refactor(ast): use TsProperty constants wherever possible

Author: Brainshaker95

src/Model/Ast/ConstExpr/ConstExprFalseNode.php

@@ -5,6 +5,7 @@
 namespace Brainshaker95\PhpToTsBundle\Model\Ast\ConstExpr;
 
 use Brainshaker95\PhpToTsBundle\Interface\Node;
+use Brainshaker95\PhpToTsBundle\Model\TsProperty;
 use Brainshaker95\PhpToTsBundle\Tool\Assert;
 use PHPStan\PhpDocParser\Ast\ConstExpr\ConstExprFalseNode as PHPStanConstExprFalseNode;
 use PHPStan\PhpDocParser\Ast\Node as PHPStanNode;
@@ -21,7 +22,7 @@ public function __toString(): string
 
     public function toString(): string
     {
-        return 'false';
+        return TsProperty::TYPE_FALSE;
     }
 
     public static function fromPhpStan(PHPStanNode $node): self

src/Model/Ast/ConstExpr/ConstExprNullNode.php

@@ -5,6 +5,7 @@
 namespace Brainshaker95\PhpToTsBundle\Model\Ast\ConstExpr;
 
 use Brainshaker95\PhpToTsBundle\Interface\Node;
+use Brainshaker95\PhpToTsBundle\Model\TsProperty;
 use Brainshaker95\PhpToTsBundle\Tool\Assert;
 use PHPStan\PhpDocParser\Ast\ConstExpr\ConstExprNullNode as PHPStanConstExprNullNode;
 use PHPStan\PhpDocParser\Ast\Node as PHPStanNode;
@@ -21,7 +22,7 @@ public function __toString(): string
 
     public function toString(): string
     {
-        return 'null';
+        return TsProperty::TYPE_NULL;
     }
 
     public static function fromPhpStan(PHPStanNode $node): self

src/Model/Ast/ConstExpr/ConstExprTrueNode.php

@@ -5,6 +5,7 @@
 namespace Brainshaker95\PhpToTsBundle\Model\Ast\ConstExpr;
 
 use Brainshaker95\PhpToTsBundle\Interface\Node;
+use Brainshaker95\PhpToTsBundle\Model\TsProperty;
 use Brainshaker95\PhpToTsBundle\Tool\Assert;
 use PHPStan\PhpDocParser\Ast\ConstExpr\ConstExprTrueNode as PHPStanConstExprTrueNode;
 use PHPStan\PhpDocParser\Ast\Node as PHPStanNode;
@@ -21,7 +22,7 @@ public function __toString(): string
 
     public function toString(): string
     {
-        return 'true';
+        return TsProperty::TYPE_TRUE;
     }
 
     public static function fromPhpStan(PHPStanNode $node): self

src/Model/Ast/Type/NullableTypeNode.php

@@ -5,6 +5,7 @@
 namespace Brainshaker95\PhpToTsBundle\Model\Ast\Type;
 
 use Brainshaker95\PhpToTsBundle\Interface\Node;
+use Brainshaker95\PhpToTsBundle\Model\TsProperty;
 use Brainshaker95\PhpToTsBundle\Tool\Assert;
 use Brainshaker95\PhpToTsBundle\Tool\PhpStan;
 use PHPStan\PhpDocParser\Ast\Node as PHPStanNode;
@@ -26,7 +27,7 @@ public function __toString(): string
 
     public function toString(): string
     {
-        return '(' . $this->type . ' | null)';
+        return '(' . $this->type . ' | ' . TsProperty::TYPE_NULL . ')';
     }
 
     public static function fromPhpStan(PHPStanNode $node): self