better reading with isInvalid as method

EmailValidator/Parser/DoubleQuote.php

@@ -17,7 +17,7 @@ class DoubleQuote extends Parser
     {
 
         $validQuotedString = $this->checkDQUOTE();
-        if(!$validQuotedString->isValid()) return $validQuotedString;
+        if($validQuotedString->isInvalid()) return $validQuotedString;
 
         $special = array(
             EmailLexer::S_CR => true,
@@ -55,7 +55,7 @@ class DoubleQuote extends Parser
 
         if ($prev['type'] === EmailLexer::S_BACKSLASH) {
             $validQuotedString = $this->checkDQUOTE();
-            if(!$validQuotedString->isValid()) return $validQuotedString;
+            if($validQuotedString->isInvalid()) return $validQuotedString;
         }
 
         if (!$this->lexer->isNextToken(EmailLexer::S_AT) && $prev['type'] !== EmailLexer::S_BACKSLASH) {

EmailValidator/Parser/LocalPart.php

@@ -28,7 +28,7 @@ class LocalPart extends Parser
                 $dquoteParsingResult = $this->parseDoubleQuote();
 
                 //Invalid double quote parsing
-                if(!$dquoteParsingResult->isValid()) {
+                if($dquoteParsingResult->isInvalid()) {
                     return $dquoteParsingResult;
                 }
             }
@@ -36,7 +36,7 @@ class LocalPart extends Parser
             if ($this->lexer->token['type'] === EmailLexer::S_OPENPARENTHESIS || 
                 $this->lexer->token['type'] === EmailLexer::S_CLOSEPARENTHESIS ) {
                 $result = $commentParser->parse('remove');
-                if(!$result->isValid()) {
+                if($result->isInvalid()) {
                     return $result;
                 }
                 $warns = $commentParser->getWarnings();
@@ -55,7 +55,7 @@ class LocalPart extends Parser
 
             //$this->warnEscaping();
             $resultEscaping = $this->validateEscaping();
-            if (!$resultEscaping->isValid()) {
+            if ($resultEscaping->isInvalid()) {
                 return $resultEscaping;
             }
 

EmailValidator/Result/InvalidEmail.php

@@ -20,6 +20,11 @@ class InvalidEmail implements Result
         return false;
     }
 
+    public function isInvalid(): bool
+    {
+        return true;
+    }
+
     public function description(): string
     {
         return $this->reason->description() . " in char " . $this->token;

EmailValidator/Result/Result.php

@@ -9,6 +9,12 @@ interface Result
      */
     public function isValid() : bool;
 
+    /**
+     * Is validation result invalid?
+     * Usually the inverse of isValid()
+     */
+    public function isInvalid() : bool;
+
     /**
      * Short description of the result, human readable.
      */

EmailValidator/Result/ValidEmail.php

@@ -9,6 +9,11 @@ class ValidEmail implements Result
         return true;
     }
 
+    public function isInvalid(): bool
+    {
+        return false;
+    }
+
     public function description(): string
     {
         return "Valid email";