctrine\ORM\Query\SqlWalker $sqlWalker): string
     {
         return 'CRC32(' .
             $sqlWalker->walkStringPrimary($this->stringPrimary) .
         ')';
     }
 
-    public function parse(\Doctrine\ORM\Query\Parser $parser)
+    public function parse(\Doctrine\ORM\Query\Parser $parser): void
     {
         $parser->match(Lexer::T_IDENTIFIER);
         $parser->match(Lexer::T_OPEN_PARENTHESIS);
diff --git a/src/Query/Mysql/Date.php b/src/Query/Mysql/Date.php
index cfb042f4..d65deee9 100644
--- a/src/Query/Mysql/Date.php
+++ b/src/Query/Mysql/Date.php
@@ -12,12 +12,12 @@ class Date extends FunctionNode
 {
     public $date;
 
-    public function getSql(\Doctrine\ORM\Query\SqlWalker $sqlWalker)
+    public function getSql(\Doctrine\ORM\Query\SqlWalker $sqlWalker): string
     {
         return 'DATE(' . $sqlWalker->walkArithmeticPrimary($this->date) . ')';
     }
 
-    public function parse(\Doctrine\ORM\Query\Parser $parser)
+    public function parse(\Doctrine\ORM\Query\Parser $parser): void
     {
         $parser->match(Lexer::T_IDENTIFIER);
         $parser->match(Lexer::T_OPEN_PARENTHESIS);
diff --git a/src/Query/Mysql/DateAdd.php b/src/Query/Mysql/DateAdd.php
index 2c50d99e..6280e9f9 100644
--- a/src/Query/Mysql/DateAdd.php
+++ b/src/Query/Mysql/DateAdd.php
@@ -37,7 +37,7 @@ class DateAdd extends FunctionNode
         'YEAR_MONTH',
     ];
 
-    public function parse(\Doctrine\ORM\Query\Parser $parser)
+    public function parse(\Doctrine\ORM\Query\Parser $parser): void
     {
         $parser->match(Lexer::T_IDENTIFIER);
         $parser->match(Lexer::T_OPEN_PARENTHESIS);
@@ -53,7 +53,7 @@ public function parse(\Doctrine\ORM\Query\Parser $parser)
         $parser->match(Lexer::T_CLOSE_PARENTHESIS);
     }
 
-    public function getSql(\Doctrine\ORM\Query\SqlWalker $sqlWalker)
+    public function getSql(\Doctrine\ORM\Query\SqlWalker $sqlWalker): string
     {
         $unit = strtoupper(is_string($this->unit) ? $this->unit : $this->unit->value);
 
diff --git a/src/Query/Mysql/DateDiff.php b/src/Query/Mysql/DateDiff.php
index a0952094..d66ca8a7 100644
--- a/src/Query/Mysql/DateDiff.php
+++ b/src/Query/Mysql/DateDiff.php
@@ -11,7 +11,7 @@ class DateDiff extends FunctionNode
 
     public $secondDateExpression = null;
 
-    public function parse(\Doctrine\ORM\Query\Parser $parser)
+    public function parse(\Doctrine\ORM\Query\Parser $parser): void
     {
         $parser->match(Lexer::T_IDENTIFIER);
         $parser->match(Lexer::T_OPEN_PARENTHESIS);
@@ -21,7 +21,7 @@ public function parse(\Doctrine\ORM\Query\Parser $parser)
         $parser->match(Lexer::T_CLOSE_PARENTHESIS);
     }
 
-    public function getSql(\Doctrine\ORM\Query\SqlWalker $sqlWalker)
+    public function getSql(\Doctrine\ORM\Query\SqlWalker $sqlWalker): string
     {
         return 'DATEDIFF(' .
             $sqlWalker->walkArithmeticTerm($this->firstDateExpression) . ', ' .
diff --git a/src/Query/Mysql/DateFormat.php b/src/Query/Mysql/DateFormat.php
index bd7a7e74..28770a6e 100644
--- a/src/Query/Mysql/DateFormat.php
+++ b/src/Query/Mysql/DateFormat.php
@@ -14,7 +14,7 @@ class DateFormat extends FunctionNode
 
     public $patternExpression = null;
 
-    public function parse(\Doctrine\ORM\Query\Parser $parser)
+    public function parse(\Doctrine\ORM\Query\Parser $parser): void
     {
         $parser->match(Lexer::T_IDENTIFIER);
         $parser->match(Lexer::T_OPEN_PARENTHESIS);
@@ -24,7 +24,7 @@ public function parse(\Doctrine\ORM\Query\Parser $parser)
         $parser->match(Lexer::T_CLOSE_PARENTHESIS);
     }
 
-    public function getSql(\Doctrine\ORM\Query\SqlWalker $sqlWalker)
+    public function getSql(\Doctrine\ORM\Query\SqlWalker $sqlWalker): string
     {
         return 'DATE_FORMAT(' .
             $this->dateExpression->dispatch($sqlWalker) . ', ' .
diff --git a/src/Query/Mysql/DateSub.php b/src/Query/Mysql/DateSub.php
index b1c94d79..5f66e7fa 100644
--- a/src/Query/Mysql/DateSub.php
+++ b/src/Query/Mysql/DateSub.php
@@ -14,7 +14,7 @@ class DateSub extends DateAdd
      * @throws QueryException
      * @return string
      */
-    public function getSql(\Doctrine\ORM\Query\SqlWalker $sqlWalker)
+    public function getSql(\Doctrine\ORM\Query\SqlWalker $sqlWalker): string
     {
         $unit = strtoupper(is_string($this->unit) ? $this->unit : $this->unit->value);
 
diff --git a/src/Query/Mysql/Day.php b/src/Query/Mysql/Day.php
index 49b2b0c3..36954cb9 100644
--- a/src/Query/Mysql/Day.php
+++ b/src/Query/Mysql/Day.php
@@ -13,12 +13,12 @@ class Day extends FunctionNode
 {
     public $date;
 
-    public function getSql(\Doctrine\ORM\Query\SqlWalker $sqlWalker)
+    public function getSql(\Doctrine\ORM\Query\SqlWalker $sqlWalker): string
     {
         return 'DAY(' . $sqlWalker->walkArithmeticPrimary($this->date) . ')';
     }
 
-    public function parse(\Doctrine\ORM\Query\Parser $parser)
+    public function parse(\Doctrine\ORM\Query\Parser $parser): void
     {
         $parser->match(Lexer::T_IDENTIFIER);
         $parser->match(Lexer::T_OPEN_PARENTHESIS);
diff --git a/src/Query/Mysql/DayName.php b/src/Query/Mysql/DayName.php
index 59552c46..70c14352 100644
--- a/src/Query/Mysql/DayName.php
+++ b/src/Query/Mysql/DayName.php
@@ -12,12 +12,12 @@ class DayName extends FunctionNode
 {
     public $date;
 
-    public function getSql(\Doctrine\ORM\Query\SqlWalker $sqlWalker)
+    public function getSql(\Doctrine\ORM\Query\SqlWalker $sqlWalker): string
     {
         return 'DAYNAME(' . $sqlWalker->walkArithmeticPrimary($this->date) . ')';
     }
 
-    public function parse(\Doctrine\ORM\Query\Parser $parser)
+    public function parse(\Doctrine\ORM\Query\Parser $parser): void
     {
         $parser->match(Lexer::T_IDENTIFIER);
         $parser->match(Lexer::T_OPEN_PARENTHESIS);
diff --git a/src/Query/Mysql/DayOfWeek.php b/src/Query/Mysql/DayOfWeek.php
index 6bb91d1a..68cf981f 100644
--- a/src/Query/Mysql/DayOfWeek.php
+++ b/src/Query/Mysql/DayOfWeek.php
@@ -8,19 +8,19 @@
 class DayOfWeek extends FunctionNode
 {
     public $date;
-    
-    public function getSql(\Doctrine\ORM\Query\SqlWalker $sqlWalker)
+
+    public function getSql(\Doctrine\ORM\Query\SqlWalker $sqlWalker): string
     {
         return 'DAYOFWEEK(' . $sqlWalker->walkArithmeticPrimary($this->date) . ')';
     }
-    
-    public function parse(\Doctrine\ORM\Query\Parser $parser)
+
+    public function parse(\Doctrine\ORM\Query\Parser $parser): void
     {
         $parser->match(Lexer::T_IDENTIFIER);
         $parser->match(Lexer::T_OPEN_PARENTHESIS);
-        
+
         $this->date = $parser->ArithmeticPrimary();
-        
+
         $parser->match(Lexer::T_CLOSE_PARENTHESIS);
     }
 }
diff --git a/src/Query/Mysql/DayOfYear.php b/src/Query/Mysql/DayOfYear.php
index a836db31..7285d982 100644
--- a/src/Query/Mysql/DayOfYear.php
+++ b/src/Query/Mysql/DayOfYear.php
@@ -17,7 +17,7 @@ class DayOfYear extends FunctionNode
     /**
      * @inheritdoc
      */
-    public function getSql(SqlWalker $sqlWalker)
+    public function getSql(SqlWalker $sqlWalker): string
     {
         return 'DAYOFYEAR(' . $sqlWalker->walkArithmeticPrimary($this->date) . ')';
     }
@@ -25,7 +25,7 @@ public function getSql(SqlWalker $sqlWalker)
     /**
      * @inheritdoc
      */
-    public function parse(Parser $parser)
+    public function parse(Parser $parser): void
     {
         $parser->match(Lexer::T_IDENTIFIER);
         $parser->match(Lexer::T_OPEN_PARENTHESIS);
diff --git a/src/Query/Mysql/Degrees.php b/src/Query/Mysql/Degrees.php
index 9185d64f..b516cf74 100644
--- a/src/Query/Mysql/Degrees.php
+++ b/src/Query/Mysql/Degrees.php
@@ -9,7 +9,7 @@ class Degrees extends FunctionNode
 {
     public $arithmeticExpression;
 
-    public function getSql(\Doctrine\ORM\Query\SqlWalker $sqlWalker)
+    public function getSql(\Doctrine\ORM\Query\SqlWalker $sqlWalker): string
     {
         return 'DEGREES(' .
             $sqlWalker->walkSimpleArithmeticExpression(
@@ -18,7 +18,7 @@ public function getSql(\Doctrine\ORM\Query\SqlWalker $sqlWalker)
         ')';
     }
 
-    public function parse(\Doctrine\ORM\Query\Parser $parser)
+    public function parse(\Doctrine\ORM\Query\Parser $parser): void
     {
         $parser->match(Lexer::T_IDENTIFIER);
         $parser->match(Lexer::T_OPEN_PARENTHESIS);
diff --git a/src/Query/Mysql/Div.php b/src/Query/Mysql/Div.php
index cdc13b50..1d86b8bc 100644
--- a/src/Query/Mysql/Div.php
+++ b/src/Query/Mysql/Div.php
@@ -25,7 +25,7 @@ class Div extends FunctionNode
     /**
      * @inheritdoc
      */
-    public function getSql(SqlWalker $sqlWalker)
+    public function getSql(SqlWalker $sqlWalker): string
     {
         return
             $sqlWalker->walkArithmeticPrimary($this->dividend) . ' DIV ' .
@@ -35,7 +35,7 @@ public function getSql(SqlWalker $sqlWalker)
     /**
      * @inheritdoc
      */
-    public function parse(Parser $parser)
+    public function parse(Parser $parser): void
     {
         $parser->match(Lexer::T_IDENTIFIER);
         $parser->match(Lexer::T_OPEN_PARENTHESIS);
diff --git a/src/Query/Mysql/Exp.php b/src/Query/Mysql/Exp.php
index 82769ef3..c119f40f 100644
--- a/src/Query/Mysql/Exp.php
+++ b/src/Query/Mysql/Exp.php
@@ -9,14 +9,14 @@ class Exp extends FunctionNode
 {
     public $arithmeticExpression;
 
-    public function getSql(\Doctrine\ORM\Query\SqlWalker $sqlWalker)
+    public function getSql(\Doctrine\ORM\Query\SqlWalker $sqlWalker): string
     {
         return 'EXP(' . $sqlWalker->walkSimpleArithmeticExpression(
             $this->arithmeticExpression
         ) . ')';
     }
 
-    public function parse(\Doctrine\ORM\Query\Parser $parser)
+    public function parse(\Doctrine\ORM\Query\Parser $parser): void
     {
         $parser->match(Lexer::T_IDENTIFIER);
         $parser->match(Lexer::T_OPEN_PARENTHESIS);
diff --git a/src/Query/Mysql/Extract.php b/src/Query/Mysql/Extract.php
index 392c9506..d6d9c31e 100644
--- a/src/Query/Mysql/Extract.php
+++ b/src/Query/Mysql/Extract.php
@@ -14,7 +14,7 @@ class Extract extends DateAdd
 
     public $unit = null;
 
-    public function parse(\Doctrine\ORM\Query\Parser $parser)
+    public function parse(\Doctrine\ORM\Query\Parser $parser): void
     {
         $parser->match(Lexer::T_IDENTIFIER);
         $parser->match(Lexer::T_OPEN_PARENTHESIS);
@@ -29,7 +29,7 @@ public function parse(\Doctrine\ORM\Query\Parser $parser)
         $parser->match(Lexer::T_CLOSE_PARENTHESIS);
     }
 
-    public function getSql(\Doctrine\ORM\Query\SqlWalker $sqlWalker)
+    public function getSql(\Doctrine\ORM\Query\SqlWalker $sqlWalker): string
     {
         $unit = strtoupper($this->unit);
         if (!in_array($unit, self::$allowedUnits)) {
diff --git a/src/Query/Mysql/Field.php b/src/Query/Mysql/Field.php
index 0091415f..45849d68 100644
--- a/src/Query/Mysql/Field.php
+++ b/src/Query/Mysql/Field.php
@@ -14,7 +14,7 @@ class Field extends FunctionNode
 
     private $values = [];
 
-    public function parse(\Doctrine\ORM\Query\Parser $parser)
+    public function parse(\Doctrine\ORM\Query\Parser $parser): void
     {
         $parser->match(Lexer::T_IDENTIFIER);
         $parser->match(Lexer::T_OPEN_PARENTHESIS);
@@ -36,7 +36,7 @@ public function parse(\Doctrine\ORM\Query\Parser $parser)
         $parser->match(Lexer::T_CLOSE_PARENTHESIS);
     }
 
-    public function getSql(\Doctrine\ORM\Query\SqlWalker $sqlWalker)
+    public function getSql(\Doctrine\ORM\Query\SqlWalker $sqlWalker): string
     {
         $query = 'FIELD(';
 
diff --git a/src/Query/Mysql/FindInSet.php b/src/Query/Mysql/FindInSet.php
index 447ae5f2..5b31c787 100644
--- a/src/Query/Mysql/FindInSet.php
+++ b/src/Query/Mysql/FindInSet.php
@@ -11,7 +11,7 @@ class FindInSet extends FunctionNode
 
     public $haystack = null;
 
-    public function parse(\Doctrine\ORM\Query\Parser $parser)
+    public function parse(\Doctrine\ORM\Query\Parser $parser): void
     {
         $parser->match(Lexer::T_IDENTIFIER);
         $parser->match(Lexer::T_OPEN_PARENTHESIS);
@@ -21,7 +21,7 @@ public function parse(\Doctrine\ORM\Query\Parser $parser)
         $parser->match(Lexer::T_CLOSE_PARENTHESIS);
     }
 
-    public function getSql(\Doctrine\ORM\Query\SqlWalker $sqlWalker)
+    public function getSql(\Doctrine\ORM\Query\SqlWalker $sqlWalker): string
     {
         return 'FIND_IN_SET(' .
             $this->needle->dispatch($sqlWalker) . ', ' .
diff --git a/src/Query/Mysql/Floor.php b/src/Query/Mysql/Floor.php
index cd0e064f..7e89a983 100644
--- a/src/Query/Mysql/Floor.php
+++ b/src/Query/Mysql/Floor.php
@@ -9,12 +9,12 @@ class Floor extends FunctionNode
 {
     private $arithmeticExpression;
 
-    public function getSql(\Doctrine\ORM\Query\SqlWalker $sqlWalker)
+    public function getSql(\Doctrine\ORM\Query\SqlWalker $sqlWalker): string
     {
         return 'FLOOR(' . $sqlWalker->walkSimpleArithmeticExpression($this->arithmeticExpression) . ')';
     }
 
-    public function parse(\Doctrine\ORM\Query\Parser $parser)
+    public function parse(\Doctrine\ORM\Query\Parser $parser): void
     {
         $parser->match(Lexer::T_IDENTIFIER);
         $parser->match(Lexer::T_OPEN_PARENTHESIS);
diff --git a/src/Query/Mysql/Format.php b/src/Query/Mysql/Format.php
index a861c97c..469a6b35 100644
--- a/src/Query/Mysql/Format.php
+++ b/src/Query/Mysql/Format.php
@@ -14,7 +14,7 @@ class Format extends FunctionNode
 
     public $patternExpression = null;
 
-    public function parse(\Doctrine\ORM\Query\Parser $parser)
+    public function parse(\Doctrine\ORM\Query\Parser $parser): void
     {
         $parser->match(Lexer::T_IDENTIFIER);
         $parser->match(Lexer::T_OPEN_PARENTHESIS);
@@ -24,7 +24,7 @@ public function parse(\Doctrine\ORM\Query\Parser $parser)
         $parser->match(Lexer::T_CLOSE_PARENTHESIS);
     }
 
-    public function getSql(\Doctrine\ORM\Query\SqlWalker $sqlWalker)
+    public function getSql(\Doctrine\ORM\Query\SqlWalker $sqlWalker): string
     {
         return 'FORMAT(' .
             $this->numberExpression->dispatch($sqlWalker) . ', ' .
diff --git a/src/Query/Mysql/FromBase64.php b/src/Query/Mysql/FromBase64.php
index d0aa545f..13ae69ac 100644
--- a/src/Query/Mysql/FromBase64.php
+++ b/src/Query/Mysql/FromBase64.php
@@ -18,7 +18,7 @@ class FromBase64 extends FunctionNode
 {
     public $field = null;
 
