[Issue 11711] New: Add __traits(getAliasThis)

[d-bugmail at puremagic.com]

https://d.puremagic.com/issues/show_bug.cgi?id=11711

           Summary: Add __traits(getAliasThis)
           Product: D
           Version: D2
          Platform: All
        OS/Version: All
            Status: NEW
          Severity: enhancement
          Priority: P2
         Component: DMD
        AssignedTo: nobody at puremagic.com
        ReportedBy: k.hara.pg at gmail.com


--- Comment #0 from Kenji Hara <k.hara.pg at gmail.com> 2013-12-07 23:15:46 PST ---
Currently, std.traits.XXXTypeOf is implemented in tricky. To fix the
complexity, I'd like to propose a new __trait.

alias Seq(T...) = T;
alias TypeTuple = Seq;

import std.typetuple;

struct S1
{
    string var;
    alias var this;
}
static assert(__traits(getAliasThis, S1) == TypeTuple!("var"));
// __traits(getAliasThis) returns a tuple of alias this member names
static assert(is(typeof(__traits(getMember, S1.init, __traits(getAliasThis,
S1)[0])) == string));
// Extract the alias this type by using the combination with
__traits(getMember).

struct S2
{
    TypeTuple!(int, string) var;
    alias var this;
}
static assert(__traits(getAliasThis, S2) == TypeTuple!("var"));
static assert(is(typeof(__traits(getMember, S2.init, __traits(getAliasThis,
S2)[0])) == TypeTuple!(int, string)));

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