Cannot initialize associative array

[rumbu]

According to this 
(https://dlang.org/spec/hash-map.html#static_initialization) this 
is correct static initialization for AA:


immutable RoundingMode[string] ibmRounding =
[
     ">" : RoundingMode.towardPositive,
     "<" : RoundingMode.towardNegative,
     "0" : RoundingMode.towardZero,
     "=0": RoundingMode.tiesToEven,
     "=^": RoundingMode.tiesToAway
];


Error: non-constant expression `[">":cast(RoundingMode)2, 
"<":cast(RoundingMode)3, "0":cast(RoundingMode)4, 
"=0":cast(RoundingMode)0, "=^":cast(RoundingMode)1]`			

RoundingMode is an enum.