-    public function parse(Parser $parser)
+    public function parse(Parser $parser): void
     {
         $parser->match(Lexer::T_IDENTIFIER);
         $parser->match(Lexer::T_OPEN_PARENTHESIS);
@@ -26,7 +26,7 @@ public function parse(Parser $parser)
         $parser->match(Lexer::T_CLOSE_PARENTHESIS);
     }
 
-    public function getSql(SqlWalker $sqlWalker)
+    public function getSql(SqlWalker $sqlWalker): string
     {
         return 'FROM_BASE64(' . $this->field->dispatch($sqlWalker) . ')';
     }
diff --git a/src/Query/Mysql/FromUnixtime.php b/src/Query/Mysql/FromUnixtime.php
index f74fa6bc..7bd20341 100644
--- a/src/Query/Mysql/FromUnixtime.php
+++ b/src/Query/Mysql/FromUnixtime.php
@@ -14,7 +14,7 @@ class FromUnixtime extends FunctionNode
 
     public $secondExpression = null;
 
-    public function getSql(\Doctrine\ORM\Query\SqlWalker $sqlWalker)
+    public function getSql(\Doctrine\ORM\Query\SqlWalker $sqlWalker): string
     {
         if (null !== $this->secondExpression) {
             return 'FROM_UNIXTIME('
@@ -27,7 +27,7 @@ public function getSql(\Doctrine\ORM\Query\SqlWalker $sqlWalker)
         return 'FROM_UNIXTIME(' . $this->firstExpression->dispatch($sqlWalker) . ')';
     }
 
-    public function parse(\Doctrine\ORM\Query\Parser $parser)
+    public function parse(\Doctrine\ORM\Query\Parser $parser): void
     {
         $lexer = $parser->getLexer();
 
diff --git a/src/Query/Mysql/Greatest.php b/src/Query/Mysql/Greatest.php
index b370a19b..96734f4c 100644
--- a/src/Query/Mysql/Greatest.php
+++ b/src/Query/Mysql/Greatest.php
@@ -20,7 +20,7 @@ class Greatest extends FunctionNode
     /**
      * @param Parser $parser
      */
-    public function parse(Parser $parser)
+    public function parse(Parser $parser): void
     {
         $parser->match(Lexer::T_IDENTIFIER);
         $parser->match(Lexer::T_OPEN_PARENTHESIS);
@@ -40,7 +40,7 @@ public function parse(Parser $parser)
      * @param SqlWalker $sqlWalker
      * @return string
      */
-    public function getSql(SqlWalker $sqlWalker)
+    public function getSql(SqlWalker $sqlWalker): string
     {
         $query = 'GREATEST(';
 
diff --git a/src/Query/Mysql/GroupConcat.php b/src/Query/Mysql/GroupConcat.php
index 09d6c5c9..970ff2a7 100644
--- a/src/Query/Mysql/GroupConcat.php
+++ b/src/Query/Mysql/GroupConcat.php
@@ -15,7 +15,7 @@ class GroupConcat extends FunctionNode
 
     public $orderBy = null;
 
-    public function parse(\Doctrine\ORM\Query\Parser $parser)
+    public function parse(\Doctrine\ORM\Query\Parser $parser): void
     {
         $parser->match(Lexer::T_IDENTIFIER);
         $parser->match(Lexer::T_OPEN_PARENTHESIS);
@@ -56,7 +56,7 @@ public function parse(\Doctrine\ORM\Query\Parser $parser)
         $parser->match(Lexer::T_CLOSE_PARENTHESIS);
     }
 
-    public function getSql(\Doctrine\ORM\Query\SqlWalker $sqlWalker)
+    public function getSql(\Doctrine\ORM\Query\SqlWalker $sqlWalker): string
     {
         $result = 'GROUP_CONCAT(' . ($this->isDistinct ? 'DISTINCT ' : '');
 
diff --git a/src/Query/Mysql/Hex.php b/src/Query/Mysql/Hex.php
index fdca526e..716992df 100644
--- a/src/Query/Mysql/Hex.php
+++ b/src/Query/Mysql/Hex.php
@@ -9,12 +9,12 @@ class Hex extends FunctionNode
 {
     public $arithmeticExpression;
 
-    public function getSql(\Doctrine\ORM\Query\SqlWalker $sqlWalker)
+    public function getSql(\Doctrine\ORM\Query\SqlWalker $sqlWalker): string
     {
         return 'HEX(' . $sqlWalker->walkSimpleArithmeticExpression($this->arithmeticExpression) . ')';
     }
 
-    public function parse(\Doctrine\ORM\Query\Parser $parser)
+    public function parse(\Doctrine\ORM\Query\Parser $parser): void
     {
         $parser->match(Lexer::T_IDENTIFIER);
         $parser->match(Lexer::T_OPEN_PARENTHESIS);
diff --git a/src/Query/Mysql/Hour.php b/src/Query/Mysql/Hour.php
index dbe403c2..9a6817c9 100644
--- a/src/Query/Mysql/Hour.php
+++ b/src/Query/Mysql/Hour.php
@@ -12,12 +12,12 @@ class Hour extends FunctionNode
 {
     public $date;
 
-    public function getSql(\Doctrine\ORM\Query\SqlWalker $sqlWalker)
+    public function getSql(\Doctrine\ORM\Query\SqlWalker $sqlWalker): string
     {
         return 'HOUR('.$sqlWalker->walkArithmeticPrimary($this->date).')';
     }
 
-    public function parse(\Doctrine\ORM\Query\Parser $parser)
+    public function parse(\Doctrine\ORM\Query\Parser $parser): void
     {
         $parser->match(Lexer::T_IDENTIFIER);
         $parser->match(Lexer::T_OPEN_PARENTHESIS);
diff --git a/src/Query/Mysql/IfElse.php b/src/Query/Mysql/IfElse.php
index c506f21f..1493ba2b 100644
--- a/src/Query/Mysql/IfElse.php
+++ b/src/Query/Mysql/IfElse.php
@@ -12,7 +12,7 @@ class IfElse extends FunctionNode
 {
     private $expr = [];
 
-    public function parse(\Doctrine\ORM\Query\Parser $parser)
+    public function parse(\Doctrine\ORM\Query\Parser $parser): void
     {
         $parser->match(Lexer::T_IDENTIFIER);
         $parser->match(Lexer::T_OPEN_PARENTHESIS);
@@ -36,7 +36,7 @@ public function parse(\Doctrine\ORM\Query\Parser $parser)
         $parser->match(Lexer::T_CLOSE_PARENTHESIS);
     }
 
-    public function getSql(\Doctrine\ORM\Query\SqlWalker $sqlWalker)
+    public function getSql(\Doctrine\ORM\Query\SqlWalker $sqlWalker): string
     {
         return sprintf(
             'IF(%s, %s, %s)',
diff --git a/src/Query/Mysql/IfNull.php b/src/Query/Mysql/IfNull.php
index f82cc5a3..26d32e77 100644
--- a/src/Query/Mysql/IfNull.php
+++ b/src/Query/Mysql/IfNull.php
@@ -14,7 +14,7 @@ class IfNull extends FunctionNode
 
     private $expr2;
 
-    public function parse(\Doctrine\ORM\Query\Parser $parser)
+    public function parse(\Doctrine\ORM\Query\Parser $parser): void
     {
         $parser->match(Lexer::T_IDENTIFIER);
         $parser->match(Lexer::T_OPEN_PARENTHESIS);
@@ -24,7 +24,7 @@ public function parse(\Doctrine\ORM\Query\Parser $parser)
         $parser->match(Lexer::T_CLOSE_PARENTHESIS);
     }
 
-    public function getSql(\Doctrine\ORM\Query\SqlWalker $sqlWalker)
+    public function getSql(\Doctrine\ORM\Query\SqlWalker $sqlWalker): string
     {
         return 'IFNULL('
             .$sqlWalker->walkArithmeticPrimary($this->expr1). ', '
diff --git a/src/Query/Mysql/Inet6Aton.php b/src/Query/Mysql/Inet6Aton.php
index 76482b1e..430e5fc1 100644
--- a/src/Query/Mysql/Inet6Aton.php
+++ b/src/Query/Mysql/Inet6Aton.php
@@ -18,7 +18,7 @@ class Inet6Aton extends FunctionNode
      *
      * @throws QueryException
      */
-    public function parse(Parser $parser)
+    public function parse(Parser $parser): void
     {
         $parser->match(Lexer::T_IDENTIFIER);
         $parser->match(Lexer::T_OPEN_PARENTHESIS);
@@ -31,7 +31,7 @@ public function parse(Parser $parser)
      *
      * @return string
      */
-    public function getSql(SqlWalker $sqlWalker)
+    public function getSql(SqlWalker $sqlWalker): string
     {
         return 'INET6_ATON('
             . (
diff --git a/src/Query/Mysql/Inet6Ntoa.php b/src/Query/Mysql/Inet6Ntoa.php
index 968eb523..5d641271 100644
--- a/src/Query/Mysql/Inet6Ntoa.php
+++ b/src/Query/Mysql/Inet6Ntoa.php
@@ -18,7 +18,7 @@ class Inet6Ntoa extends FunctionNode
      *
      * @throws QueryException
      */
-    public function parse(Parser $parser)
+    public function parse(Parser $parser): void
     {
         $parser->match(Lexer::T_IDENTIFIER);
         $parser->match(Lexer::T_OPEN_PARENTHESIS);
@@ -31,7 +31,7 @@ public function parse(Parser $parser)
      *
      * @return string
      */
-    public function getSql(SqlWalker $sqlWalker)
+    public function getSql(SqlWalker $sqlWalker): string
     {
         return 'INET6_NTOA('
             . (
diff --git a/src/Query/Mysql/InetAton.php b/src/Query/Mysql/InetAton.php
index c15755a5..a03e8530 100644
--- a/src/Query/Mysql/InetAton.php
+++ b/src/Query/Mysql/InetAton.php
@@ -18,7 +18,7 @@ class InetAton extends FunctionNode
      *
      * @throws QueryException
      */
-    public function parse(Parser $parser)
+    public function parse(Parser $parser): void
     {
         $parser->match(Lexer::T_IDENTIFIER);
         $parser->match(Lexer::T_OPEN_PARENTHESIS);
@@ -31,7 +31,7 @@ public function parse(Parser $parser)
      *
      * @return string
      */
-    public function getSql(SqlWalker $sqlWalker)
+    public function getSql(SqlWalker $sqlWalker): string
     {
         return 'INET_ATON('
             . (
diff --git a/src/Query/Mysql/InetNtoa.php b/src/Query/Mysql/InetNtoa.php
index a79182bd..4e2f55d2 100644
--- a/src/Query/Mysql/InetNtoa.php
+++ b/src/Query/Mysql/InetNtoa.php
@@ -18,7 +18,7 @@ class InetNtoa extends FunctionNode
      *
      * @throws QueryException
      */
-    public function parse(Parser $parser)
+    public function parse(Parser $parser): void
     {
         $parser->match(Lexer::T_IDENTIFIER);
         $parser->match(Lexer::T_OPEN_PARENTHESIS);
@@ -31,7 +31,7 @@ public function parse(Parser $parser)
      *
      * @return string
      */
-    public function getSql(SqlWalker $sqlWalker)
+    public function getSql(SqlWalker $sqlWalker): string
     {
         return 'INET_NTOA('
             . (
diff --git a/src/Query/Mysql/Instr.php b/src/Query/Mysql/Instr.php
index 3cc8a876..e939bdbb 100644
--- a/src/Query/Mysql/Instr.php
+++ b/src/Query/Mysql/Instr.php
@@ -16,7 +16,7 @@ class Instr extends FunctionNode
     /**
      * @param \Doctrine\ORM\Query\Parser $parser
      */
-    public function parse(Parser $parser)
+    public function parse(Parser $parser): void
     {
         $parser->match(Lexer::T_IDENTIFIER);
         $parser->match(Lexer::T_OPEN_PARENTHESIS);
@@ -30,7 +30,7 @@ public function parse(Parser $parser)
      * @param \Doctrine\ORM\Query\SqlWalker $sqlWalker
      * @return string
      */
-    public function getSql(SqlWalker $sqlWalker)
+    public function getSql(SqlWalker $sqlWalker): string
     {
         return sprintf(
             'INSTR(%s, %s)',
diff --git a/src/Query/Mysql/IsIpv4.php b/src/Query/Mysql/IsIpv4.php
index e0e1b9c0..959b6e6d 100644
--- a/src/Query/Mysql/IsIpv4.php
+++ b/src/Query/Mysql/IsIpv4.php
@@ -18,7 +18,7 @@ class IsIpv4 extends FunctionNode
      *
      * @throws QueryException
      */
-    public function parse(Parser $parser)
+    public function parse(Parser $parser): void
     {
         $parser->match(Lexer::T_IDENTIFIER);
         $parser->match(Lexer::T_OPEN_PARENTHESIS);
@@ -31,7 +31,7 @@ public function parse(Parser $parser)
      *
      * @return string
      */
-    public function getSql(SqlWalker $sqlWalker)
+    public function getSql(SqlWalker $sqlWalker): string
     {
         return 'IS_IPV4('
             . (
diff --git a/src/Query/Mysql/IsIpv4Compat.php b/src/Query/Mysql/IsIpv4Compat.php
index 8324a255..13e221a2 100644
--- a/src/Query/Mysql/IsIpv4Compat.php
+++ b/src/Query/Mysql/IsIpv4Compat.php
@@ -18,7 +18,7 @@ class IsIpv4Compat extends FunctionNode
      *
      * @throws QueryException
      */
-    public function parse(Parser $parser)
+    public function parse(Parser $parser): void
     {
         $parser->match(Lexer::T_IDENTIFIER);
         $parser->match(Lexer::T_OPEN_PARENTHESIS);
@@ -31,7 +31,7 @@ public function parse(Parser $parser)
      *
      * @return string
      */
-    public function getSql(SqlWalker $sqlWalker)
+    public function getSql(SqlWalker $sqlWalker): string
     {
         return 'IS_IPV4_COMPAT('
             . (
diff --git a/src/Query/Mysql/IsIpv4Mapped.php b/src/Query/Mysql/IsIpv4Mapped.php
index 56171377..e8f91e2f 100644
--- a/src/Query/Mysql/IsIpv4Mapped.php
+++ b/src/Query/Mysql/IsIpv4Mapped.php
@@ -18,7 +18,7 @@ class IsIpv4Mapped extends FunctionNode
      *
      * @throws QueryException
      */
-    public function parse(Parser $parser)
+    public function parse(Parser $parser): void
     {
         $parser->match(Lexer::T_IDENTIFIER);
         $parser->match(Lexer::T_OPEN_PARENTHESIS);
@@ -31,7 +31,7 @@ public function parse(Parser $parser)
      *
      * @return string
      */
-    public function getSql(SqlWalker $sqlWalker)
+    public function getSql(SqlWalker $sqlWalker): string
     {
         return 'IS_IPV4_MAPPED('
             . (
diff --git a/src/Query/Mysql/IsIpv6.php b/src/Query/Mysql/IsIpv6.php
index d421b0cd..1bb1d453 100644
--- a/src/Query/Mysql/IsIpv6.php
+++ b/src/Query/Mysql/IsIpv6.php
@@ -18,7 +18,7 @@ class IsIpv6 extends FunctionNode
      *
      * @throws QueryException
      */
-    public function parse(Parser $parser)
+    public function parse(Parser $parser): void
     {
         $parser->match(Lexer::T_IDENTIFIER);
         $parser->match(Lexer::T_OPEN_PARENTHESIS);
@@ -31,7 +31,7 @@ public function parse(Parser $parser)
      *
      * @return string
      */
-    public function getSql(SqlWalker $sqlWalker)
+    public function getSql(SqlWalker $sqlWalker): string
     {
         return 'IS_IPV6('
             . (
diff --git a/src/Query/Mysql/JsonContains.php b/src/Query/Mysql/JsonContains.php
index 4dd4e421..e307225b 100644
--- a/src/Query/Mysql/JsonContains.php
+++ b/src/Query/Mysql/JsonContains.php
@@ -15,7 +15,7 @@ class JsonContains extends FunctionNode
 
     protected $path;
 
-    public function parse(Parser $parser)
+    public function parse(Parser $parser): void
     {
         $parser->match(Lexer::T_IDENTIFIER);
         $parser->match(Lexer::T_OPEN_PARENTHESIS);
@@ -35,7 +35,7 @@ public function parse(Parser $parser)
         $parser->match(Lexer::T_CLOSE_PARENTHESIS);
     }
 
-    public function getSql(SqlWalker $sqlWalker)
+    public function getSql(SqlWalker $sqlWalker): string
     {
         $target = $sqlWalker->walkStringPrimary($this->target);
         $candidate = $sqlWalker->walkStringPrimary($this->candidate);
diff --git a/src/Query/Mysql/JsonDepth.php b/src/Query/Mysql/JsonDepth.php
index fb8f7f19..cfbaa2b0 100644
--- a/src/Query/Mysql/JsonDepth.php
+++ b/src/Query/Mysql/JsonDepth.php
@@ -11,7 +11,7 @@ class JsonDepth extends FunctionNode
 {
     protected $target;
 
-    public function parse(Parser $parser)
+    public function parse(Parser $parser): void
     {
         $parser->match(Lexer::T_IDENTIFIER);
         $parser->match(Lexer::T_OPEN_PARENTHESIS);
@@ -21,7 +21,7 @@ public function parse(Parser $parser)
         $parser->match(Lexer::T_CLOSE_PARENTHESIS);
     }
 
