type K = enum ka,kb type A = object case kind: K of ka: adata:int of kb: bdata:string proc a():A = A(kind:ka) var an = a() proc `data=`[T:int|string](m:var A,val:T) = when T is int: if m.kind != ka: m.reset m.kind = ka m.adata = val elif T is string: if m.kind != kb: m.reset m.kind = kb m.bdata = val an.data = 5 echo an.kind, an.adata an.data = "hello" echo an.kind, an.bdata