add support for nullable type

Author: JanTvrdik

doc/grammer.ebnf

@@ -1,12 +1,16 @@
 Type
   ::= Atomic (Union | Intersection)?
+    | Nullable
 
 Union
   ::= ('|' Atomic)+
 
 Intersection
   ::= ('&' Atomic)+
 
+Nullable
+  ::= '?' Identifier Generic?
+
 Atomic
   ::= Identifier (Generic | Array)?
     | '(' Type ')' Array?

doc/grammer.peg

@@ -1,12 +1,16 @@
 Type
   = Atomic (Union / Intersection)?
+  / Nullable
 
 Union
   = ('|' Atomic)+
 
 Intersection
   = ('&' Atomic)+
 
+Nullable
+  = '?' Identifier Generic?
+
 Atomic
   = Identifier (Generic / Array)?
   / '(' Type ')' Array?

src/Ast/NullableType.php

@@ -0,0 +1,22 @@
+<?php declare(strict_types = 1);
+
+namespace PhpStan\TypeParser\Ast;
+
+
+class NullableType implements Node
+{
+	/** @var Node */
+	public $type;
+
+
+	public function __construct(Node $type)
+	{
+		$this->type = $type;
+	}
+
+
+	public function __toString(): string
+	{
+		return '?' . $this->type;
+	}
+}

src/Lexer.php

@@ -10,7 +10,7 @@ class Lexer
 	const TOKEN_IDENTIFIER = 0;
 	const TOKEN_UNION = 1;
 	const TOKEN_INTERSECTION = 2;
-	const TOKEN_COMPLEMENT = 3;
+	const TOKEN_NULLABLE = 3;
 	const TOKEN_OPEN_PARENTHESES = 4;
 	const TOKEN_CLOSE_PARENTHESES = 5;
 	const TOKEN_OPEN_ANGLE_BRACKET = 6;
@@ -64,7 +64,7 @@ private function initialize(): void
 			self::TOKEN_IDENTIFIER => '(?:[\\\\]?+[a-z_\\x7F-\\xFF][0-9a-z_\\x7F-\\xFF]*+)++',
 			self::TOKEN_UNION => '\\|',
 			self::TOKEN_INTERSECTION => '&',
-			self::TOKEN_COMPLEMENT => '\\~',
+			self::TOKEN_NULLABLE => '\\?',
 			self::TOKEN_OPEN_PARENTHESES => '\\(',
 			self::TOKEN_CLOSE_PARENTHESES => '\\)',
 			self::TOKEN_OPEN_ANGLE_BRACKET => '<',

src/Parser.php

@@ -67,13 +67,18 @@ private function tearDown(): void
 
 	private function parseType(): Ast\Node
 	{
-		$type = $this->parseAtomic();
+		if ($this->tokenType === Lexer::TOKEN_NULLABLE) {
+			$type = $this->parseNullable();
 
-		if ($this->tokenType === Lexer::TOKEN_UNION) {
-			$type = $this->parseUnion($type);
+		} else {
+			$type = $this->parseAtomic();
+
+			if ($this->tokenType === Lexer::TOKEN_UNION) {
+				$type = $this->parseUnion($type);
 
-		} elseif ($this->tokenType === Lexer::TOKEN_INTERSECTION) {
-			$type = $this->parseIntersection($type);
+			} elseif ($this->tokenType === Lexer::TOKEN_INTERSECTION) {
+				$type = $this->parseIntersection($type);
+			}
 		}
 
 		return $type;
@@ -135,6 +140,21 @@ private function parseIntersection(Ast\Node $type): Ast\Node
 	}
 
 
+	private function parseNullable(): Ast\Node
+	{
+		$this->consume(Lexer::TOKEN_NULLABLE);
+
+		$type = new Ast\SimpleNode($this->value());
+		$this->consume(Lexer::TOKEN_IDENTIFIER);
+
+		if ($this->tokenType === Lexer::TOKEN_OPEN_ANGLE_BRACKET) {
+			$type = $this->parseGeneric($type);
+		}
+
+		return new Ast\NullableNode($type);
+	}
+
+
 	private function parseGeneric(Ast\SimpleNode $baseType): Ast\Node
 	{
 		$this->consume(Lexer::TOKEN_OPEN_ANGLE_BRACKET);