-    public function getSql(SqlWalker $sqlWalker)
+    public function getSql(SqlWalker $sqlWalker): string
     {
         return sprintf('JSON_DEPTH(%s)', $sqlWalker->walkStringPrimary($this->target));
     }
diff --git a/src/Query/Mysql/JsonLength.php b/src/Query/Mysql/JsonLength.php
index efe8990d..e7731a51 100644
--- a/src/Query/Mysql/JsonLength.php
+++ b/src/Query/Mysql/JsonLength.php
@@ -13,7 +13,7 @@ class JsonLength extends FunctionNode
 
     protected $path;
 
-    public function parse(Parser $parser)
+    public function parse(Parser $parser): void
     {
         $parser->match(Lexer::T_IDENTIFIER);
         $parser->match(Lexer::T_OPEN_PARENTHESIS);
@@ -29,7 +29,7 @@ public function parse(Parser $parser)
         $parser->match(Lexer::T_CLOSE_PARENTHESIS);
     }
 
-    public function getSql(SqlWalker $sqlWalker)
+    public function getSql(SqlWalker $sqlWalker): string
     {
         $target = $sqlWalker->walkStringPrimary($this->target);
 
diff --git a/src/Query/Mysql/LastDay.php b/src/Query/Mysql/LastDay.php
index 1f7b5f88..bc167ff8 100644
--- a/src/Query/Mysql/LastDay.php
+++ b/src/Query/Mysql/LastDay.php
@@ -13,12 +13,12 @@ class LastDay extends FunctionNode
 {
     public $date;
 
-    public function getSql(\Doctrine\ORM\Query\SqlWalker $sqlWalker)
+    public function getSql(\Doctrine\ORM\Query\SqlWalker $sqlWalker): string
     {
         return 'LAST_DAY(' . $sqlWalker->walkArithmeticPrimary($this->date) . ')';
     }
 
-    public function parse(\Doctrine\ORM\Query\Parser $parser)
+    public function parse(\Doctrine\ORM\Query\Parser $parser): void
     {
         $parser->match(Lexer::T_IDENTIFIER);
         $parser->match(Lexer::T_OPEN_PARENTHESIS);
diff --git a/src/Query/Mysql/Least.php b/src/Query/Mysql/Least.php
index 1338b38e..20a57ad3 100644
--- a/src/Query/Mysql/Least.php
+++ b/src/Query/Mysql/Least.php
@@ -19,7 +19,7 @@ class Least extends FunctionNode
     /**
      * @param Parser $parser
      */
-    public function parse(Parser $parser)
+    public function parse(Parser $parser): void
     {
         $parser->match(Lexer::T_IDENTIFIER);
         $parser->match(Lexer::T_OPEN_PARENTHESIS);
@@ -39,7 +39,7 @@ public function parse(Parser $parser)
      * @param SqlWalker $sqlWalker
      * @return string
      */
-    public function getSql(SqlWalker $sqlWalker)
+    public function getSql(SqlWalker $sqlWalker): string
     {
         $query = 'LEAST(';
 
diff --git a/src/Query/Mysql/Log.php b/src/Query/Mysql/Log.php
index ea8db45f..28c6afd7 100644
--- a/src/Query/Mysql/Log.php
+++ b/src/Query/Mysql/Log.php
@@ -9,14 +9,14 @@ class Log extends FunctionNode
 {
     public $arithmeticExpression;
 
-    public function getSql(\Doctrine\ORM\Query\SqlWalker $sqlWalker)
+    public function getSql(\Doctrine\ORM\Query\SqlWalker $sqlWalker): string
     {
         return 'LOG(' . $sqlWalker->walkSimpleArithmeticExpression(
             $this->arithmeticExpression
         ) . ')';
     }
 
-    public function parse(\Doctrine\ORM\Query\Parser $parser)
+    public function parse(\Doctrine\ORM\Query\Parser $parser): void
     {
         $parser->match(Lexer::T_IDENTIFIER);
         $parser->match(Lexer::T_OPEN_PARENTHESIS);
diff --git a/src/Query/Mysql/Log10.php b/src/Query/Mysql/Log10.php
index 5ec8b849..f5fd868a 100644
--- a/src/Query/Mysql/Log10.php
+++ b/src/Query/Mysql/Log10.php
@@ -9,14 +9,14 @@ class Log10 extends FunctionNode
 {
     public $arithmeticExpression;
 
-    public function getSql(\Doctrine\ORM\Query\SqlWalker $sqlWalker)
+    public function getSql(\Doctrine\ORM\Query\SqlWalker $sqlWalker): string
     {
         return 'LOG10(' . $sqlWalker->walkSimpleArithmeticExpression(
             $this->arithmeticExpression
         ) . ')';
     }
 
-    public function parse(\Doctrine\ORM\Query\Parser $parser)
+    public function parse(\Doctrine\ORM\Query\Parser $parser): void
     {
         $parser->match(Lexer::T_IDENTIFIER);
         $parser->match(Lexer::T_OPEN_PARENTHESIS);
diff --git a/src/Query/Mysql/Log2.php b/src/Query/Mysql/Log2.php
index 9ea6b8da..6cae3d94 100644
--- a/src/Query/Mysql/Log2.php
+++ b/src/Query/Mysql/Log2.php
@@ -9,14 +9,14 @@ class Log2 extends FunctionNode
 {
     public $arithmeticExpression;
 
-    public function getSql(\Doctrine\ORM\Query\SqlWalker $sqlWalker)
+    public function getSql(\Doctrine\ORM\Query\SqlWalker $sqlWalker): string
     {
         return 'LOG2(' . $sqlWalker->walkSimpleArithmeticExpression(
             $this->arithmeticExpression
         ) . ')';
     }
 
-    public function parse(\Doctrine\ORM\Query\Parser $parser)
+    public function parse(\Doctrine\ORM\Query\Parser $parser): void
     {
         $parser->match(Lexer::T_IDENTIFIER);
         $parser->match(Lexer::T_OPEN_PARENTHESIS);
diff --git a/src/Query/Mysql/Lpad.php b/src/Query/Mysql/Lpad.php
index d552b792..cf20dd70 100644
--- a/src/Query/Mysql/Lpad.php
+++ b/src/Query/Mysql/Lpad.php
@@ -16,7 +16,7 @@ class Lpad extends FunctionNode
 
     public $padstring = null;
 
-    public function parse(\Doctrine\ORM\Query\Parser $parser)
+    public function parse(\Doctrine\ORM\Query\Parser $parser): void
     {
         $parser->match(Lexer::T_IDENTIFIER);
         $parser->match(Lexer::T_OPEN_PARENTHESIS);
@@ -28,7 +28,7 @@ public function parse(\Doctrine\ORM\Query\Parser $parser)
         $parser->match(Lexer::T_CLOSE_PARENTHESIS);
     }
 
-    public function getSql(\Doctrine\ORM\Query\SqlWalker $sqlWalker)
+    public function getSql(\Doctrine\ORM\Query\SqlWalker $sqlWalker): string
     {
         return 'LPAD(' .
         $this->string->dispatch($sqlWalker) . ', ' .
diff --git a/src/Query/Mysql/MakeDate.php b/src/Query/Mysql/MakeDate.php
index 6d90e48d..37a8253b 100644
--- a/src/Query/Mysql/MakeDate.php
+++ b/src/Query/Mysql/MakeDate.php
@@ -11,7 +11,7 @@ class MakeDate extends FunctionNode
 
     public $dayOfYear = null;
 
-    public function parse(\Doctrine\ORM\Query\Parser $parser)
+    public function parse(\Doctrine\ORM\Query\Parser $parser): void
     {
         $parser->match(Lexer::T_IDENTIFIER);
         $parser->match(Lexer::T_OPEN_PARENTHESIS);
@@ -21,7 +21,7 @@ public function parse(\Doctrine\ORM\Query\Parser $parser)
         $parser->match(Lexer::T_CLOSE_PARENTHESIS);
     }
 
-    public function getSql(\Doctrine\ORM\Query\SqlWalker $sqlWalker)
+    public function getSql(\Doctrine\ORM\Query\SqlWalker $sqlWalker): string
     {
         return 'MAKEDATE('.
             $sqlWalker->walkArithmeticPrimary($this->year).', '.
diff --git a/src/Query/Mysql/MatchAgainst.php b/src/Query/Mysql/MatchAgainst.php
index ffc1ed00..c9a7b4ae 100644
--- a/src/Query/Mysql/MatchAgainst.php
+++ b/src/Query/Mysql/MatchAgainst.php
@@ -19,7 +19,7 @@ class MatchAgainst extends FunctionNode
     /** @var bool */
     protected $queryExpansion = false;
 
-    public function parse(\Doctrine\ORM\Query\Parser $parser)
+    public function parse(\Doctrine\ORM\Query\Parser $parser): void
     {
         // match
         $parser->match(Lexer::T_IDENTIFIER);
@@ -88,7 +88,7 @@ public function parse(\Doctrine\ORM\Query\Parser $parser)
         $parser->match(Lexer::T_CLOSE_PARENTHESIS);
     }
 
-    public function getSql(\Doctrine\ORM\Query\SqlWalker $walker)
+    public function getSql(\Doctrine\ORM\Query\SqlWalker $walker): string
     {
         $fields = [];
 
diff --git a/src/Query/Mysql/Md5.php b/src/Query/Mysql/Md5.php
index 84d3adcf..bb290608 100644
--- a/src/Query/Mysql/Md5.php
+++ b/src/Query/Mysql/Md5.php
@@ -12,14 +12,14 @@ class Md5 extends FunctionNode
 {
     public $stringPrimary;
 
-    public function getSql(\Doctrine\ORM\Query\SqlWalker $sqlWalker)
+    public function getSql(\Doctrine\ORM\Query\SqlWalker $sqlWalker): string
     {
         return $sqlWalker->getConnection()->getDatabasePlatform()->getMd5Expression(
             $sqlWalker->walkStringPrimary($this->stringPrimary)
         );
     }
 
-    public function parse(\Doctrine\ORM\Query\Parser $parser)
+    public function parse(\Doctrine\ORM\Query\Parser $parser): void
     {
         $parser->match(Lexer::T_IDENTIFIER);
         $parser->match(Lexer::T_OPEN_PARENTHESIS);
diff --git a/src/Query/Mysql/Minute.php b/src/Query/Mysql/Minute.php
index f436894a..84d2829a 100644
--- a/src/Query/Mysql/Minute.php
+++ b/src/Query/Mysql/Minute.php
@@ -12,12 +12,12 @@ class Minute extends FunctionNode
 {
     public $date;
 
-    public function getSql(\Doctrine\ORM\Query\SqlWalker $sqlWalker)
+    public function getSql(\Doctrine\ORM\Query\SqlWalker $sqlWalker): string
     {
         return 'MINUTE('.$sqlWalker->walkArithmeticPrimary($this->date).')';
     }
 
-    public function parse(\Doctrine\ORM\Query\Parser $parser)
+    public function parse(\Doctrine\ORM\Query\Parser $parser): void
     {
         $parser->match(Lexer::T_IDENTIFIER);
         $parser->match(Lexer::T_OPEN_PARENTHESIS);
diff --git a/src/Query/Mysql/Month.php b/src/Query/Mysql/Month.php
index 532920a1..3efc45c7 100644
--- a/src/Query/Mysql/Month.php
+++ b/src/Query/Mysql/Month.php
@@ -13,12 +13,12 @@ class Month extends FunctionNode
 {
     public $date;
 
-    public function getSql(\Doctrine\ORM\Query\SqlWalker $sqlWalker)
+    public function getSql(\Doctrine\ORM\Query\SqlWalker $sqlWalker): string
     {
         return 'MONTH(' . $sqlWalker->walkArithmeticPrimary($this->date) . ')';
     }
 
-    public function parse(\Doctrine\ORM\Query\Parser $parser)
+    public function parse(\Doctrine\ORM\Query\Parser $parser): void
     {
         $parser->match(Lexer::T_IDENTIFIER);
         $parser->match(Lexer::T_OPEN_PARENTHESIS);
diff --git a/src/Query/Mysql/MonthName.php b/src/Query/Mysql/MonthName.php
index c5976460..5b24cdec 100644
--- a/src/Query/Mysql/MonthName.php
+++ b/src/Query/Mysql/MonthName.php
@@ -12,12 +12,12 @@ class MonthName extends FunctionNode
 {
     public $date;
 
-    public function getSql(\Doctrine\ORM\Query\SqlWalker $sqlWalker)
+    public function getSql(\Doctrine\ORM\Query\SqlWalker $sqlWalker): string
     {
         return 'MONTHNAME(' . $sqlWalker->walkArithmeticPrimary($this->date) . ')';
     }
 
-    public function parse(\Doctrine\ORM\Query\Parser $parser)
+    public function parse(\Doctrine\ORM\Query\Parser $parser): void
     {
         $parser->match(Lexer::T_IDENTIFIER);
         $parser->match(Lexer::T_OPEN_PARENTHESIS);
diff --git a/src/Query/Mysql/Now.php b/src/Query/Mysql/Now.php
index ac44d9bd..dd0a4120 100644
--- a/src/Query/Mysql/Now.php
+++ b/src/Query/Mysql/Now.php
@@ -7,12 +7,12 @@
 
 class Now extends FunctionNode
 {
-    public function getSql(\Doctrine\ORM\Query\SqlWalker $sqlWalker)
+    public function getSql(\Doctrine\ORM\Query\SqlWalker $sqlWalker): string
     {
         return 'NOW()';
     }
 
-    public function parse(\Doctrine\ORM\Query\Parser $parser)
+    public function parse(\Doctrine\ORM\Query\Parser $parser): void
     {
         $parser->match(Lexer::T_IDENTIFIER);
         $parser->match(Lexer::T_OPEN_PARENTHESIS);
diff --git a/src/Query/Mysql/NullIf.php b/src/Query/Mysql/NullIf.php
index 9c73f98f..cc77b4e5 100644
--- a/src/Query/Mysql/NullIf.php
+++ b/src/Query/Mysql/NullIf.php
@@ -14,7 +14,7 @@ class NullIf extends FunctionNode
 
     private $expr2;
 
-    public function parse(\Doctrine\ORM\Query\Parser $parser)
+    public function parse(\Doctrine\ORM\Query\Parser $parser): void
     {
         $parser->match(Lexer::T_IDENTIFIER);
         $parser->match(Lexer::T_OPEN_PARENTHESIS);
@@ -24,7 +24,7 @@ public function parse(\Doctrine\ORM\Query\Parser $parser)
         $parser->match(Lexer::T_CLOSE_PARENTHESIS);
     }
 
-    public function getSql(\Doctrine\ORM\Query\SqlWalker $sqlWalker)
+    public function getSql(\Doctrine\ORM\Query\SqlWalker $sqlWalker): string
     {
         return sprintf(
             'NULLIF(%s, %s)',
diff --git a/src/Query/Mysql/PeriodDiff.php b/src/Query/Mysql/PeriodDiff.php
index 044333e2..e6cc3f80 100644
--- a/src/Query/Mysql/PeriodDiff.php
+++ b/src/Query/Mysql/PeriodDiff.php
@@ -11,7 +11,7 @@ class PeriodDiff extends FunctionNode
 
     public $secondDateExpression = null;
 
-    public function parse(\Doctrine\ORM\Query\Parser $parser)
+    public function parse(\Doctrine\ORM\Query\Parser $parser): void
     {
         $parser->match(Lexer::T_IDENTIFIER);
         $parser->match(Lexer::T_OPEN_PARENTHESIS);
@@ -21,7 +21,7 @@ public function parse(\Doctrine\ORM\Query\Parser $parser)
         $parser->match(Lexer::T_CLOSE_PARENTHESIS);
     }
 
-    public function getSql(\Doctrine\ORM\Query\SqlWalker $sqlWalker)
+    public function getSql(\Doctrine\ORM\Query\SqlWalker $sqlWalker): string
     {
         return 'PERIOD_DIFF(' .
             $sqlWalker->walkArithmeticTerm($this->firstDateExpression) . ', ' .
diff --git a/src/Query/Mysql/Pi.php b/src/Query/Mysql/Pi.php
index d332688e..0b0173a5 100644
--- a/src/Query/Mysql/Pi.php
+++ b/src/Query/Mysql/Pi.php
@@ -9,12 +9,12 @@ class Pi extends FunctionNode
 {
     public $arithmeticExpression;
 
-    public function getSql(\Doctrine\ORM\Query\SqlWalker $sqlWalker)
+    public function getSql(\Doctrine\ORM\Query\SqlWalker $sqlWalker): string
     {
         return 'PI()';
     }
 
-    public function parse(\Doctrine\ORM\Query\Parser $parser)
+    public function parse(\Doctrine\ORM\Query\Parser $parser): void
     {
         $parser->match(Lexer::T_IDENTIFIER);
         $parser->match(Lexer::T_OPEN_PARENTHESIS);
diff --git a/src/Query/Mysql/Power.php b/src/Query/Mysql/Power.php
index 69515cc6..c1dbe27c 100644
--- a/src/Query/Mysql/Power.php
+++ b/src/Query/Mysql/Power.php
@@ -9,13 +9,13 @@ class Power extends FunctionNode
 {
     public $arithmeticExpression;
 
-    public function getSql(\Doctrine\ORM\Query\SqlWalker $sqlWalker)
+    public function getSql(\Doctrine\ORM\Query\SqlWalker $sqlWalker): string
     {
         return 'POWER(' . $this->arithmeticExpression->dispatch($sqlWalker) . ', '
          . $this->power->dispatch($sqlWalker) . ')';
     }
 
-    public function parse(\Doctrine\ORM\Query\Parser $parser)
+    public function parse(\Doctrine\ORM\Query\Parser $parser): void
     {
         $parser->match(Lexer::T_IDENTIFIER);
         $parser->match(Lexer::T_OPEN_PARENTHESIS);
diff --git a/src/Query/Mysql/Quarter.php b/src/Query/Mysql/Quarter.php
index fb2a7f6f..b7c6465b 100644
--- a/src/Query/Mysql/Quarter.php
+++ b/src/Query/Mysql/Quarter.php
@@ -12,12 +12,12 @@ class Quarter extends FunctionNode
 {
     public $date;
 
