102 lines
3.8 KiB
Agda
102 lines
3.8 KiB
Agda
module Lib.Erasure
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import Lib.Types
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import Data.Maybe
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import Data.SnocList
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import Lib.TopContext
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EEnv : U
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EEnv = List (String × Quant × Maybe Tm)
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-- TODO look into removing Nothing below, can we recover all of the types?
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-- Idris does this in `chk` for linearity checking.
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-- check App at type
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getType : Tm -> M (Maybe Tm)
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getType (Ref fc nm x) = do
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top <- get
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case lookup nm top of
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Nothing => error fc "\{show nm} not in scope"
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(Just (MkEntry _ name type def)) => pure $ Just type
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getType tm = pure Nothing
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erase : EEnv -> Tm -> List (FC × Tm) -> M Tm
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-- App a spine using type
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eraseSpine : EEnv -> Tm -> List (FC × Tm) -> (ty : Maybe Tm) -> M Tm
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eraseSpine env tm Nil _ = pure tm
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eraseSpine env t ((fc, arg) :: args) (Just (Pi fc1 str icit Zero a b)) = do
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let u = Erased (getFC arg)
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eraseSpine env (App fc t u) args (Just b)
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eraseSpine env t ((fc, arg) :: args) (Just (Pi fc1 str icit Many a b)) = do
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u <- erase env arg Nil
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-- TODO this seems wrong, we need to subst u into b to get the type
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eraseSpine env (App fc t u) args (Just b)
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-- eraseSpine env t ((fc, arg) :: args) (Just ty) = do
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-- error fc "ceci n'est pas une ∏ \{showTm ty}" -- e.g. Bnd 1
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eraseSpine env t ((fc, arg) :: args) _ = do
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u <- erase env arg Nil
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eraseSpine env (App fc t u) args Nothing
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doAlt : EEnv -> CaseAlt -> M CaseAlt
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-- REVIEW do we extend env?
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doAlt env (CaseDefault t) = CaseDefault <$> erase env t Nil
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doAlt env (CaseCons name args t) = do
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top <- get
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let (Just (MkEntry _ str type def)) = lookup name top
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| _ => error emptyFC "\{show name} dcon missing from context"
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let env' = piEnv env type args
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CaseCons name args <$> erase env' t Nil
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where
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piEnv : EEnv -> Tm -> List String -> EEnv
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piEnv env (Pi fc nm icit rig t u) (arg :: args) = piEnv ((arg, rig, Just t) :: env) u args
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piEnv env _ _ = env
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doAlt env (CaseLit lit t) = CaseLit lit <$> erase env t Nil
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-- Check erasure and insert "Erased" value
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-- We have a solution for Erased values, so important thing here is checking.
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-- build stack, see what to do when we hit a non-app
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-- This is a little fuzzy because we don't have all of the types.
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erase env t sp = case t of
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(App fc u v) => erase env u ((fc,v) :: sp)
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(Ref fc nm x) => do
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top <- get
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case lookup nm top of
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Nothing => error fc "\{show nm} not in scope"
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(Just (MkEntry _ name type def)) => eraseSpine env t sp (Just type)
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(Lam fc nm icit rig u) => Lam fc nm icit rig <$> erase ((nm, rig, Nothing) :: env) u Nil
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-- If we get here, we're looking at a runtime pi type
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(Pi fc nm icit rig u v) => do
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u' <- erase env u Nil
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v' <- erase ((nm, Many, Just u) :: env) v Nil
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eraseSpine env (Pi fc nm icit rig u' v') sp (Just $ UU emptyFC)
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-- leaving as-is for now, we don't know the quantity of the apps
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(Meta fc k) => pure t
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(Case fc u alts) => do
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-- REVIEW check if this pushes to env, and write that down or get an index on there
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u' <- erase env u Nil
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alts' <- traverse (doAlt env) alts
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eraseSpine env (Case fc u' alts') sp Nothing
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(Let fc nm u v) => do
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u' <- erase env u Nil
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v' <- erase ((nm, Many, Nothing) :: env) v Nil
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eraseSpine env (Let fc nm u' v') sp Nothing
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(LetRec fc nm ty u v) => do
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u' <- erase ((nm, Many, Just ty) :: env) u Nil
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v' <- erase ((nm, Many, Just ty) :: env) v Nil
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eraseSpine env (LetRec fc nm ty u' v') sp Nothing
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(Bnd fc k) => do
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case getAt (cast k) env of
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Nothing => error fc "bad index \{show k}"
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-- This is working, but empty FC
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Just (nm, Zero, ty) => error fc "used erased value \{show nm} (FIXME FC may be wrong here)"
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Just (nm, Many, ty) => eraseSpine env t sp ty
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(UU fc) => eraseSpine env t sp (Just $ UU fc)
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(Lit fc lit) => eraseSpine env t sp Nothing
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Erased fc => error fc "erased value in relevant context" -- eraseSpine env t sp Nothing
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