5840 – Cannot assign to an array member of struct in CTFE

(This is a bug regarding the trunk version of DMD (commit ea65289). The following code works fine in 2.052.)
In the latest version of DMD on github, assigning to an array member of a struct in compile-time is rejected.
-----------------
struct Foo {
 string g;
}
Foo f() {
 Foo x;
 x.g = "y"; // Error: x.g = "y" cannot be evaluated at compile time
 return x;
}
pragma(msg, f());
-----------------
This causes tuple of string cannot be created in compile-time. The struct literal `Foo("y")` works though.

The bug was introduced in commit d96bbcb3cbf7cd561c47.
(https://github.com/D-Programming-Language/dmd/commit/d96bbcb3cbf7cd561c477497c872d616ae5343a1)

D2 fix: https://github.com/D-Programming-Language/dmd/commit/0c9c52c7123e7336ce732e72099dbebd183742e2 

D1 fix: https://github.com/D-Programming-Language/dmd/commit/bd196a9020883d94c7b7c4d8a91943d5735f4f3c