-    public function getSql(\Doctrine\ORM\Query\SqlWalker $sqlWalker)
+    public function getSql(\Doctrine\ORM\Query\SqlWalker $sqlWalker): string
     {
         return 'QUARTER('.$sqlWalker->walkArithmeticPrimary($this->date).')';
     }
 
-    public function parse(\Doctrine\ORM\Query\Parser $parser)
+    public function parse(\Doctrine\ORM\Query\Parser $parser): void
     {
         $parser->match(Lexer::T_IDENTIFIER);
         $parser->match(Lexer::T_OPEN_PARENTHESIS);
diff --git a/src/Query/Mysql/Radians.php b/src/Query/Mysql/Radians.php
index 70788646..c829c343 100644
--- a/src/Query/Mysql/Radians.php
+++ b/src/Query/Mysql/Radians.php
@@ -9,7 +9,7 @@ class Radians extends FunctionNode
 {
     public $arithmeticExpression;
 
-    public function getSql(\Doctrine\ORM\Query\SqlWalker $sqlWalker)
+    public function getSql(\Doctrine\ORM\Query\SqlWalker $sqlWalker): string
     {
         return 'RADIANS(' .
             $sqlWalker->walkSimpleArithmeticExpression(
@@ -18,7 +18,7 @@ public function getSql(\Doctrine\ORM\Query\SqlWalker $sqlWalker)
         ')';
     }
 
-    public function parse(\Doctrine\ORM\Query\Parser $parser)
+    public function parse(\Doctrine\ORM\Query\Parser $parser): void
     {
         $parser->match(Lexer::T_IDENTIFIER);
         $parser->match(Lexer::T_OPEN_PARENTHESIS);
diff --git a/src/Query/Mysql/Rand.php b/src/Query/Mysql/Rand.php
index e3baea36..8991c2c1 100644
--- a/src/Query/Mysql/Rand.php
+++ b/src/Query/Mysql/Rand.php
@@ -13,7 +13,7 @@ class Rand extends FunctionNode
      */
     private $expression = null;
 
-    public function getSql(\Doctrine\ORM\Query\SqlWalker $sqlWalker)
+    public function getSql(\Doctrine\ORM\Query\SqlWalker $sqlWalker): string
     {
         if ($this->expression) {
             return 'RAND(' . $this->expression->dispatch($sqlWalker) . ')';
@@ -22,7 +22,7 @@ public function getSql(\Doctrine\ORM\Query\SqlWalker $sqlWalker)
         return 'RAND()';
     }
 
-    public function parse(\Doctrine\ORM\Query\Parser $parser)
+    public function parse(\Doctrine\ORM\Query\Parser $parser): void
     {
         $lexer = $parser->getLexer();
         $parser->match(Lexer::T_IDENTIFIER);
diff --git a/src/Query/Mysql/Regexp.php b/src/Query/Mysql/Regexp.php
index bd754f80..a0760697 100644
--- a/src/Query/Mysql/Regexp.php
+++ b/src/Query/Mysql/Regexp.php
@@ -11,7 +11,7 @@ class Regexp extends FunctionNode
 
     public $regexp = null;
 
-    public function parse(\Doctrine\ORM\Query\Parser $parser)
+    public function parse(\Doctrine\ORM\Query\Parser $parser): void
     {
         $parser->match(Lexer::T_IDENTIFIER);
         $parser->match(Lexer::T_OPEN_PARENTHESIS);
@@ -21,7 +21,7 @@ public function parse(\Doctrine\ORM\Query\Parser $parser)
         $parser->match(Lexer::T_CLOSE_PARENTHESIS);
     }
 
-    public function getSql(\Doctrine\ORM\Query\SqlWalker $sqlWalker)
+    public function getSql(\Doctrine\ORM\Query\SqlWalker $sqlWalker): string
     {
         return '(' . $this->value->dispatch($sqlWalker) . ' REGEXP ' . $this->regexp->dispatch($sqlWalker) . ')';
     }
diff --git a/src/Query/Mysql/Replace.php b/src/Query/Mysql/Replace.php
index 98807b23..d3ac2def 100644
--- a/src/Query/Mysql/Replace.php
+++ b/src/Query/Mysql/Replace.php
@@ -16,7 +16,7 @@ class Replace extends FunctionNode
 
     public $subject = null;
 
-    public function parse(\Doctrine\ORM\Query\Parser $parser)
+    public function parse(\Doctrine\ORM\Query\Parser $parser): void
     {
         $parser->match(Lexer::T_IDENTIFIER);
         $parser->match(Lexer::T_OPEN_PARENTHESIS);
@@ -28,7 +28,7 @@ public function parse(\Doctrine\ORM\Query\Parser $parser)
         $parser->match(Lexer::T_CLOSE_PARENTHESIS);
     }
 
-    public function getSql(\Doctrine\ORM\Query\SqlWalker $sqlWalker)
+    public function getSql(\Doctrine\ORM\Query\SqlWalker $sqlWalker): string
     {
         return 'REPLACE(' .
             $this->subject->dispatch($sqlWalker) . ', ' .
diff --git a/src/Query/Mysql/Round.php b/src/Query/Mysql/Round.php
index 9dd34914..5fe317b1 100644
--- a/src/Query/Mysql/Round.php
+++ b/src/Query/Mysql/Round.php
@@ -11,7 +11,7 @@ class Round extends FunctionNode
 
     private $secondExpression = null;
 
-    public function parse(\Doctrine\ORM\Query\Parser $parser)
+    public function parse(\Doctrine\ORM\Query\Parser $parser): void
     {
         $lexer = $parser->getLexer();
         $parser->match(Lexer::T_IDENTIFIER);
@@ -27,7 +27,7 @@ public function parse(\Doctrine\ORM\Query\Parser $parser)
         $parser->match(Lexer::T_CLOSE_PARENTHESIS);
     }
 
-    public function getSql(\Doctrine\ORM\Query\SqlWalker $sqlWalker)
+    public function getSql(\Doctrine\ORM\Query\SqlWalker $sqlWalker): string
     {
         // use second parameter if parsed
         if (null !== $this->secondExpression) {
diff --git a/src/Query/Mysql/Rpad.php b/src/Query/Mysql/Rpad.php
index c89ec3bc..bf733a6a 100644
--- a/src/Query/Mysql/Rpad.php
+++ b/src/Query/Mysql/Rpad.php
@@ -16,7 +16,7 @@ class Rpad extends FunctionNode
 
     public $padstring = null;
 
-    public function parse(\Doctrine\ORM\Query\Parser $parser)
+    public function parse(\Doctrine\ORM\Query\Parser $parser): void
     {
         $parser->match(Lexer::T_IDENTIFIER);
         $parser->match(Lexer::T_OPEN_PARENTHESIS);
@@ -28,7 +28,7 @@ public function parse(\Doctrine\ORM\Query\Parser $parser)
         $parser->match(Lexer::T_CLOSE_PARENTHESIS);
     }
 
-    public function getSql(\Doctrine\ORM\Query\SqlWalker $sqlWalker)
+    public function getSql(\Doctrine\ORM\Query\SqlWalker $sqlWalker): string
     {
         return 'RPAD(' .
         $this->string->dispatch($sqlWalker) . ', ' .
diff --git a/src/Query/Mysql/SecToTime.php b/src/Query/Mysql/SecToTime.php
index e26a365d..0816586d 100644
--- a/src/Query/Mysql/SecToTime.php
+++ b/src/Query/Mysql/SecToTime.php
@@ -14,12 +14,12 @@ class SecToTime extends FunctionNode
 {
     public $time;
 
-    public function getSql(\Doctrine\ORM\Query\SqlWalker $sqlWalker)
+    public function getSql(\Doctrine\ORM\Query\SqlWalker $sqlWalker): string
     {
         return 'SEC_TO_TIME('.$sqlWalker->walkArithmeticPrimary($this->time).')';
     }
 
-    public function parse(\Doctrine\ORM\Query\Parser $parser)
+    public function parse(\Doctrine\ORM\Query\Parser $parser): void
     {
         $parser->match(Lexer::T_IDENTIFIER);
         $parser->match(Lexer::T_OPEN_PARENTHESIS);
diff --git a/src/Query/Mysql/Second.php b/src/Query/Mysql/Second.php
index 3c54de37..c9304469 100644
--- a/src/Query/Mysql/Second.php
+++ b/src/Query/Mysql/Second.php
@@ -12,12 +12,12 @@ class Second extends FunctionNode
 {
     public $date;
 
-    public function getSql(\Doctrine\ORM\Query\SqlWalker $sqlWalker)
+    public function getSql(\Doctrine\ORM\Query\SqlWalker $sqlWalker): string
     {
         return 'SECOND('.$sqlWalker->walkArithmeticPrimary($this->date).')';
     }
 
-    public function parse(\Doctrine\ORM\Query\Parser $parser)
+    public function parse(\Doctrine\ORM\Query\Parser $parser): void
     {
         $parser->match(Lexer::T_IDENTIFIER);
         $parser->match(Lexer::T_OPEN_PARENTHESIS);
diff --git a/src/Query/Mysql/Sha1.php b/src/Query/Mysql/Sha1.php
index d3b22d62..bdb1d0aa 100644
--- a/src/Query/Mysql/Sha1.php
+++ b/src/Query/Mysql/Sha1.php
@@ -12,14 +12,14 @@ class Sha1 extends FunctionNode
 {
     public $stringPrimary;
 
-    public function getSql(\Doctrine\ORM\Query\SqlWalker $sqlWalker)
+    public function getSql(\Doctrine\ORM\Query\SqlWalker $sqlWalker): string
     {
         return 'SHA1(' .
             $sqlWalker->walkStringPrimary($this->stringPrimary) .
         ')';
     }
 
-    public function parse(\Doctrine\ORM\Query\Parser $parser)
+    public function parse(\Doctrine\ORM\Query\Parser $parser): void
     {
         $parser->match(Lexer::T_IDENTIFIER);
         $parser->match(Lexer::T_OPEN_PARENTHESIS);
diff --git a/src/Query/Mysql/Sha2.php b/src/Query/Mysql/Sha2.php
index 4a0f2018..cf23aa4f 100644
--- a/src/Query/Mysql/Sha2.php
+++ b/src/Query/Mysql/Sha2.php
@@ -14,7 +14,7 @@ class Sha2 extends FunctionNode
 
     public $simpleArithmeticExpression;
 
-    public function getSql(\Doctrine\ORM\Query\SqlWalker $sqlWalker)
+    public function getSql(\Doctrine\ORM\Query\SqlWalker $sqlWalker): string
     {
         return 'SHA2(' .
             $sqlWalker->walkStringPrimary($this->stringPrimary) .
@@ -23,7 +23,7 @@ public function getSql(\Doctrine\ORM\Query\SqlWalker $sqlWalker)
         ')';
     }
 
-    public function parse(\Doctrine\ORM\Query\Parser $parser)
+    public function parse(\Doctrine\ORM\Query\Parser $parser): void
     {
         $parser->match(Lexer::T_IDENTIFIER);
         $parser->match(Lexer::T_OPEN_PARENTHESIS);
diff --git a/src/Query/Mysql/Sin.php b/src/Query/Mysql/Sin.php
index 0be0fe4d..e40e53fb 100644
--- a/src/Query/Mysql/Sin.php
+++ b/src/Query/Mysql/Sin.php
@@ -9,14 +9,14 @@ class Sin extends FunctionNode
 {
     public $arithmeticExpression;
 
-    public function getSql(\Doctrine\ORM\Query\SqlWalker $sqlWalker)
+    public function getSql(\Doctrine\ORM\Query\SqlWalker $sqlWalker): string
     {
         return 'SIN(' . $sqlWalker->walkSimpleArithmeticExpression(
             $this->arithmeticExpression
         ) . ')';
     }
 
-    public function parse(\Doctrine\ORM\Query\Parser $parser)
+    public function parse(\Doctrine\ORM\Query\Parser $parser): void
     {
         $parser->match(Lexer::T_IDENTIFIER);
         $parser->match(Lexer::T_OPEN_PARENTHESIS);
diff --git a/src/Query/Mysql/Soundex.php b/src/Query/Mysql/Soundex.php
index 6a8e6b67..b5d39a48 100644
--- a/src/Query/Mysql/Soundex.php
+++ b/src/Query/Mysql/Soundex.php
@@ -12,12 +12,12 @@ class Soundex extends FunctionNode
 {
     public $stringPrimary;
 
-    public function getSql(\Doctrine\ORM\Query\SqlWalker $sqlWalker)
+    public function getSql(\Doctrine\ORM\Query\SqlWalker $sqlWalker): string
     {
         return 'SOUNDEX('.$sqlWalker->walkStringPrimary($this->stringPrimary).')';
     }
 
-    public function parse(\Doctrine\ORM\Query\Parser $parser)
+    public function parse(\Doctrine\ORM\Query\Parser $parser): void
     {
         $parser->match(Lexer::T_IDENTIFIER);
         $parser->match(Lexer::T_OPEN_PARENTHESIS);
diff --git a/src/Query/Mysql/Std.php b/src/Query/Mysql/Std.php
index 6d5829ff..d8b9df85 100644
--- a/src/Query/Mysql/Std.php
+++ b/src/Query/Mysql/Std.php
@@ -12,12 +12,12 @@ class Std extends FunctionNode
 {
     public $arithmeticExpression;
 
-    public function getSql(\Doctrine\ORM\Query\SqlWalker $sqlWalker)
+    public function getSql(\Doctrine\ORM\Query\SqlWalker $sqlWalker): string
     {
         return sprintf('STD(%s)', $sqlWalker->walkSimpleArithmeticExpression($this->arithmeticExpression));
     }
 
-    public function parse(\Doctrine\ORM\Query\Parser $parser)
+    public function parse(\Doctrine\ORM\Query\Parser $parser): void
     {
         $parser->match(Lexer::T_IDENTIFIER);
         $parser->match(Lexer::T_OPEN_PARENTHESIS);
diff --git a/src/Query/Mysql/StdDev.php b/src/Query/Mysql/StdDev.php
index d146818a..c25329a5 100644
--- a/src/Query/Mysql/StdDev.php
+++ b/src/Query/Mysql/StdDev.php
@@ -12,12 +12,12 @@ class StdDev extends FunctionNode
 {
     public $arithmeticExpression;
 
-    public function getSql(\Doctrine\ORM\Query\SqlWalker $sqlWalker)
+    public function getSql(\Doctrine\ORM\Query\SqlWalker $sqlWalker): string
     {
         return sprintf('STDDEV(%s)', $sqlWalker->walkSimpleArithmeticExpression($this->arithmeticExpression));
     }
 
-    public function parse(\Doctrine\ORM\Query\Parser $parser)
+    public function parse(\Doctrine\ORM\Query\Parser $parser): void
     {
         $parser->match(Lexer::T_IDENTIFIER);
         $parser->match(Lexer::T_OPEN_PARENTHESIS);
diff --git a/src/Query/Mysql/StrToDate.php b/src/Query/Mysql/StrToDate.php
index 7163999a..863caba5 100644
--- a/src/Query/Mysql/StrToDate.php
+++ b/src/Query/Mysql/StrToDate.php
@@ -11,7 +11,7 @@ class StrToDate extends FunctionNode
 
     public $dateFormat = null;
 
-    public function parse(\Doctrine\ORM\Query\Parser $parser)
+    public function parse(\Doctrine\ORM\Query\Parser $parser): void
     {
         $parser->match(Lexer::T_IDENTIFIER);
         $parser->match(Lexer::T_OPEN_PARENTHESIS);
@@ -21,7 +21,7 @@ public function parse(\Doctrine\ORM\Query\Parser $parser)
         $parser->match(Lexer::T_CLOSE_PARENTHESIS);
     }
 
-    public function getSql(\Doctrine\ORM\Query\SqlWalker $sqlWalker)
+    public function getSql(\Doctrine\ORM\Query\SqlWalker $sqlWalker): string
     {
         return 'STR_TO_DATE(' .
             $this->dateString->dispatch($sqlWalker) . ', ' .
diff --git a/src/Query/Mysql/SubstringIndex.php b/src/Query/Mysql/SubstringIndex.php
index 85a5f38f..5d05a8d1 100644
--- a/src/Query/Mysql/SubstringIndex.php
+++ b/src/Query/Mysql/SubstringIndex.php
@@ -18,7 +18,7 @@ class SubstringIndex extends FunctionNode
     /**
      * @param \Doctrine\ORM\Query\Parser $parser
      */
-    public function parse(Parser $parser)
+    public function parse(Parser $parser): void
     {
         $parser->match(Lexer::T_IDENTIFIER);
         $parser->match(Lexer::T_OPEN_PARENTHESIS);
@@ -34,7 +34,7 @@ public function parse(Parser $parser)
      * @param \Doctrine\ORM\Query\SqlWalker $sqlWalker
      * @return string
      */
-    public function getSql(SqlWalker $sqlWalker)
+    public function getSql(SqlWalker $sqlWalker): string
     {
         return sprintf(
             'SUBSTRING_INDEX(%s, %s, %s)',
diff --git a/src/Query/Mysql/Tan.php b/src/Query/Mysql/Tan.php
index c0de4484..23dd70f6 100644
--- a/src/Query/Mysql/Tan.php
+++ b/src/Query/Mysql/Tan.php
@@ -9,14 +9,14 @@ class Tan extends FunctionNode
 {
     public $arithmeticExpression;
 
-    public function getSql(\Doctrine\ORM\Query\SqlWalker $sqlWalker)
+    public function getSql(\Doctrine\ORM\Query\SqlWalker $sqlWalker): string
     {
         return 'TAN(' . $sqlWalker->walkSimpleArithmeticExpression(
             $this->arithmeticExpression
         ) . ')';
     }
 
