static init of associative array of enums not working.. why?

[Øivind via Digitalmars-d-learn]

Shouldn't this work? According to "Static Initialization of AAs" 
on this page, it should: https://dlang.org/spec/hash-map.html

enum DevicePropDataType {
  dString,
  dDateTime
}

enum DevicePropValType {
  property,
  miscDate
}

immutable DevicePropDataType[DevicePropValType] propDType =
  [
   DevicePropValType.property:          
DevicePropDataType.dString,
   DevicePropValType.miscDate:          
DevicePropDataType.dDateTime
   ];

void main() {
        
}

I get the following error:
/d847/f751.d(12): Error: non-constant expression 
[cast(DevicePropValType)0:cast(DevicePropDataType)0, 
cast(DevicePropValType)1:cast(DevicePropDataType)1]