Not sure, but I belive this could be one of reasons:
https://issues.dlang.org/show_bug.cgi?id=15989

On Wed, Oct 11, 2017 at 4:54 PM, bauss via Digitalmars-d <digitalmars-d@puremagic.com> wrote:
On Sunday, 8 October 2017 at 04:40:59 UTC, Daniel Kozak wrote:
Up to      2.062  : Failure with output:
-----
onlineapp.d(10): Error: cannot evaluate new Foo("0") at compile time
onlineapp.d(10): Error: cannot evaluate new Foo("1") at compile time
-----

2.063   to 2.072.2: Success with output: Hello D
Since      2.073.2: Failure with output: onlineapp.d(10): Error: variable
onlineapp.aa : Unable to initialize enum with class or pointer to struct.
Use static const variable instead.

https://run.dlang.io/is/mJqayC

On Sun, Oct 8, 2017 at 4:29 AM, bauss via Digitalmars-d < digitalmars-d@puremagic.com> wrote:

[...]

Do you know what the reason for the change is and are there any workarounds to actually declare AA's with classes that can be used at compile-time then?