-    public function parse(\Doctrine\ORM\Query\Parser $parser)
+    public function parse(\Doctrine\ORM\Query\Parser $parser): void
     {
         $parser->match(Lexer::T_IDENTIFIER);
         $parser->match(Lexer::T_OPEN_PARENTHESIS);
diff --git a/src/Query/Mysql/Time.php b/src/Query/Mysql/Time.php
index 04820389..dc6d2c65 100644
--- a/src/Query/Mysql/Time.php
+++ b/src/Query/Mysql/Time.php
@@ -13,12 +13,12 @@ class Time extends FunctionNode
 {
     public $time;
 
-    public function getSql(\Doctrine\ORM\Query\SqlWalker $sqlWalker)
+    public function getSql(\Doctrine\ORM\Query\SqlWalker $sqlWalker): string
     {
         return 'TIME(' . $sqlWalker->walkArithmeticPrimary($this->time) . ')';
     }
 
-    public function parse(\Doctrine\ORM\Query\Parser $parser)
+    public function parse(\Doctrine\ORM\Query\Parser $parser): void
     {
         $parser->match(Lexer::T_IDENTIFIER);
         $parser->match(Lexer::T_OPEN_PARENTHESIS);
diff --git a/src/Query/Mysql/TimeDiff.php b/src/Query/Mysql/TimeDiff.php
index 8b7da276..ede2a411 100644
--- a/src/Query/Mysql/TimeDiff.php
+++ b/src/Query/Mysql/TimeDiff.php
@@ -11,7 +11,7 @@ class TimeDiff extends FunctionNode
 
     public $secondDateExpression = null;
 
-    public function parse(\Doctrine\ORM\Query\Parser $parser)
+    public function parse(\Doctrine\ORM\Query\Parser $parser): void
     {
         $parser->match(Lexer::T_IDENTIFIER);
         $parser->match(Lexer::T_OPEN_PARENTHESIS);
@@ -21,7 +21,7 @@ public function parse(\Doctrine\ORM\Query\Parser $parser)
         $parser->match(Lexer::T_CLOSE_PARENTHESIS);
     }
 
-    public function getSql(\Doctrine\ORM\Query\SqlWalker $sqlWalker)
+    public function getSql(\Doctrine\ORM\Query\SqlWalker $sqlWalker): string
     {
         return sprintf(
             'TIMEDIFF(%s, %s)',
diff --git a/src/Query/Mysql/TimeToSec.php b/src/Query/Mysql/TimeToSec.php
index 3b4b8744..7cd27a8f 100644
--- a/src/Query/Mysql/TimeToSec.php
+++ b/src/Query/Mysql/TimeToSec.php
@@ -14,12 +14,12 @@ class TimeToSec extends FunctionNode
 {
     public $time;
 
-    public function getSql(\Doctrine\ORM\Query\SqlWalker $sqlWalker)
+    public function getSql(\Doctrine\ORM\Query\SqlWalker $sqlWalker): string
     {
         return 'TIME_TO_SEC('.$sqlWalker->walkArithmeticPrimary($this->time).')';
     }
 
-    public function parse(\Doctrine\ORM\Query\Parser $parser)
+    public function parse(\Doctrine\ORM\Query\Parser $parser): void
     {
         $parser->match(Lexer::T_IDENTIFIER);
         $parser->match(Lexer::T_OPEN_PARENTHESIS);
diff --git a/src/Query/Mysql/TimestampAdd.php b/src/Query/Mysql/TimestampAdd.php
index db623f21..43f6c615 100644
--- a/src/Query/Mysql/TimestampAdd.php
+++ b/src/Query/Mysql/TimestampAdd.php
@@ -16,7 +16,7 @@ class TimestampAdd extends FunctionNode
 
     public $unit = null;
 
-    public function parse(\Doctrine\ORM\Query\Parser $parser)
+    public function parse(\Doctrine\ORM\Query\Parser $parser): void
     {
         $parser->match(Lexer::T_IDENTIFIER);
         $parser->match(Lexer::T_OPEN_PARENTHESIS);
@@ -30,7 +30,7 @@ public function parse(\Doctrine\ORM\Query\Parser $parser)
         $parser->match(Lexer::T_CLOSE_PARENTHESIS);
     }
 
-    public function getSql(\Doctrine\ORM\Query\SqlWalker $sql_walker)
+    public function getSql(\Doctrine\ORM\Query\SqlWalker $sql_walker): string
     {
         return sprintf(
             'TIMESTAMPADD(%s, %s, %s)',
diff --git a/src/Query/Mysql/TimestampDiff.php b/src/Query/Mysql/TimestampDiff.php
index b5d3e997..c59d3aa6 100644
--- a/src/Query/Mysql/TimestampDiff.php
+++ b/src/Query/Mysql/TimestampDiff.php
@@ -16,7 +16,7 @@ class TimestampDiff extends FunctionNode
 
     public $unit = null;
 
-    public function parse(\Doctrine\ORM\Query\Parser $parser)
+    public function parse(\Doctrine\ORM\Query\Parser $parser): void
     {
         $parser->match(Lexer::T_IDENTIFIER);
         $parser->match(Lexer::T_OPEN_PARENTHESIS);
@@ -30,7 +30,7 @@ public function parse(\Doctrine\ORM\Query\Parser $parser)
         $parser->match(Lexer::T_CLOSE_PARENTHESIS);
     }
 
-    public function getSql(\Doctrine\ORM\Query\SqlWalker $sql_walker)
+    public function getSql(\Doctrine\ORM\Query\SqlWalker $sql_walker): string
     {
         return sprintf(
             'TIMESTAMPDIFF(%s, %s, %s)',
diff --git a/src/Query/Mysql/Truncate.php b/src/Query/Mysql/Truncate.php
index 6341ab46..5557f5bb 100644
--- a/src/Query/Mysql/Truncate.php
+++ b/src/Query/Mysql/Truncate.php
@@ -14,7 +14,7 @@ class Truncate extends FunctionNode
 
     public $patternExpression = null;
 
-    public function parse(\Doctrine\ORM\Query\Parser $parser)
+    public function parse(\Doctrine\ORM\Query\Parser $parser): void
     {
         $parser->match(Lexer::T_IDENTIFIER);
         $parser->match(Lexer::T_OPEN_PARENTHESIS);
@@ -24,7 +24,7 @@ public function parse(\Doctrine\ORM\Query\Parser $parser)
         $parser->match(Lexer::T_CLOSE_PARENTHESIS);
     }
 
-    public function getSql(\Doctrine\ORM\Query\SqlWalker $sqlWalker)
+    public function getSql(\Doctrine\ORM\Query\SqlWalker $sqlWalker): string
     {
         return 'TRUNCATE(' .
             $this->numberExpression->dispatch($sqlWalker) . ', ' .
diff --git a/src/Query/Mysql/Unhex.php b/src/Query/Mysql/Unhex.php
index 4bbf3c42..41cbf27b 100644
--- a/src/Query/Mysql/Unhex.php
+++ b/src/Query/Mysql/Unhex.php
@@ -9,12 +9,12 @@ class Unhex extends FunctionNode
 {
     public $arithmeticExpression;
 
-    public function getSql(\Doctrine\ORM\Query\SqlWalker $sqlWalker)
+    public function getSql(\Doctrine\ORM\Query\SqlWalker $sqlWalker): string
     {
         return 'UNHEX(' . $sqlWalker->walkSimpleArithmeticExpression($this->arithmeticExpression) . ')';
     }
 
-    public function parse(\Doctrine\ORM\Query\Parser $parser)
+    public function parse(\Doctrine\ORM\Query\Parser $parser): void
     {
         $parser->match(Lexer::T_IDENTIFIER);
         $parser->match(Lexer::T_OPEN_PARENTHESIS);
diff --git a/src/Query/Mysql/UnixTimestamp.php b/src/Query/Mysql/UnixTimestamp.php
index 7be1a1ce..7a49c2c8 100644
--- a/src/Query/Mysql/UnixTimestamp.php
+++ b/src/Query/Mysql/UnixTimestamp.php
@@ -13,7 +13,7 @@ class UnixTimestamp extends FunctionNode
 {
     public $date;
 
-    public function getSql(\Doctrine\ORM\Query\SqlWalker $sqlWalker)
+    public function getSql(\Doctrine\ORM\Query\SqlWalker $sqlWalker): string
     {
         return sprintf(
             'UNIX_TIMESTAMP(%s)',
@@ -21,7 +21,7 @@ public function getSql(\Doctrine\ORM\Query\SqlWalker $sqlWalker)
         );
     }
 
-    public function parse(\Doctrine\ORM\Query\Parser $parser)
+    public function parse(\Doctrine\ORM\Query\Parser $parser): void
     {
         $parser->match(Lexer::T_IDENTIFIER);
         $parser->match(Lexer::T_OPEN_PARENTHESIS);
diff --git a/src/Query/Mysql/UtcTimestamp.php b/src/Query/Mysql/UtcTimestamp.php
index 47bd48df..a32577f3 100644
--- a/src/Query/Mysql/UtcTimestamp.php
+++ b/src/Query/Mysql/UtcTimestamp.php
@@ -10,12 +10,12 @@
  */
 class UtcTimestamp extends FunctionNode
 {
-    public function getSql(\Doctrine\ORM\Query\SqlWalker $sqlWalker)
+    public function getSql(\Doctrine\ORM\Query\SqlWalker $sqlWalker): string
     {
         return 'UTC_TIMESTAMP()';
     }
 
-    public function parse(\Doctrine\ORM\Query\Parser $parser)
+    public function parse(\Doctrine\ORM\Query\Parser $parser): void
     {
         $parser->match(Lexer::T_IDENTIFIER);
         $parser->match(Lexer::T_OPEN_PARENTHESIS);
diff --git a/src/Query/Mysql/UuidShort.php b/src/Query/Mysql/UuidShort.php
index 61c91e56..41922c1a 100644
--- a/src/Query/Mysql/UuidShort.php
+++ b/src/Query/Mysql/UuidShort.php
@@ -9,12 +9,12 @@ class UuidShort extends FunctionNode
 {
     public $arithmeticExpression;
 
-    public function getSql(\Doctrine\ORM\Query\SqlWalker $sqlWalker)
+    public function getSql(\Doctrine\ORM\Query\SqlWalker $sqlWalker): string
     {
         return 'UUID_SHORT()';
     }
 
-    public function parse(\Doctrine\ORM\Query\Parser $parser)
+    public function parse(\Doctrine\ORM\Query\Parser $parser): void
     {
         $parser->match(Lexer::T_IDENTIFIER);
         $parser->match(Lexer::T_OPEN_PARENTHESIS);
diff --git a/src/Query/Mysql/Variance.php b/src/Query/Mysql/Variance.php
index 948c65b5..cadab86f 100644
--- a/src/Query/Mysql/Variance.php
+++ b/src/Query/Mysql/Variance.php
@@ -13,7 +13,7 @@ class Variance extends FunctionNode
     /** @var SimpleArithmeticExpression */
     protected $arithmeticExpression;
 
-    public function parse(Parser $parser)
+    public function parse(Parser $parser): void
     {
         $parser->match(Lexer::T_IDENTIFIER);
         $parser->match(Lexer::T_OPEN_PARENTHESIS);
@@ -23,7 +23,7 @@ public function parse(Parser $parser)
         $parser->match(Lexer::T_CLOSE_PARENTHESIS);
     }
 
-    public function getSql(SqlWalker $sqlWalker)
+    public function getSql(SqlWalker $sqlWalker): string
     {
         return sprintf('VARIANCE(%s)', $sqlWalker->walkSimpleArithmeticExpression($this->arithmeticExpression));
     }
diff --git a/src/Query/Mysql/Week.php b/src/Query/Mysql/Week.php
index a7552c1b..3efe6b4d 100644
--- a/src/Query/Mysql/Week.php
+++ b/src/Query/Mysql/Week.php
@@ -16,7 +16,7 @@ class Week extends FunctionNode
 
     public $mode;
 
-    public function getSql(\Doctrine\ORM\Query\SqlWalker $sqlWalker)
+    public function getSql(\Doctrine\ORM\Query\SqlWalker $sqlWalker): string
     {
         $sql = 'WEEK(' . $sqlWalker->walkArithmeticPrimary($this->date);
         if ($this->mode != null) {
@@ -27,7 +27,7 @@ public function getSql(\Doctrine\ORM\Query\SqlWalker $sqlWalker)
         return $sql;
     }
 
-    public function parse(\Doctrine\ORM\Query\Parser $parser)
+    public function parse(\Doctrine\ORM\Query\Parser $parser): void
     {
         $parser->match(Lexer::T_IDENTIFIER);
         $parser->match(Lexer::T_OPEN_PARENTHESIS);
diff --git a/src/Query/Mysql/WeekDay.php b/src/Query/Mysql/WeekDay.php
index be56e6af..187b2569 100644
--- a/src/Query/Mysql/WeekDay.php
+++ b/src/Query/Mysql/WeekDay.php
@@ -12,12 +12,12 @@ class WeekDay extends FunctionNode
 {
     private $date;
 
-    public function getSql(\Doctrine\ORM\Query\SqlWalker $sqlWalker)
+    public function getSql(\Doctrine\ORM\Query\SqlWalker $sqlWalker): string
     {
         return 'WEEKDAY(' . $sqlWalker->walkArithmeticPrimary($this->date) . ')';
     }
 
-    public function parse(\Doctrine\ORM\Query\Parser $parser)
+    public function parse(\Doctrine\ORM\Query\Parser $parser): void
     {
         $parser->match(Lexer::T_IDENTIFIER);
         $parser->match(Lexer::T_OPEN_PARENTHESIS);
diff --git a/src/Query/Mysql/WeekOfYear.php b/src/Query/Mysql/WeekOfYear.php
index 9b2f57c8..ce7fb57d 100644
--- a/src/Query/Mysql/WeekOfYear.php
+++ b/src/Query/Mysql/WeekOfYear.php
@@ -9,12 +9,12 @@ class WeekOfYear extends FunctionNode
 {
     private $date;
 
-    public function getSql(\Doctrine\ORM\Query\SqlWalker $sqlWalker)
+    public function getSql(\Doctrine\ORM\Query\SqlWalker $sqlWalker): string
     {
         return 'WEEKOFYEAR(' . $sqlWalker->walkArithmeticPrimary($this->date) . ')';
     }
 
-    public function parse(\Doctrine\ORM\Query\Parser $parser)
+    public function parse(\Doctrine\ORM\Query\Parser $parser): void
     {
         $parser->match(Lexer::T_IDENTIFIER);
         $parser->match(Lexer::T_OPEN_PARENTHESIS);
diff --git a/src/Query/Mysql/Year.php b/src/Query/Mysql/Year.php
index c5eb2864..f9519b88 100644
--- a/src/Query/Mysql/Year.php
+++ b/src/Query/Mysql/Year.php
@@ -12,12 +12,12 @@ class Year extends FunctionNode
 {
     public $date;
 
-    public function getSql(\Doctrine\ORM\Query\SqlWalker $sqlWalker)
+    public function getSql(\Doctrine\ORM\Query\SqlWalker $sqlWalker): string
     {
         return 'YEAR(' . $sqlWalker->walkArithmeticPrimary($this->date) . ')';
     }
 
-    public function parse(\Doctrine\ORM\Query\Parser $parser)
+    public function parse(\Doctrine\ORM\Query\Parser $parser): void
     {
         $parser->match(Lexer::T_IDENTIFIER);
         $parser->match(Lexer::T_OPEN_PARENTHESIS);
diff --git a/src/Query/Mysql/YearMonth.php b/src/Query/Mysql/YearMonth.php
index edafdaf7..e8046494 100644
--- a/src/Query/Mysql/YearMonth.php
+++ b/src/Query/Mysql/YearMonth.php
@@ -9,7 +9,7 @@ class YearMonth extends FunctionNode
 {
     public $date;
 
-    public function getSql(\Doctrine\ORM\Query\SqlWalker $sqlWalker)
+    public function getSql(\Doctrine\ORM\Query\SqlWalker $sqlWalker): string
     {
         return sprintf(
             'EXTRACT(YEAR_MONTH FROM %s)',
@@ -17,7 +17,7 @@ public function getSql(\Doctrine\ORM\Query\SqlWalker $sqlWalker)
         );
     }
 
-    public function parse(\Doctrine\ORM\Query\Parser $parser)
+    public function parse(\Doctrine\ORM\Query\Parser $parser): void
     {
         $parser->match(Lexer::T_IDENTIFIER);
         $parser->match(Lexer::T_OPEN_PARENTHESIS);
diff --git a/src/Query/Mysql/YearWeek.php b/src/Query/Mysql/YearWeek.php
index 06aa82f0..d0177a9f 100644
--- a/src/Query/Mysql/YearWeek.php
+++ b/src/Query/Mysql/YearWeek.php
@@ -14,7 +14,7 @@ class YearWeek extends FunctionNode
 
     public $mode;
 
-    public function getSql(\Doctrine\ORM\Query\SqlWalker $sqlWalker)
+    public function getSql(\Doctrine\ORM\Query\SqlWalker $sqlWalker): string
     {
         $sql = 'YEARWEEK(' . $sqlWalker->walkArithmeticPrimary($this->date);
         if ($this->mode != null) {
@@ -25,7 +25,7 @@ public function getSql(\Doctrine\ORM\Query\SqlWalker $sqlWalker)
         return $sql;
     }
 
-    public function parse(\Doctrine\ORM\Query\Parser $parser)
+    public function parse(\Doctrine\ORM\Query\Parser $parser): void
     {
         $parser->match(Lexer::T_IDENTIFIER);
         $parser->match(Lexer::T_OPEN_PARENTHESIS);
diff --git a/src/Query/MysqlWalker.php b/src/Query/MysqlWalker.php
index 1698088d..4d79b428 100644
--- a/src/Query/MysqlWalker.php
+++ b/src/Query/MysqlWalker.php
@@ -8,6 +8,8 @@ class MysqlWalker extends SqlWalker
 {
     /**
      * @inheritdoc
+     *
+     * @return array|string
      */
     public function walkSelectClause($selectClause)
     {
@@ -29,7 +31,7 @@ public function walkSelectClause($selectClause)
     /**
      * @inheritdoc
      */
-    public function walkGroupByClause($groupByClause)
+    public function walkGroupByClause($groupByClause): string
     {
         $sql = parent::walkGroupByClause($groupByClause);
 
diff --git a/src/Query/Oracle/Ceil.php b/src/Query/Oracle/Ceil.php
index 6c1d9962..a26b5529 100755
--- a/src/Query/Oracle/Ceil.php
+++ b/src/Query/Oracle/Ceil.php
@@ -12,7 +12,7 @@ class Ceil extends FunctionNode
 {
     private $number;
 
