err

    • Couldn't match type ‘Inner mode [Authorization tok pat]’
                     with ‘Inner mode [Authorization tok pat0]’
      Expected type: PermsF mode -> Inner mode [Authorization tok pat0]
        Actual type: PermsF mode -> Inner mode [Authorization tok pat]
      NB: ‘Inner’ is a non-injective type family
      The type variable ‘pat0’ is ambiguous
    • In the ambiguity check for ‘hasPerm’
      To defer the ambiguity check to use sites, enable AllowAmbiguousTypes
      In the type signature:
        hasPerm :: User -> PermSelector tok pat -> T.Text -> GerdM tok

f.hs

data Mode = Field | Descr

type family Inner tag field where
  Inner Field f = Maybe f
  Inner Descr f = T.Text
  
type PermSelector tok pat = forall mode. PermsF mode -> Inner mode [Authorization tok pat]

hasPerm :: User -> PermSelector tok pat -> T.Text -> GerdM tok
hasPerm = ...

data PermsF f = PermsF
  { permApiVersions       :: Inner f [SimpleAuthorization]
  , permServerList        :: Inner f [Authorization'']
  , permServerView        :: Inner f [Authorization'']
  , permSearch            :: Inner f [Authorization'']
  , permFlushCache        :: Inner f [Authorization'']
  , permStatistics        :: Inner f [Authorization'']
  , permZoneCreate        :: Inner f [Authorization'']
  , permZoneList          :: Inner f [Authorization Filtered DomPat]
  , permZoneView          :: Inner f [Authorization Filtered DomPat]
  , permZoneUpdate        :: Inner f [Authorization' DomPat]
  , permZoneUpdateRecords :: Inner f [Authorization DomTyPat DomPat]
  , permZoneDelete        :: Inner f [Authorization' DomPat]
  , permZoneTriggerAxfr   :: Inner f [Authorization' DomPat]
  , permZoneGetAxfr       :: Inner f [Authorization' DomPat]
  , permZoneNotifySlaves  :: Inner f [Authorization' DomPat]
  , permZoneRectify       :: Inner f [Authorization' DomPat]
  , permZoneMetadata      :: Inner f [Authorization' DomPat]
  , permZoneCryptokeys    :: Inner f [Authorization' DomPat]
  , permTSIGKeyList       :: Inner f [Authorization'']
  , permTSIGKeyCreate     :: Inner f [Authorization'']
  , permTSIGKeyView       :: Inner f [Authorization'']
  , permTSIGKeyUpdate     :: Inner f [Authorization'']
  , permTSIGKeyDelete     :: Inner f [Authorization'']
  }