mirror of
https://github.com/idris-lang/Idris2.git
synced 2024-12-21 10:41:59 +03:00
225 lines
7.4 KiB
Idris
225 lines
7.4 KiB
Idris
module Deriving.Common
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import Data.SnocList
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import Language.Reflection
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%default total
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------------------------------------------------------------------------------
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-- Being free of a variable
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||| IsFreeOf is parametrised by
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||| @ x the name of the type variable that the functioral action will change
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||| @ ty the type that does not contain any mention of x
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export
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data IsFreeOf : (x : Name) -> (ty : TTImp) -> Type where
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||| For now we do not bother keeping precise track of the proof that a type
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||| is free of x
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TrustMeFO : IsFreeOf a x
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||| We may need to manufacture proofs and so we provide the `assert` escape hatch.
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export %unsafe
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assert_IsFreeOf : IsFreeOf x ty
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assert_IsFreeOf = TrustMeFO
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||| Testing function deciding whether the given term is free of a particular
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||| variable.
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export
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isFreeOf : (x : Name) -> (ty : TTImp) -> Maybe (IsFreeOf x ty)
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isFreeOf x ty
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= do isOk <- flip mapMTTImp ty $ \case
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t@(IVar _ v) => t <$ guard (v /= x)
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t => pure t
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pure TrustMeFO
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------------------------------------------------------------------------------
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-- Being a (data) type
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public export
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record IsType where
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constructor MkIsType
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typeConstructor : Name
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parameterNames : List (Argument Name, Nat)
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dataConstructors : List (Name, TTImp)
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wording : NameType -> String
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wording Bound = "a bound variable"
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wording Func = "a function name"
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wording (DataCon tag arity) = "a data constructor"
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wording (TyCon tag arity) = "a type constructor"
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isTypeCon : Elaboration m => FC -> Name -> m (List (Name, TTImp))
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isTypeCon fc ty = do
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[(_, MkNameInfo (TyCon _ _))] <- getInfo ty
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| [] => failAt fc "\{show ty} out of scope"
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| [(_, MkNameInfo nt)] => failAt fc "\{show ty} is \{wording nt} rather than a type constructor"
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| _ => failAt fc "\{show ty} is ambiguous"
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cs <- getCons ty
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for cs $ \ n => do
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[(_, ty)] <- getType n
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| _ => failAt fc "\{show n} is ambiguous"
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pure (n, ty)
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export
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isType : Elaboration m => TTImp -> m IsType
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isType = go Z [] where
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go : Nat -> List (Argument Name, Nat) -> TTImp -> m IsType
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go idx acc (IVar fc n) = MkIsType n (map (map (minus idx . S)) acc) <$> isTypeCon fc n
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go idx acc (IApp _ t (IVar _ nm)) = case nm of
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-- Unqualified: that's a local variable
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UN (Basic _) => go (S idx) ((Arg emptyFC nm, idx) :: acc) t
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_ => go (S idx) acc t
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go idx acc (INamedApp _ t nm (IVar _ nm')) = case nm' of
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-- Unqualified: that's a local variable
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UN (Basic _) => go (S idx) ((NamedArg emptyFC nm nm', idx) :: acc) t
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_ => go (S idx) acc t
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go idx acc (IAutoApp _ t (IVar _ nm)) = case nm of
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-- Unqualified: that's a local variable
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UN (Basic _) => go (S idx) ((AutoArg emptyFC nm, idx) :: acc) t
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_ => go (S idx) acc t
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go idx acc t = failAt (getFC t) "Expected a type constructor, got: \{show t}"
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------------------------------------------------------------------------------
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-- Being a (data) constructor with a parameter
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-- TODO: generalise?
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public export
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record ConstructorView where
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constructor MkConstructorView
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params : SnocList (Name, Nat)
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conArgTypes : List (Count, Argument TTImp)
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export
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constructorView : TTImp -> Maybe ConstructorView
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constructorView (IPi fc rig pinfo x a b) = do
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let Just arg = fromPiInfo fc pinfo x a
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| Nothing => constructorView b -- this better be a boring argument...
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let True = rig /= M1
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| False => constructorView b -- this better be another boring argument...
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{ conArgTypes $= ((rig, arg) ::) } <$> constructorView b
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constructorView f = do
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MkAppView _ ts _ <- appView f
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let range = [<] <>< [0..minus (length ts) 1]
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let ps = flip mapMaybe (zip ts range) $ \ t => the (Maybe (Name, Nat)) $ case t of
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(Arg _ (IVar _ nm), n) => Just (nm, n)
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_ => Nothing
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pure (MkConstructorView ps [])
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------------------------------------------------------------------------------
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-- Satisfying an interface
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--
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-- In order to derive Functor for `data Tree a = Node (List (Tree a))`, we need
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-- to make sure that `Functor List` already exists. This is done using the following
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-- convenience functions.