-    public function getSql(\Doctrine\ORM\Query\SqlWalker $sqlWalker)
+    public function getSql(\Doctrine\ORM\Query\SqlWalker $sqlWalker): string
     {
         return sprintf(
             'CEIL(%s)',
@@ -20,7 +20,7 @@ public function getSql(\Doctrine\ORM\Query\SqlWalker $sqlWalker)
         );
     }
 
-    public function parse(\Doctrine\ORM\Query\Parser $parser)
+    public function parse(\Doctrine\ORM\Query\Parser $parser): void
     {
         $parser->match(Lexer::T_IDENTIFIER);
         $parser->match(Lexer::T_OPEN_PARENTHESIS);
diff --git a/src/Query/Oracle/Day.php b/src/Query/Oracle/Day.php
index db27ab4f..f9e4e534 100644
--- a/src/Query/Oracle/Day.php
+++ b/src/Query/Oracle/Day.php
@@ -12,7 +12,7 @@ class Day extends FunctionNode
 {
     private $date;
 
-    public function getSql(\Doctrine\ORM\Query\SqlWalker $sqlWalker)
+    public function getSql(\Doctrine\ORM\Query\SqlWalker $sqlWalker): string
     {
         return sprintf(
             'EXTRACT(DAY FROM %s)',
@@ -20,7 +20,7 @@ public function getSql(\Doctrine\ORM\Query\SqlWalker $sqlWalker)
         );
     }
 
-    public function parse(\Doctrine\ORM\Query\Parser $parser)
+    public function parse(\Doctrine\ORM\Query\Parser $parser): void
     {
         $parser->match(Lexer::T_IDENTIFIER);
         $parser->match(Lexer::T_OPEN_PARENTHESIS);
diff --git a/src/Query/Oracle/Floor.php b/src/Query/Oracle/Floor.php
index 69b0d8ff..a05e1e83 100755
--- a/src/Query/Oracle/Floor.php
+++ b/src/Query/Oracle/Floor.php
@@ -12,7 +12,7 @@ class Floor extends FunctionNode
 {
     private $number;
 
-    public function getSql(\Doctrine\ORM\Query\SqlWalker $sqlWalker)
+    public function getSql(\Doctrine\ORM\Query\SqlWalker $sqlWalker): string
     {
         return sprintf(
             'FLOOR(%s)',
@@ -20,7 +20,7 @@ public function getSql(\Doctrine\ORM\Query\SqlWalker $sqlWalker)
         );
     }
 
-    public function parse(\Doctrine\ORM\Query\Parser $parser)
+    public function parse(\Doctrine\ORM\Query\Parser $parser): void
     {
         $parser->match(Lexer::T_IDENTIFIER);
         $parser->match(Lexer::T_OPEN_PARENTHESIS);
diff --git a/src/Query/Oracle/Hour.php b/src/Query/Oracle/Hour.php
index 77160c9e..d8cb6e65 100644
--- a/src/Query/Oracle/Hour.php
+++ b/src/Query/Oracle/Hour.php
@@ -12,7 +12,7 @@ class Hour extends FunctionNode
 {
     private $date;
 
-    public function getSql(\Doctrine\ORM\Query\SqlWalker $sqlWalker)
+    public function getSql(\Doctrine\ORM\Query\SqlWalker $sqlWalker): string
     {
         return sprintf(
             'EXTRACT(HOUR FROM %s)',
@@ -20,7 +20,7 @@ public function getSql(\Doctrine\ORM\Query\SqlWalker $sqlWalker)
         );
     }
 
-    public function parse(\Doctrine\ORM\Query\Parser $parser)
+    public function parse(\Doctrine\ORM\Query\Parser $parser): void
     {
         $parser->match(Lexer::T_IDENTIFIER);
         $parser->match(Lexer::T_OPEN_PARENTHESIS);
diff --git a/src/Query/Oracle/Listagg.php b/src/Query/Oracle/Listagg.php
index dac6406a..102c0ce2 100644
--- a/src/Query/Oracle/Listagg.php
+++ b/src/Query/Oracle/Listagg.php
@@ -37,7 +37,7 @@ class Listagg extends FunctionNode
     /**
      * @inheritdoc
      */
-    public function parse(Parser $parser)
+    public function parse(Parser $parser): void
     {
         $lexer = $parser->getLexer();
 
@@ -88,7 +88,7 @@ public function parse(Parser $parser)
     /**
      * @inheritdoc
      */
-    public function getSql(SqlWalker $sqlWalker)
+    public function getSql(SqlWalker $sqlWalker): string
     {
         $result = 'LISTAGG(' . $this->listaggField->dispatch($sqlWalker);
         if ($this->separator) {
diff --git a/src/Query/Oracle/Minute.php b/src/Query/Oracle/Minute.php
index 4579be71..a6026a51 100644
--- a/src/Query/Oracle/Minute.php
+++ b/src/Query/Oracle/Minute.php
@@ -12,7 +12,7 @@ class Minute extends FunctionNode
 {
     private $date;
 
-    public function getSql(\Doctrine\ORM\Query\SqlWalker $sqlWalker)
+    public function getSql(\Doctrine\ORM\Query\SqlWalker $sqlWalker): string
     {
         return sprintf(
             'EXTRACT(MINUTE FROM %s)',
@@ -20,7 +20,7 @@ public function getSql(\Doctrine\ORM\Query\SqlWalker $sqlWalker)
         );
     }
 
-    public function parse(\Doctrine\ORM\Query\Parser $parser)
+    public function parse(\Doctrine\ORM\Query\Parser $parser): void
     {
         $parser->match(Lexer::T_IDENTIFIER);
         $parser->match(Lexer::T_OPEN_PARENTHESIS);
diff --git a/src/Query/Oracle/Month.php b/src/Query/Oracle/Month.php
index 88356b25..6129874e 100644
--- a/src/Query/Oracle/Month.php
+++ b/src/Query/Oracle/Month.php
@@ -12,7 +12,7 @@ class Month extends FunctionNode
 {
     private $date;
 
-    public function getSql(\Doctrine\ORM\Query\SqlWalker $sqlWalker)
+    public function getSql(\Doctrine\ORM\Query\SqlWalker $sqlWalker): string
     {
         return sprintf(
             'EXTRACT(MONTH FROM %s)',
@@ -20,7 +20,7 @@ public function getSql(\Doctrine\ORM\Query\SqlWalker $sqlWalker)
         );
     }
 
-    public function parse(\Doctrine\ORM\Query\Parser $parser)
+    public function parse(\Doctrine\ORM\Query\Parser $parser): void
     {
         $parser->match(Lexer::T_IDENTIFIER);
         $parser->match(Lexer::T_OPEN_PARENTHESIS);
diff --git a/src/Query/Oracle/Nvl.php b/src/Query/Oracle/Nvl.php
index daf68e89..44702afa 100644
--- a/src/Query/Oracle/Nvl.php
+++ b/src/Query/Oracle/Nvl.php
@@ -14,7 +14,7 @@ class Nvl extends FunctionNode
 
     private $expr2;
 
-    public function getSql(\Doctrine\ORM\Query\SqlWalker $sqlWalker)
+    public function getSql(\Doctrine\ORM\Query\SqlWalker $sqlWalker): string
     {
         return sprintf(
             'NVL(%s, %s)',
@@ -23,7 +23,7 @@ public function getSql(\Doctrine\ORM\Query\SqlWalker $sqlWalker)
         );
     }
 
-    public function parse(\Doctrine\ORM\Query\Parser $parser)
+    public function parse(\Doctrine\ORM\Query\Parser $parser): void
     {
         $parser->match(Lexer::T_IDENTIFIER);
         $parser->match(Lexer::T_OPEN_PARENTHESIS);
diff --git a/src/Query/Oracle/Second.php b/src/Query/Oracle/Second.php
index d1006cea..2b27aac2 100644
--- a/src/Query/Oracle/Second.php
+++ b/src/Query/Oracle/Second.php
@@ -12,7 +12,7 @@ class Second extends FunctionNode
 {
     private $date;
 
-    public function getSql(\Doctrine\ORM\Query\SqlWalker $sqlWalker)
+    public function getSql(\Doctrine\ORM\Query\SqlWalker $sqlWalker): string
     {
         return sprintf(
             'FLOOR(EXTRACT(SECOND FROM %s))',
@@ -20,7 +20,7 @@ public function getSql(\Doctrine\ORM\Query\SqlWalker $sqlWalker)
         );
     }
 
-    public function parse(\Doctrine\ORM\Query\Parser $parser)
+    public function parse(\Doctrine\ORM\Query\Parser $parser): void
     {
         $parser->match(Lexer::T_IDENTIFIER);
         $parser->match(Lexer::T_OPEN_PARENTHESIS);
diff --git a/src/Query/Oracle/ToChar.php b/src/Query/Oracle/ToChar.php
index 4475d441..75d873b1 100755
--- a/src/Query/Oracle/ToChar.php
+++ b/src/Query/Oracle/ToChar.php
@@ -16,7 +16,7 @@ class ToChar extends FunctionNode
 
     private $nls = null;
 
-    public function getSql(\Doctrine\ORM\Query\SqlWalker $sqlWalker)
+    public function getSql(\Doctrine\ORM\Query\SqlWalker $sqlWalker): string
     {
         if ($this->nls) {
             return sprintf(
@@ -34,7 +34,7 @@ public function getSql(\Doctrine\ORM\Query\SqlWalker $sqlWalker)
         );
     }
 
-    public function parse(\Doctrine\ORM\Query\Parser $parser)
+    public function parse(\Doctrine\ORM\Query\Parser $parser): void
     {
         $lexer = $parser->getLexer();
 
diff --git a/src/Query/Oracle/ToDate.php b/src/Query/Oracle/ToDate.php
index 8632789f..9acc84c8 100644
--- a/src/Query/Oracle/ToDate.php
+++ b/src/Query/Oracle/ToDate.php
@@ -14,7 +14,7 @@ class ToDate extends FunctionNode
 
     private $fmt;
 
-    public function getSql(\Doctrine\ORM\Query\SqlWalker $sqlWalker)
+    public function getSql(\Doctrine\ORM\Query\SqlWalker $sqlWalker): string
     {
         return sprintf(
             'TO_DATE(%s, %s)',
@@ -23,7 +23,7 @@ public function getSql(\Doctrine\ORM\Query\SqlWalker $sqlWalker)
         );
     }
 
-    public function parse(\Doctrine\ORM\Query\Parser $parser)
+    public function parse(\Doctrine\ORM\Query\Parser $parser): void
     {
         $parser->match(Lexer::T_IDENTIFIER);
         $parser->match(Lexer::T_OPEN_PARENTHESIS);
diff --git a/src/Query/Oracle/Trunc.php b/src/Query/Oracle/Trunc.php
index 629b1c46..56650a59 100755
--- a/src/Query/Oracle/Trunc.php
+++ b/src/Query/Oracle/Trunc.php
@@ -21,7 +21,7 @@ class Trunc extends FunctionNode
      */
     private $fmt;
 
-    public function getSql(\Doctrine\ORM\Query\SqlWalker $sqlWalker)
+    public function getSql(\Doctrine\ORM\Query\SqlWalker $sqlWalker): string
     {
         if ($this->fmt) {
             return sprintf(
@@ -37,7 +37,7 @@ public function getSql(\Doctrine\ORM\Query\SqlWalker $sqlWalker)
         );
     }
 
-    public function parse(\Doctrine\ORM\Query\Parser $parser)
+    public function parse(\Doctrine\ORM\Query\Parser $parser): void
     {
         $lexer = $parser->getLexer();
 
diff --git a/src/Query/Oracle/Year.php b/src/Query/Oracle/Year.php
index 1985904f..7dc76e0f 100644
--- a/src/Query/Oracle/Year.php
+++ b/src/Query/Oracle/Year.php
@@ -12,7 +12,7 @@ class Year extends FunctionNode
 {
     private $date;
 
-    public function getSql(\Doctrine\ORM\Query\SqlWalker $sqlWalker)
+    public function getSql(\Doctrine\ORM\Query\SqlWalker $sqlWalker): string
     {
         return sprintf(
             'EXTRACT(YEAR FROM %s)',
@@ -20,7 +20,7 @@ public function getSql(\Doctrine\ORM\Query\SqlWalker $sqlWalker)
         );
     }
 
-    public function parse(\Doctrine\ORM\Query\Parser $parser)
+    public function parse(\Doctrine\ORM\Query\Parser $parser): void
     {
         $parser->match(Lexer::T_IDENTIFIER);
         $parser->match(Lexer::T_OPEN_PARENTHESIS);
diff --git a/src/Query/Postgresql/AtTimeZoneFunction.php b/src/Query/Postgresql/AtTimeZoneFunction.php
index 92594aff..c9ee23f9 100644
--- a/src/Query/Postgresql/AtTimeZoneFunction.php
+++ b/src/Query/Postgresql/AtTimeZoneFunction.php
@@ -16,7 +16,7 @@ class AtTimeZoneFunction extends FunctionNode
 
     public $timezoneExpression = null;
 
-    public function parse(Parser $parser)
+    public function parse(Parser $parser): void
     {
         $parser->match(Lexer::T_IDENTIFIER);
         $parser->match(Lexer::T_OPEN_PARENTHESIS);
@@ -26,7 +26,7 @@ public function parse(Parser $parser)
         $parser->match(Lexer::T_CLOSE_PARENTHESIS);
     }
 
-    public function getSql(SqlWalker $sqlWalker)
+    public function getSql(SqlWalker $sqlWalker): string
     {
         return sprintf(
             '%s AT TIME ZONE %s',
diff --git a/src/Query/Postgresql/CountFilterFunction.php b/src/Query/Postgresql/CountFilterFunction.php
index 67930565..1a562a78 100644
--- a/src/Query/Postgresql/CountFilterFunction.php
+++ b/src/Query/Postgresql/CountFilterFunction.php
@@ -16,7 +16,7 @@ class CountFilterFunction extends FunctionNode
 
     public $whereExpression = null;
 
-    public function parse(Parser $parser)
+    public function parse(Parser $parser): void
     {
         $parser->match(Lexer::T_IDENTIFIER);
         $parser->match(Lexer::T_OPEN_PARENTHESIS);
@@ -26,7 +26,7 @@ public function parse(Parser $parser)
         $parser->match(Lexer::T_CLOSE_PARENTHESIS);
     }
 
-    public function getSql(SqlWalker $sqlWalker)
+    public function getSql(SqlWalker $sqlWalker): string
     {
         return sprintf(
             'COUNT(%s) FILTER(%s)',
diff --git a/src/Query/Postgresql/Date.php b/src/Query/Postgresql/Date.php
index d5993118..d847862b 100644
--- a/src/Query/Postgresql/Date.php
+++ b/src/Query/Postgresql/Date.php
@@ -9,12 +9,12 @@ class Date extends FunctionNode
 {
     public $date;
 
-    public function getSql(\Doctrine\ORM\Query\SqlWalker $sqlWalker)
+    public function getSql(\Doctrine\ORM\Query\SqlWalker $sqlWalker): string
     {
         return 'DATE(' . $sqlWalker->walkArithmeticPrimary($this->date) . ')';
     }
 
-    public function parse(\Doctrine\ORM\Query\Parser $parser)
+    public function parse(\Doctrine\ORM\Query\Parser $parser): void
     {
         $parser->match(Lexer::T_IDENTIFIER);
         $parser->match(Lexer::T_OPEN_PARENTHESIS);
diff --git a/src/Query/Postgresql/DateFormat.php b/src/Query/Postgresql/DateFormat.php
index 5bcd419e..7dd6a67a 100644
--- a/src/Query/Postgresql/DateFormat.php
+++ b/src/Query/Postgresql/DateFormat.php
@@ -14,7 +14,7 @@ class DateFormat extends FunctionNode
 
     public $patternExpression = null;
 
-    public function parse(\Doctrine\ORM\Query\Parser $parser)
+    public function parse(\Doctrine\ORM\Query\Parser $parser): void
     {
         $parser->match(Lexer::T_IDENTIFIER);
         $parser->match(Lexer::T_OPEN_PARENTHESIS);
@@ -24,7 +24,7 @@ public function parse(\Doctrine\ORM\Query\Parser $parser)
         $parser->match(Lexer::T_CLOSE_PARENTHESIS);
     }
 
-    public function getSql(\Doctrine\ORM\Query\SqlWalker $sqlWalker)
+    public function getSql(\Doctrine\ORM\Query\SqlWalker $sqlWalker): string
     {
         return 'TO_CHAR(' .
             $this->dateExpression->dispatch($sqlWalker) . ', ' .
diff --git a/src/Query/Postgresql/DatePart.php b/src/Query/Postgresql/DatePart.php
index 2f7b9ebd..faba0a80 100644
--- a/src/Query/Postgresql/DatePart.php
+++ b/src/Query/Postgresql/DatePart.php
@@ -13,10 +13,10 @@
 class DatePart extends FunctionNode
 {
     public $dateString = null;
-    
+
     public $dateFormat = null;
 
-    public function parse(Parser $parser)
+    public function parse(Parser $parser): void
     {
         $parser->match(Lexer::T_IDENTIFIER);
         $parser->match(Lexer::T_OPEN_PARENTHESIS);
@@ -26,7 +26,7 @@ public function parse(Parser $parser)
         $parser->match(Lexer::T_CLOSE_PARENTHESIS);
     }
 
