traits getProtection

[Adam D. Ruppe]

I've prepared a dmd pull request to add a new __trait:
getProtection.

It is meant to be used along with getMember() to add to
the reflection capabilities, letting us use the existing
protection qualifiers as strings.

 From the test:
==
class Test {
     public int a;
     private int b;
     export string c;
     protected int d;
     package void e() {}
}

void main() {
     Test t;
     static assert(__traits(getProtection, __traits(getMember, t, 
"a")) == "public");
     static assert(__traits(getProtection, __traits(getMember, t, 
"b")) == "private");
     static assert(__traits(getProtection, __traits(getMember, t, 
"c")) == "export");
     static assert(__traits(getProtection, __traits(getMember, t, 
"d")) == "protected");
     static assert(__traits(getProtection, __traits(getMember, t, 
"e")) == "package");
}
==



This will help D automatically generate things like
external interfaces that use the protections.

For instance, I plan to use it in my web.d to only
make functions marked "export" available via the
web interface. Currently, you have to use a naming
convention to hide functions - a leading underscore -
even on private members. This is ok, but not great.

But with the protection trait, we can mark it with
a much more natural "private", or any of the other
specifiers D has.


I'm sure other uses will come up too.