code: private function parseScalarTypeDefinition()
      {
          $start       = $this->lexer->token;
          $description = $this->parseDescription();
          $this->expectKeyword('scalar');
          $name       = $this->parseName();
          $directives = $this->parseDirectives(true);
  
          return new ScalarTypeDefinitionNode([
              'name'        => $name,
              'directives'  => $directives,
              'loc'         => $this->loc($start),
              'description' => $description,
          ]);
      }
docs: @return ScalarTypeDefinitionNode
  
  @throws SyntaxError