-    public function getSql(SqlWalker $sqlWalker)
+    public function getSql(SqlWalker $sqlWalker): string
     {
         return 'DATE_PART(' .
             $this->dateString->dispatch($sqlWalker) . ', ' .
diff --git a/src/Query/Postgresql/DateTrunc.php b/src/Query/Postgresql/DateTrunc.php
index 7aef29a2..9ceefbf8 100644
--- a/src/Query/Postgresql/DateTrunc.php
+++ b/src/Query/Postgresql/DateTrunc.php
@@ -13,7 +13,7 @@ class DateTrunc extends FunctionNode
 
     public $fieldTimestamp = null;
 
-    public function parse(Parser $parser)
+    public function parse(Parser $parser): void
     {
         $parser->match(Lexer::T_IDENTIFIER);
         $parser->match(Lexer::T_OPEN_PARENTHESIS);
@@ -23,7 +23,7 @@ public function parse(Parser $parser)
         $parser->match(Lexer::T_CLOSE_PARENTHESIS);
     }
 
-    public function getSql(SqlWalker $sqlWalker)
+    public function getSql(SqlWalker $sqlWalker): string
     {
         return sprintf(
             'DATE_TRUNC(%s, %s)',
diff --git a/src/Query/Postgresql/Day.php b/src/Query/Postgresql/Day.php
index 045cb4d2..57d4bcd5 100644
--- a/src/Query/Postgresql/Day.php
+++ b/src/Query/Postgresql/Day.php
@@ -9,7 +9,7 @@ class Day extends FunctionNode
 {
     private $date;
 
-    public function getSql(\Doctrine\ORM\Query\SqlWalker $sqlWalker)
+    public function getSql(\Doctrine\ORM\Query\SqlWalker $sqlWalker): string
     {
         return sprintf(
             'EXTRACT(DAY FROM %s)',
@@ -17,7 +17,7 @@ public function getSql(\Doctrine\ORM\Query\SqlWalker $sqlWalker)
         );
     }
 
-    public function parse(\Doctrine\ORM\Query\Parser $parser)
+    public function parse(\Doctrine\ORM\Query\Parser $parser): void
     {
         $parser->match(Lexer::T_IDENTIFIER);
         $parser->match(Lexer::T_OPEN_PARENTHESIS);
diff --git a/src/Query/Postgresql/Greatest.php b/src/Query/Postgresql/Greatest.php
index c2a6e183..d0850c2b 100644
--- a/src/Query/Postgresql/Greatest.php
+++ b/src/Query/Postgresql/Greatest.php
@@ -21,7 +21,7 @@ class Greatest extends FunctionNode
     /**
      * @param Parser $parser
      */
-    public function parse(Parser $parser)
+    public function parse(Parser $parser): void
     {
         $parser->match(Lexer::T_IDENTIFIER);
         $parser->match(Lexer::T_OPEN_PARENTHESIS);
@@ -41,7 +41,7 @@ public function parse(Parser $parser)
      * @param SqlWalker $sqlWalker
      * @return string
      */
-    public function getSql(SqlWalker $sqlWalker)
+    public function getSql(SqlWalker $sqlWalker): string
     {
         $query = 'GREATEST(';
 
diff --git a/src/Query/Postgresql/Hour.php b/src/Query/Postgresql/Hour.php
index d05af9df..27b37707 100644
--- a/src/Query/Postgresql/Hour.php
+++ b/src/Query/Postgresql/Hour.php
@@ -9,7 +9,7 @@ class Hour extends FunctionNode
 {
     private $date;
 
-    public function getSql(\Doctrine\ORM\Query\SqlWalker $sqlWalker)
+    public function getSql(\Doctrine\ORM\Query\SqlWalker $sqlWalker): string
     {
         return sprintf(
             'EXTRACT(HOUR FROM %s)',
@@ -17,7 +17,7 @@ public function getSql(\Doctrine\ORM\Query\SqlWalker $sqlWalker)
         );
     }
 
-    public function parse(\Doctrine\ORM\Query\Parser $parser)
+    public function parse(\Doctrine\ORM\Query\Parser $parser): void
     {
         $parser->match(Lexer::T_IDENTIFIER);
         $parser->match(Lexer::T_OPEN_PARENTHESIS);
diff --git a/src/Query/Postgresql/Least.php b/src/Query/Postgresql/Least.php
index ad05b5bc..ef91c94e 100644
--- a/src/Query/Postgresql/Least.php
+++ b/src/Query/Postgresql/Least.php
@@ -20,7 +20,7 @@ class Least extends FunctionNode
     /**
      * @param Parser $parser
      */
-    public function parse(Parser $parser)
+    public function parse(Parser $parser): void
     {
         $parser->match(Lexer::T_IDENTIFIER);
         $parser->match(Lexer::T_OPEN_PARENTHESIS);
@@ -40,7 +40,7 @@ public function parse(Parser $parser)
      * @param SqlWalker $sqlWalker
      * @return string
      */
-    public function getSql(SqlWalker $sqlWalker)
+    public function getSql(SqlWalker $sqlWalker): string
     {
         $query = 'LEAST(';
 
diff --git a/src/Query/Postgresql/Minute.php b/src/Query/Postgresql/Minute.php
index c4832910..2464dcdf 100644
--- a/src/Query/Postgresql/Minute.php
+++ b/src/Query/Postgresql/Minute.php
@@ -9,7 +9,7 @@ class Minute extends FunctionNode
 {
     private $date;
 
-    public function getSql(\Doctrine\ORM\Query\SqlWalker $sqlWalker)
+    public function getSql(\Doctrine\ORM\Query\SqlWalker $sqlWalker): string
     {
         return sprintf(
             'EXTRACT(MINUTE FROM %s)',
@@ -17,7 +17,7 @@ public function getSql(\Doctrine\ORM\Query\SqlWalker $sqlWalker)
         );
     }
 
-    public function parse(\Doctrine\ORM\Query\Parser $parser)
+    public function parse(\Doctrine\ORM\Query\Parser $parser): void
     {
         $parser->match(Lexer::T_IDENTIFIER);
         $parser->match(Lexer::T_OPEN_PARENTHESIS);
diff --git a/src/Query/Postgresql/Month.php b/src/Query/Postgresql/Month.php
index 0ad92318..3437d658 100644
--- a/src/Query/Postgresql/Month.php
+++ b/src/Query/Postgresql/Month.php
@@ -9,7 +9,7 @@ class Month extends FunctionNode
 {
     private $date;
 
-    public function getSql(\Doctrine\ORM\Query\SqlWalker $sqlWalker)
+    public function getSql(\Doctrine\ORM\Query\SqlWalker $sqlWalker): string
     {
         return sprintf(
             'EXTRACT(MONTH FROM %s)',
@@ -17,7 +17,7 @@ public function getSql(\Doctrine\ORM\Query\SqlWalker $sqlWalker)
         );
     }
 
-    public function parse(\Doctrine\ORM\Query\Parser $parser)
+    public function parse(\Doctrine\ORM\Query\Parser $parser): void
     {
         $parser->match(Lexer::T_IDENTIFIER);
         $parser->match(Lexer::T_OPEN_PARENTHESIS);
diff --git a/src/Query/Postgresql/RegexpReplace.php b/src/Query/Postgresql/RegexpReplace.php
index cf2ed8fe..a9dfe85b 100644
--- a/src/Query/Postgresql/RegexpReplace.php
+++ b/src/Query/Postgresql/RegexpReplace.php
@@ -17,12 +17,12 @@ class RegexpReplace extends FunctionNode
 
     private $replace;
 
-    public function getSql(\Doctrine\ORM\Query\SqlWalker $sqlWalker)
+    public function getSql(\Doctrine\ORM\Query\SqlWalker $sqlWalker): string
     {
         return 'REGEXP_REPLACE('.$this->string->dispatch($sqlWalker).', '.$this->search->dispatch($sqlWalker).', '.$this->replace->dispatch($sqlWalker).')';
     }
 
-    public function parse(\Doctrine\ORM\Query\Parser $parser)
+    public function parse(\Doctrine\ORM\Query\Parser $parser): void
     {
         $parser->match(Lexer::T_IDENTIFIER);
         $parser->match(Lexer::T_OPEN_PARENTHESIS);
diff --git a/src/Query/Postgresql/Second.php b/src/Query/Postgresql/Second.php
index 604ed37b..4bd64232 100644
--- a/src/Query/Postgresql/Second.php
+++ b/src/Query/Postgresql/Second.php
@@ -9,7 +9,7 @@ class Second extends FunctionNode
 {
     private $date;
 
-    public function getSql(\Doctrine\ORM\Query\SqlWalker $sqlWalker)
+    public function getSql(\Doctrine\ORM\Query\SqlWalker $sqlWalker): string
     {
         return sprintf(
             'FLOOR(EXTRACT(SECOND FROM %s))',
@@ -17,7 +17,7 @@ public function getSql(\Doctrine\ORM\Query\SqlWalker $sqlWalker)
         );
     }
 
-    public function parse(\Doctrine\ORM\Query\Parser $parser)
+    public function parse(\Doctrine\ORM\Query\Parser $parser): void
     {
         $parser->match(Lexer::T_IDENTIFIER);
         $parser->match(Lexer::T_OPEN_PARENTHESIS);
diff --git a/src/Query/Postgresql/StrToDate.php b/src/Query/Postgresql/StrToDate.php
index cb2ffed1..55d57121 100644
--- a/src/Query/Postgresql/StrToDate.php
+++ b/src/Query/Postgresql/StrToDate.php
@@ -11,7 +11,7 @@ class StrToDate extends FunctionNode
 
     public $dateFormat = null;
 
-    public function parse(\Doctrine\ORM\Query\Parser $parser)
+    public function parse(\Doctrine\ORM\Query\Parser $parser): void
     {
         $parser->match(Lexer::T_IDENTIFIER);
         $parser->match(Lexer::T_OPEN_PARENTHESIS);
@@ -21,7 +21,7 @@ public function parse(\Doctrine\ORM\Query\Parser $parser)
         $parser->match(Lexer::T_CLOSE_PARENTHESIS);
     }
 
-    public function getSql(\Doctrine\ORM\Query\SqlWalker $sqlWalker)
+    public function getSql(\Doctrine\ORM\Query\SqlWalker $sqlWalker): string
     {
         return 'TO_DATE(' .
             $this->dateString->dispatch($sqlWalker) . ', ' .
diff --git a/src/Query/Postgresql/StringAgg.php b/src/Query/Postgresql/StringAgg.php
index e5905f7d..67b6688b 100644
--- a/src/Query/Postgresql/StringAgg.php
+++ b/src/Query/Postgresql/StringAgg.php
@@ -22,7 +22,7 @@ class StringAgg extends FunctionNode
 
     private $isDistinct = false;
 
-    public function parse(Parser $parser)
+    public function parse(Parser $parser): void
     {
         $parser->match(Lexer::T_IDENTIFIER);
         $parser->match(Lexer::T_OPEN_PARENTHESIS);
@@ -45,7 +45,7 @@ public function parse(Parser $parser)
         $parser->match(Lexer::T_CLOSE_PARENTHESIS);
     }
 
-    public function getSql(SqlWalker $sqlWalker)
+    public function getSql(SqlWalker $sqlWalker): string
     {
         return \sprintf(
             'string_agg(%s%s, %s%s)',
diff --git a/src/Query/Postgresql/Year.php b/src/Query/Postgresql/Year.php
index ceec24c9..4c9d2328 100644
--- a/src/Query/Postgresql/Year.php
+++ b/src/Query/Postgresql/Year.php
@@ -9,7 +9,7 @@ class Year extends FunctionNode
 {
     private $date;
 
-    public function getSql(\Doctrine\ORM\Query\SqlWalker $sqlWalker)
+    public function getSql(\Doctrine\ORM\Query\SqlWalker $sqlWalker): string
     {
         return sprintf(
             'EXTRACT(YEAR FROM %s)',
@@ -17,7 +17,7 @@ public function getSql(\Doctrine\ORM\Query\SqlWalker $sqlWalker)
         );
     }
 
-    public function parse(\Doctrine\ORM\Query\Parser $parser)
+    public function parse(\Doctrine\ORM\Query\Parser $parser): void
     {
         $parser->match(Lexer::T_IDENTIFIER);
         $parser->match(Lexer::T_OPEN_PARENTHESIS);
diff --git a/src/Query/SortableNullsWalker.php b/src/Query/SortableNullsWalker.php
index 648387de..34cdc021 100644
--- a/src/Query/SortableNullsWalker.php
+++ b/src/Query/SortableNullsWalker.php
@@ -28,10 +28,14 @@
  */
 class SortableNullsWalker extends Query\SqlWalker
 {
-    const NULLS_FIRST = 'NULLS FIRST';
+    public const NULLS_FIRST = 'NULLS FIRST';
 
-    const NULLS_LAST = 'NULLS LAST';
+    public const NULLS_LAST = 'NULLS LAST';
 
+    /**
+     * @param $orderByItem
+     * @return array|string
+     */
     public function walkOrderByItem($orderByItem)
     {
         $sql = parent::walkOrderByItem($orderByItem);
diff --git a/src/Query/Sqlite/AbstractStrfTime.php b/src/Query/Sqlite/AbstractStrfTime.php
index 4dffe58a..8fde4ed9 100644
--- a/src/Query/Sqlite/AbstractStrfTime.php
+++ b/src/Query/Sqlite/AbstractStrfTime.php
@@ -12,7 +12,7 @@ abstract class AbstractStrfTime extends FunctionNode
 {
     public $date;
 
-    public function getSql(\Doctrine\ORM\Query\SqlWalker $sqlWalker)
+    public function getSql(\Doctrine\ORM\Query\SqlWalker $sqlWalker): string
     {
         return "STRFTIME('"
                 . $this->getFormat()
@@ -21,7 +21,7 @@ public function getSql(\Doctrine\ORM\Query\SqlWalker $sqlWalker)
             . ')';
     }
 
-    public function parse(\Doctrine\ORM\Query\Parser $parser)
+    public function parse(\Doctrine\ORM\Query\Parser $parser): void
     {
         $parser->match(Lexer::T_IDENTIFIER);
         $parser->match(Lexer::T_OPEN_PARENTHESIS);
@@ -31,5 +31,5 @@ public function parse(\Doctrine\ORM\Query\Parser $parser)
         $parser->match(Lexer::T_CLOSE_PARENTHESIS);
     }
 
-    abstract protected function getFormat();
+    abstract protected function getFormat(): string;
 }
diff --git a/src/Query/Sqlite/ConcatWs.php b/src/Query/Sqlite/ConcatWs.php
index 06b7e973..02229c7b 100644
--- a/src/Query/Sqlite/ConcatWs.php
+++ b/src/Query/Sqlite/ConcatWs.php
@@ -14,7 +14,7 @@ class ConcatWs extends FunctionNode
 
     private $notEmpty = false;
 
-    public function parse(\Doctrine\ORM\Query\Parser $parser)
+    public function parse(\Doctrine\ORM\Query\Parser $parser): void
     {
         $parser->match(Lexer::T_IDENTIFIER);
         $parser->match(Lexer::T_OPEN_PARENTHESIS);
@@ -53,7 +53,7 @@ public function parse(\Doctrine\ORM\Query\Parser $parser)
         $parser->match(Lexer::T_CLOSE_PARENTHESIS);
     }
 
-    public function getSql(\Doctrine\ORM\Query\SqlWalker $sqlWalker)
+    public function getSql(\Doctrine\ORM\Query\SqlWalker $sqlWalker): string
     {
         $separator = $this->values[0]->simpleArithmeticExpression->value;
 
diff --git a/src/Query/Sqlite/Date.php b/src/Query/Sqlite/Date.php
index 24082225..f6173545 100644
--- a/src/Query/Sqlite/Date.php
+++ b/src/Query/Sqlite/Date.php
@@ -7,7 +7,7 @@
  */
 class Date extends AbstractStrfTime
 {
-    protected function getFormat()
+    protected function getFormat(): string
     {
         return '%Y-%m-%d';
     }
diff --git a/src/Query/Sqlite/DateFormat.php b/src/Query/Sqlite/DateFormat.php
index df458290..8ed2e81e 100644
--- a/src/Query/Sqlite/DateFormat.php
+++ b/src/Query/Sqlite/DateFormat.php
@@ -22,7 +22,7 @@ class DateFormat extends FunctionNode
      * @param \Doctrine\ORM\Query\SqlWalker $sqlWalker
      * @return string
      */
-    public function getSql(\Doctrine\ORM\Query\SqlWalker $sqlWalker)
+    public function getSql(\Doctrine\ORM\Query\SqlWalker $sqlWalker): string
     {
         return 'STRFTIME('
             . $sqlWalker->walkArithmeticPrimary($this->format)
@@ -34,7 +34,7 @@ public function getSql(\Doctrine\ORM\Query\SqlWalker $sqlWalker)
     /**
      * @param \Doctrine\ORM\Query\Parser $parser
      */
-    public function parse(\Doctrine\ORM\Query\Parser $parser)
+    public function parse(\Doctrine\ORM\Query\Parser $parser): void
     {
         $parser->match(Lexer::T_IDENTIFIER);
         $parser->match(Lexer::T_OPEN_PARENTHESIS);
@@ -49,7 +49,7 @@ public function parse(\Doctrine\ORM\Query\Parser $parser)
      * @param ArithmeticExpression $expr
      * @return ArithmeticExpression
      */
-    private function convertFormat(ArithmeticExpression $expr)
+    private function convertFormat(ArithmeticExpression $expr): ArithmeticExpression
     {
         // when using bind variables there is no value component.
         if (empty($expr->simpleArithmeticExpression->value)) {
diff --git a/src/Query/Sqlite/Day.php b/src/Query/Sqlite/Day.php
index 0b2f53b6..0c316829 100644
--- a/src/Query/Sqlite/Day.php
+++ b/src/Query/Sqlite/Day.php
@@ -7,7 +7,7 @@
  */
 class Day extends NumberFromStrfTime
 {
-    protected function getFormat()
+    protected function getFormat(): string
     {
         return '%d';
     }
diff --git a/src/Query/Sqlite/Greatest.php b/src/Query/Sqlite/Greatest.php
index cd36996e..d7b983e6 100644
--- a/src/Query/Sqlite/Greatest.php
+++ b/src/Query/Sqlite/Greatest.php
@@ -20,7 +20,7 @@ class Greatest extends FunctionNode
     /**
      * @param Parser $parser
      */
-    public function parse(Parser $parser)
+    public function parse(Parser $parser): void
     {
         $parser->match(Lexer::T_IDENTIFIER);
         $parser->match(Lexer::T_OPEN_PARENTHESIS);
@@ -40,7 +40,7 @@ public function parse(Parser $parser)
      * @param SqlWalker $sqlWalker
      * @return string
      */
-    public function getSql(SqlWalker $sqlWalker)
+    public function getSql(SqlWalker $sqlWalker): string
     {
         $query = 'MAX(';
 
diff --git a/src/Query/Sqlite/Hour.php b/src/Query/Sqlite/Hour.php
index 944c13bb..230d07e1 100644
--- a/src/Query/Sqlite/Hour.php
+++ b/src/Query/Sqlite/Hour.php
@@ -7,7 +7,7 @@
  */
 class Hour extends NumberFromStrfTime
 {
-    protected function getFormat()
+    protected function getFormat(): string
     {
         return '%H';
     }
diff --git a/src/Query/Sqlite/IfElse.php b/src/Query/Sqlite/IfElse.php
index 1534fc7c..f54f49c6 100644
--- a/src/Query/Sqlite/IfElse.php
+++ b/src/Query/Sqlite/IfElse.php
@@ -12,7 +12,7 @@ class IfElse extends FunctionNode
 {
     private $expr = [];
 
