public ISemantReturn<ImmutableList<Tuple<Option<String>, ExprType>>> GetMembers(Env env, ImmutableList<StructDecln> memberDeclns) {
var result = memberDeclns.Aggregate(ImmutableList<Tuple<Option<String>, ExprType>>.Empty, (acc, decln) => acc.AddRange(Semant(decln.GetMemberDeclns, ref env))
);
return SemantReturn.Create(env, result);
}