Allow illegal code in enum initialization?

[simendsjo]

Illegal code is accepted in static if, but not in enum 
declarations. This leads to having three lines when one is 
enough. Is this just an oversight, or by design?

template T(alias A) {
    enum T = true;
}
void main() {
    struct S { }
    static if(__traits(compiles, S.a) && T!(S.a)) // ok
        enum e1 = true;
    else
        enum e1 = false;
    enum e2 = __traits(compiles, S.a) && T!(S.a); // No property 
S.a
}