-    public function parse(\Doctrine\ORM\Query\Parser $parser)
+    public function parse(\Doctrine\ORM\Query\Parser $parser): void
     {
         $parser->match(Lexer::T_IDENTIFIER);
         $parser->match(Lexer::T_OPEN_PARENTHESIS);
@@ -26,7 +26,7 @@ public function parse(\Doctrine\ORM\Query\Parser $parser)
         $parser->match(Lexer::T_CLOSE_PARENTHESIS);
     }
 
-    public function getSql(\Doctrine\ORM\Query\SqlWalker $sqlWalker)
+    public function getSql(\Doctrine\ORM\Query\SqlWalker $sqlWalker): string
     {
         return sprintf(
             'CASE WHEN %s THEN %s ELSE %s END',
diff --git a/src/Query/Sqlite/IfNull.php b/src/Query/Sqlite/IfNull.php
index 57f3d3ad..77f26c43 100644
--- a/src/Query/Sqlite/IfNull.php
+++ b/src/Query/Sqlite/IfNull.php
@@ -14,7 +14,7 @@ class IfNull extends FunctionNode
 
     private $expr2;
 
-    public function parse(\Doctrine\ORM\Query\Parser $parser)
+    public function parse(\Doctrine\ORM\Query\Parser $parser): void
     {
         $parser->match(Lexer::T_IDENTIFIER);
         $parser->match(Lexer::T_OPEN_PARENTHESIS);
@@ -24,7 +24,7 @@ public function parse(\Doctrine\ORM\Query\Parser $parser)
         $parser->match(Lexer::T_CLOSE_PARENTHESIS);
     }
 
-    public function getSql(\Doctrine\ORM\Query\SqlWalker $sqlWalker)
+    public function getSql(\Doctrine\ORM\Query\SqlWalker $sqlWalker): string
     {
         return 'IFNULL('
             . $sqlWalker->walkArithmeticPrimary($this->expr1)
diff --git a/src/Query/Sqlite/JulianDay.php b/src/Query/Sqlite/JulianDay.php
index 46e0ef45..4341b732 100644
--- a/src/Query/Sqlite/JulianDay.php
+++ b/src/Query/Sqlite/JulianDay.php
@@ -7,7 +7,7 @@
  */
 class JulianDay extends NumberFromStrfTime
 {
-    protected function getFormat()
+    protected function getFormat(): string
     {
         return '%J';
     }
diff --git a/src/Query/Sqlite/Least.php b/src/Query/Sqlite/Least.php
index 63e31abc..a1c2edc2 100644
--- a/src/Query/Sqlite/Least.php
+++ b/src/Query/Sqlite/Least.php
@@ -19,7 +19,7 @@ class Least extends FunctionNode
     /**
      * @param Parser $parser
      */
-    public function parse(Parser $parser)
+    public function parse(Parser $parser): void
     {
         $parser->match(Lexer::T_IDENTIFIER);
         $parser->match(Lexer::T_OPEN_PARENTHESIS);
@@ -39,7 +39,7 @@ public function parse(Parser $parser)
      * @param SqlWalker $sqlWalker
      * @return string
      */
-    public function getSql(SqlWalker $sqlWalker)
+    public function getSql(SqlWalker $sqlWalker): string
     {
         $query = 'MIN(';
 
diff --git a/src/Query/Sqlite/Minute.php b/src/Query/Sqlite/Minute.php
index 5db0ef67..c787b743 100644
--- a/src/Query/Sqlite/Minute.php
+++ b/src/Query/Sqlite/Minute.php
@@ -7,7 +7,7 @@
  */
 class Minute extends NumberFromStrfTime
 {
-    protected function getFormat()
+    protected function getFormat(): string
     {
         return '%M';
     }
diff --git a/src/Query/Sqlite/Month.php b/src/Query/Sqlite/Month.php
index d036683d..49dfcbb7 100644
--- a/src/Query/Sqlite/Month.php
+++ b/src/Query/Sqlite/Month.php
@@ -7,7 +7,7 @@
  */
 class Month extends NumberFromStrfTime
 {
-    protected function getFormat()
+    protected function getFormat(): string
     {
         return '%m';
     }
diff --git a/src/Query/Sqlite/NumberFromStrfTime.php b/src/Query/Sqlite/NumberFromStrfTime.php
index 7eed2fcc..d071b72b 100644
--- a/src/Query/Sqlite/NumberFromStrfTime.php
+++ b/src/Query/Sqlite/NumberFromStrfTime.php
@@ -4,7 +4,7 @@
 
 abstract class NumberFromStrfTime extends AbstractStrfTime
 {
-    public function getSql(\Doctrine\ORM\Query\SqlWalker $sqlWalker)
+    public function getSql(\Doctrine\ORM\Query\SqlWalker $sqlWalker): string
     {
         return "CAST(STRFTIME('"
                 . $this->getFormat()
diff --git a/src/Query/Sqlite/Random.php b/src/Query/Sqlite/Random.php
index 896397d7..b13cfdb4 100644
--- a/src/Query/Sqlite/Random.php
+++ b/src/Query/Sqlite/Random.php
@@ -7,12 +7,12 @@
 
 class Random extends FunctionNode
 {
-    public function getSql(\Doctrine\ORM\Query\SqlWalker $sqlWalker)
+    public function getSql(\Doctrine\ORM\Query\SqlWalker $sqlWalker): string
     {
         return 'RANDOM()';
     }
 
-    public function parse(\Doctrine\ORM\Query\Parser $parser)
+    public function parse(\Doctrine\ORM\Query\Parser $parser): void
     {
         $parser->match(Lexer::T_IDENTIFIER);
         $parser->match(Lexer::T_OPEN_PARENTHESIS);
diff --git a/src/Query/Sqlite/Replace.php b/src/Query/Sqlite/Replace.php
index 872a625a..6b00f1c6 100644
--- a/src/Query/Sqlite/Replace.php
+++ b/src/Query/Sqlite/Replace.php
@@ -16,7 +16,7 @@ class Replace extends FunctionNode
 
     public $subject = null;
 
-    public function parse(\Doctrine\ORM\Query\Parser $parser)
+    public function parse(\Doctrine\ORM\Query\Parser $parser): void
     {
         $parser->match(Lexer::T_IDENTIFIER);
         $parser->match(Lexer::T_OPEN_PARENTHESIS);
@@ -28,7 +28,7 @@ public function parse(\Doctrine\ORM\Query\Parser $parser)
         $parser->match(Lexer::T_CLOSE_PARENTHESIS);
     }
 
-    public function getSql(\Doctrine\ORM\Query\SqlWalker $sqlWalker)
+    public function getSql(\Doctrine\ORM\Query\SqlWalker $sqlWalker): string
     {
         return 'REPLACE(' .
             $this->subject->dispatch($sqlWalker) . ', ' .
diff --git a/src/Query/Sqlite/Round.php b/src/Query/Sqlite/Round.php
index 9b5465fa..605fca45 100644
--- a/src/Query/Sqlite/Round.php
+++ b/src/Query/Sqlite/Round.php
@@ -14,7 +14,7 @@ class Round extends FunctionNode
 
     private $secondExpression = null;
 
-    public function parse(\Doctrine\ORM\Query\Parser $parser)
+    public function parse(\Doctrine\ORM\Query\Parser $parser): void
     {
         $lexer = $parser->getLexer();
         $parser->match(Lexer::T_IDENTIFIER);
@@ -30,7 +30,7 @@ public function parse(\Doctrine\ORM\Query\Parser $parser)
         $parser->match(Lexer::T_CLOSE_PARENTHESIS);
     }
 
-    public function getSql(\Doctrine\ORM\Query\SqlWalker $sqlWalker)
+    public function getSql(\Doctrine\ORM\Query\SqlWalker $sqlWalker): string
     {
         // use second parameter if parsed
         if (null !== $this->secondExpression) {
diff --git a/src/Query/Sqlite/Second.php b/src/Query/Sqlite/Second.php
index 5009b8a0..46d0cb98 100644
--- a/src/Query/Sqlite/Second.php
+++ b/src/Query/Sqlite/Second.php
@@ -4,7 +4,7 @@
 
 class Second extends NumberFromStrfTime
 {
-    protected function getFormat()
+    protected function getFormat(): string
     {
         return '%S';
     }
diff --git a/src/Query/Sqlite/StrfTime.php b/src/Query/Sqlite/StrfTime.php
index db33dd80..b329632d 100644
--- a/src/Query/Sqlite/StrfTime.php
+++ b/src/Query/Sqlite/StrfTime.php
@@ -22,7 +22,7 @@ class StrfTime extends FunctionNode
      * @throws \Doctrine\ORM\Query\QueryException
      * @return string
      */
-    public function getSql(SqlWalker $sqlWalker)
+    public function getSql(SqlWalker $sqlWalker): string
     {
         return 'strftime('
         . $sqlWalker->walkLiteral($this->formatter)
@@ -31,7 +31,7 @@ public function getSql(SqlWalker $sqlWalker)
         . ')';
     }
 
-    public function parse(Parser $parser)
+    public function parse(Parser $parser): void
     {
         $parser->match(Lexer::T_IDENTIFIER);
         $parser->match(Lexer::T_OPEN_PARENTHESIS);
diff --git a/src/Query/Sqlite/Week.php b/src/Query/Sqlite/Week.php
index b48299d7..a550a2d3 100644
--- a/src/Query/Sqlite/Week.php
+++ b/src/Query/Sqlite/Week.php
@@ -15,7 +15,7 @@ class Week extends NumberFromStrfTime
      */
     public $mode;
 
-    public function parse(\Doctrine\ORM\Query\Parser $parser)
+    public function parse(\Doctrine\ORM\Query\Parser $parser): void
     {
         $parser->match(Lexer::T_IDENTIFIER);
         $parser->match(Lexer::T_OPEN_PARENTHESIS);
@@ -30,7 +30,7 @@ public function parse(\Doctrine\ORM\Query\Parser $parser)
         $parser->match(Lexer::T_CLOSE_PARENTHESIS);
     }
 
-    protected function getFormat()
+    protected function getFormat(): string
     {
         return '%W';
     }
diff --git a/src/Query/Sqlite/WeekDay.php b/src/Query/Sqlite/WeekDay.php
index 3680cafe..99635afd 100644
--- a/src/Query/Sqlite/WeekDay.php
+++ b/src/Query/Sqlite/WeekDay.php
@@ -7,7 +7,7 @@
  */
 class WeekDay extends NumberFromStrfTime
 {
-    protected function getFormat()
+    protected function getFormat(): string
     {
         return '%w';
     }
diff --git a/src/Query/Sqlite/Year.php b/src/Query/Sqlite/Year.php
index 82f406d2..1cd4ae5c 100644
--- a/src/Query/Sqlite/Year.php
+++ b/src/Query/Sqlite/Year.php
@@ -7,7 +7,7 @@
  */
 class Year extends NumberFromStrfTime
 {
-    protected function getFormat()
+    protected function getFormat(): string
     {
         return '%Y';
     }
diff --git a/src/Types/CarbonDateTimeType.php b/src/Types/CarbonDateTimeType.php
index 9bf3c1e9..7535cf79 100644
--- a/src/Types/CarbonDateTimeType.php
+++ b/src/Types/CarbonDateTimeType.php
@@ -8,7 +8,7 @@
 
 class CarbonDateTimeType extends DateTimeType
 {
-    const CARBONDATETIME = 'carbondatetime';
+    public const CARBONDATETIME = 'carbondatetime';
 
     public function getName()
     {
diff --git a/src/Types/CarbonDateTimeTzType.php b/src/Types/CarbonDateTimeTzType.php
index ceba7b6e..08794863 100644
--- a/src/Types/CarbonDateTimeTzType.php
+++ b/src/Types/CarbonDateTimeTzType.php
@@ -8,7 +8,7 @@
 
 class CarbonDateTimeTzType extends DateTimeTzType
 {
-    const CARBONDATETIMETZ = 'carbondatetimetz';
+    public const CARBONDATETIMETZ = 'carbondatetimetz';
 
     public function getName()
     {
diff --git a/src/Types/CarbonDateType.php b/src/Types/CarbonDateType.php
index e3723ac5..0f7ebf82 100644
--- a/src/Types/CarbonDateType.php
+++ b/src/Types/CarbonDateType.php
@@ -8,7 +8,7 @@
 
 class CarbonDateType extends DateType
 {
-    const CARBONDATE = 'carbondate';
+    public const CARBONDATE = 'carbondate';
 
     public function getName()
     {
diff --git a/src/Types/CarbonImmutableDateTimeType.php b/src/Types/CarbonImmutableDateTimeType.php
index 8d15138d..327c95d8 100644
--- a/src/Types/CarbonImmutableDateTimeType.php
+++ b/src/Types/CarbonImmutableDateTimeType.php
@@ -8,7 +8,7 @@
 
 class CarbonImmutableDateTimeType extends DateTimeType
 {
-    const CARBONDATETIME = 'carbondatetime_immutable';
+    public const CARBONDATETIME = 'carbondatetime_immutable';
 
     public function getName()
     {
diff --git a/src/Types/CarbonImmutableDateTimeTzType.php b/src/Types/CarbonImmutableDateTimeTzType.php
index 3964f4d8..f7fa0bc4 100644
--- a/src/Types/CarbonImmutableDateTimeTzType.php
+++ b/src/Types/CarbonImmutableDateTimeTzType.php
@@ -8,7 +8,7 @@
 
 class CarbonImmutableDateTimeTzType extends DateTimeTzType
 {
-    const CARBONDATETIMETZ = 'carbondatetimetz_immutable';
+    public const CARBONDATETIMETZ = 'carbondatetimetz_immutable';
 
     public function getName()
     {
diff --git a/src/Types/CarbonImmutableDateType.php b/src/Types/CarbonImmutableDateType.php
index ec82d612..efc99e2c 100644
--- a/src/Types/CarbonImmutableDateType.php
+++ b/src/Types/CarbonImmutableDateType.php
@@ -8,7 +8,7 @@
 
 class CarbonImmutableDateType extends DateType
 {
-    const CARBONDATE = 'carbondate_immutable';
+    public const CARBONDATE = 'carbondate_immutable';
 
     public function getName()
     {
diff --git a/src/Types/CarbonImmutableTimeType.php b/src/Types/CarbonImmutableTimeType.php
index 11012184..dd55b131 100644
--- a/src/Types/CarbonImmutableTimeType.php
+++ b/src/Types/CarbonImmutableTimeType.php
@@ -8,7 +8,7 @@
 
 class CarbonImmutableTimeType extends TimeType
 {
-    const CARBONTIME = 'carbontime_immutable';
+    public const CARBONTIME = 'carbontime_immutable';
 
     public function getName()
     {
diff --git a/src/Types/CarbonTimeType.php b/src/Types/CarbonTimeType.php
index 00025651..168c5c1e 100644
--- a/src/Types/CarbonTimeType.php
+++ b/src/Types/CarbonTimeType.php
@@ -8,7 +8,7 @@
 
 class CarbonTimeType extends TimeType
 {
-    const CARBONTIME = 'carbontime';
+    public const CARBONTIME = 'carbontime';
 
     public function getName()
     {
diff --git a/src/Types/PolygonType.php b/src/Types/PolygonType.php
index 558de72b..33ee1e8b 100644
--- a/src/Types/PolygonType.php
+++ b/src/Types/PolygonType.php
@@ -7,7 +7,7 @@
 
 class PolygonType extends Type
 {
-    const FIELD = 'polygon';
+    public const FIELD = 'polygon';
 
     public function getSQLDeclaration(array $fieldDeclaration, AbstractPlatform $platform)
     {
diff --git a/src/Types/ZendDateType.php b/src/Types/ZendDateType.php
index a52b7d99..d770afc1 100755
--- a/src/Types/ZendDateType.php
+++ b/src/Types/ZendDateType.php
@@ -17,7 +17,7 @@
  */
 class ZendDateType extends Type
 {
-    const ZENDDATE = 'zenddate';
+    public const ZENDDATE = 'zenddate';
 
     public function getName()
     {