code: private Node parseAndRecordParamTypeNode(JsDocToken token) {
      checkArgument(token == JsDocToken.LEFT_CURLY);
      int lineno = stream.getLineno();
      int startCharno = stream.getCharno();
  
      Node typeNode = parseParamTypeExpressionAnnotation(token);
      recordTypeNode(lineno, startCharno, typeNode, true);
      return typeNode;
    }
docs: Looks for a type expression at the current token and if found,
  returns it. Note that this method consumes input.
  
  Parameter type expressions are special for two reasons:
  <ol>
  <li>They must begin with '{', to distinguish type names from param names.
  <li>They may end in '=', to denote optionality.
  </ol>
  
  @param token The current token.
  @return The type expression found or null if none.