Created
June 1, 2022 09:28
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A Bitfield implementation intended for use with type class derivation on Scala enums
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package tastyquery.util | |
import compiletime.constValue | |
import compiletime.error | |
import compiletime.summonAll | |
sealed abstract class FlagMirror[A <: reflect.Enum](): | |
outer => | |
opaque type FlagSet = Long | |
def EmptyFlagSet: FlagSet = 0L | |
object exports: | |
type FlagSet = outer.FlagSet | |
export outer.EmptyFlagSet | |
// avoid comparisons between `A` and `FlagSet` | |
given CanEqual[FlagSet, FlagSet] = CanEqual.derived | |
given CanEqual[A, A] = CanEqual.derived | |
// methods on `FlagSet` | |
object FlagSet: | |
extension (flags: FlagSet) | |
def isEmpty: Boolean = flags == EmptyFlagSet | |
def |(flag: A): FlagSet = flags | flag.toFlags | |
def is(flag: A): Boolean = (flags & flag.toFlags) != EmptyFlagSet | |
// methods on `A` | |
extension (flag: A) private def toFlags: FlagSet = 1L << flag.ordinal | |
object FlagMirror: | |
transparent inline def exports[A <: reflect.Enum](using m: FlagMirror[A]): m.exports.type = m.exports | |
inline def derived[A <: reflect.Enum](using m: deriving.Mirror.SumOf[A]): FlagMirror[A] = | |
inline if constValue[Tuple.Size[m.MirroredElemTypes]] <= 63 then | |
summonAll[Tuple.Map[m.MirroredElemTypes, [S] =>> S <:< Singleton]] // assert all singleton | |
new FlagMirror[A]() {} | |
else error("FlagsMirror only supports up to 63 flags") |
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