function parseField(lexer) {
  var start = lexer.token;

  var nameOrAlias = parseName(lexer);
  var alias = void 0;
  var name = void 0;
  if (skip(lexer, _lexer.TokenKind.COLON)) {
    alias = nameOrAlias;
    name = parseName(lexer);
  } else {
    alias = null;
    name = nameOrAlias;
  }

  return {
    kind: _kinds.FIELD,
    alias: alias,
    name: name,
    arguments: parseArguments(lexer),
    directives: parseDirectives(lexer),
    selectionSet: peek(lexer, _lexer.TokenKind.BRACE_L) ? parseSelectionSet(lexer) : null,
    loc: loc(lexer, start)
  };
}
Field : Alias? Name Arguments? Directives? SelectionSet?

Alias : Name :