segfault in ldc release only - looks like some kind of optimization bug?

[aliak]

Hi,

so I had this weird bug that was driving me crazy and only 
segfaulted with ldc in release build - (I'm using ldc 1.16.0).

This is the code that segfaults. All parts seem to be necessary 
for it to happen, or at least I think so. I've gone in circles 
minimizing so I've probably missed something. But this seems to 
be it:

import std;

struct W(T) {
     T value;
     ref inout(T) front() inout { return value; }
}

auto ref get(T)(W!T value) {
     return value.front;
}

struct S {
     string a;
}

void main() {
     S[string] aa;
     aa = ["one" : S("a")];
     auto b = W!S(aa["one"]).get;
     writeln(b);
}

Running with ldc and -O3 crashes: "ldc2 -O3 -run source.d"

Some things I've noticed:
- if you remove the call to .get and use .value directly, the 
crash goes
- if you remove the inout specifier on front(), the crash goes
- if you remove the ref specifier on front(), the crash goes
- if you don't call writeln(b), the crash goes
- if you don't use the s returned by the aa, the crash goes
- if you *add* a return qualifier on the "front" function, the 
crash goes away

(what is that return thing btw and when do you use it?)

Any ideas?