docs: private static Matcher<ExpressionTree> methodReturnsSameTypeAsReceiver() {
      return new Matcher<ExpressionTree>() {
        @Override
        public boolean matches(ExpressionTree expressionTree, VisitorState state) {
          return isSameType(
              ASTHelpers.getReceiverType(expressionTree),
              ASTHelpers.getReturnType(expressionTree),
              state);
        }
      };
    }