Honestly, issue 10142 contains a kind of enhancement.
From 2.063, all of enum values and enum members are internally wrapped by VarDeclaration to make UDA for them workable (== fixing issue 9652). But currently dmd disables abstract/override/final attribute for enum variable declarations.
class C {
override enum int x1 = 1; // currently NG
abstract enum int x2 = 1; // currently NG
final enum int x3 = 1; // currently NG
But I think this is unnecessary limitation. Relax such limitation would automatically your first enum issue. So
10142 contains both regression fix and enhancement.
Note that the enhancement never break currently accepted code.
Kenji Hara