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export
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withParams : FC -> (Nat -> Maybe TTImp) -> List (Argument Name, Nat) -> TTImp -> TTImp
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withParams fc params nms t = go nms where
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addConstraint : Maybe TTImp -> Name -> TTImp -> TTImp
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addConstraint Nothing _ = id
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addConstraint (Just cst) nm =
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let ty = IApp fc cst (IVar fc nm) in
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IPi fc MW AutoImplicit Nothing ty
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go : List (Argument Name, Nat) -> TTImp
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go [] = t
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go ((arg, pos) :: nms)
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= let nm = unArg arg in
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IPi fc M0 ImplicitArg (Just nm) (Implicit fc True)
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$ addConstraint (params pos) nm
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$ go nms
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||| Type of proofs that something has a given type
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export
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data HasType : (nm : Name) -> (ty : TTImp) -> Type where
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TrustMeHT : HasType nm ty
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export
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hasType : Elaboration m => (nm : Name) ->
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m (Maybe (ty : TTImp ** HasType nm ty))
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hasType nm = catch $ do
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[(_, ty)] <- getType nm
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| _ => fail "Ambiguous name"
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pure (ty ** TrustMeHT)
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||| Type of proofs that a type is inhabited
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export
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data IsProvable : (ty : TTImp) -> Type where
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TrustMeIP : IsProvable ty
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export
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isProvable : Elaboration m => (ty : TTImp) ->
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m (Maybe (IsProvable ty))
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isProvable ty = catch $ do
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ty <- check {expected = Type} ty
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ignore $ check {expected = ty} `(%search)
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pure TrustMeIP
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||| Type of proofs that a type satisfies a constraint.
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||| Internally it's vacuous. We don't export the constructor so
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||| that users cannot manufacture buggy proofs.
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export
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data HasImplementation : (intf : a -> Type) -> TTImp -> Type where
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TrustMeHI : HasImplementation intf t
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||| We may need to manufacture proofs and so we provide the `assert` escape hatch.
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export %unsafe
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assert_hasImplementation : HasImplementation intf t
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assert_hasImplementation = TrustMeHI
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||| Given
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||| @ intf an interface (e.g. `Functor`, or `Bifunctor`)
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||| @ t a term corresponding to a (possibly partially applied) type constructor
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||| check whether Idris2 can find a proof that t satisfies the interface.
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export
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hasImplementation : Elaboration m => (intf : a -> Type) -> (t : TTImp) ->
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m (Maybe (HasImplementation intf t))
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hasImplementation c t = catch $ do
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prf <- isType t
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intf <- quote c
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ty <- check {expected = Type} $ withParams emptyFC (const Nothing) prf.parameterNames `(~(intf) ~(t))
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ignore $ check {expected = ty} `(%search)
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pure TrustMeHI
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------------------------------------------------------------------------------
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-- Utils
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||| Optionally eta-expand if there is no argument available
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export
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optionallyEta : FC -> Maybe TTImp -> (TTImp -> TTImp) -> TTImp
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optionallyEta fc (Just t) f = f t
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optionallyEta fc Nothing f =
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let tnm = UN $ Basic "t" in
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ILam fc MW ExplicitArg (Just tnm) (Implicit fc False) $
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f (IVar fc tnm)
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||| We often apply multiple arguments, this makes things simpler
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export
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apply : FC -> TTImp -> List TTImp -> TTImp
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apply fc t ts = apply t (map (Arg fc) ts)
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||| Use unqualified names (useful for more compact printing)
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export
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cleanup : TTImp -> TTImp
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cleanup = \case
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IVar fc n => IVar fc (dropNS n)
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t => t
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||| Create fresh names
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export
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freshName : List Name -> String -> String
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freshName ns a = assert_total $ go (basicNames ns) Nothing where
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basicNames : List Name -> List String
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basicNames = mapMaybe $ \ nm => case dropNS nm of
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UN (Basic str) => Just str
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_ => Nothing
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covering
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go : List String -> Maybe Nat -> String
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go ns mi =
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let nm = a ++ maybe "" show mi in
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ifThenElse (nm `elem` ns) (go ns (Just $ maybe 0 S mi)) nm
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