Issue with traits usability

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On Wednesday, 21 March 2018 at 15:36:01 UTC, Márcio Martins wrote:
> Hi!
>
> How do I get past this?
>
>
> static struct X {
> 	int x;
> 	private enum T = 1;
> 	private alias M = string;
> }
>
> foreach (Member; __traits(allMembers, X)) {
> 	pragma(msg, __traits(getProtection, __traits(getMember, X, 
> Member)));
> }
>
>
> Output:
>
> public
> private
> c.d(1084): Error: argument string has no protection
> c.d(1084):        while evaluating pragma(msg, 
> __traits(getProtection, string))
>
>
> What I want to achieve essentially is skip all X's aliases and 
> templates, but get everything else, like enums and data 
> members. How would I go about this in a robust way?
> I actually want to skip aliases, and templates.

In addition to Simen's answer, you can you 
std.traits.FieldNameTuple to get only the fields of your struct 
(which only includes struct members that are actually part of the 
struct's memory layout):

import std.traits;

static struct X {
	int x;
	private enum T = 1;
	private alias M = string;
}

void main()
{
     foreach (Member; FieldNameTuple!X) {
         pragma(msg, __traits(getProtection, __traits(getMember, 
X, Member)));
     }
}

This example prints "public" once.