Index normal forms with relevance.

- Remove container types.
- Replace sum types with booleans.
- Remove type annotation from absurd.
- Add original type as argument to cast.
- Make if (was case) take a lambda for the return type.

1 files changed, 194 insertions, 65 deletions

diff --git a/src/Obs/Typing/Conversion.idr b/src/Obs/Typing/Conversion.idr
index 37bdf67..d5dc86a 100644
--- a/src/Obs/Typing/Conversion.idr
+++ b/src/Obs/Typing/Conversion.idr
@@ -1,6 +1,12 @@
 module Obs.Typing.Conversion
 
-import Data.Fin
+import Control.Monad.Maybe
+import Control.Monad.Trans
+
+import Data.Bool
+import Data.So
+
+import Decidable.Equality
 
 import Obs.Logging
 import Obs.NormalForm
@@ -8,71 +14,194 @@ import Obs.NormalForm.Normalise
 import Obs.Sort
 import Obs.Substitution
 
--- Conversion ------------------------------------------------------------------
+%default total
 
--- invariant: all definitions fully expanded
--- invariant: m |- t, u <- a : s
-partial export
-convert : (t, u, a : NormalForm n) -> Sort -> Logging ann Bool
-partial
-convertSet : (t, u : NormalForm n) -> Logging ann Bool
-partial
-convertSum : (t, u : NormalForm n) -> (s, s' : Sort) -> (a, b : NormalForm n) -> Logging ann Bool
+-- Conversion ------------------------------------------------------------------
 
--- In sort Prop
-convert Irrel Irrel a Prop = pure True
--- In unknown type in set
-convert t u (Ntrl _) (Set k) = pure $ t == u
--- In type Set
-convert t u (Cnstr (Sort _)) (Set _) = convertSet t u
--- In type Pi
-convert t u (Cnstr (Pi s s' var a b)) (Set k) = do
-  t <- doApp (weaken 1 t) (Ntrl $ Var var FZ)
-  u <- doApp (weaken 1 u) (Ntrl $ Var var FZ)
-  convert t u b s'
--- In type Sigma
-convert t u (Cnstr (Sigma s s' var a b)) (Set k) = do
-  t1 <- doFst t
-  u1 <- doFst t
-  True <- convert t1 u1 a s
-    | False => pure False
-  b <- subst1 t1 b
-  t2 <- doSnd t
-  u2 <- doSnd t
-  convert t2 u2 b s'
--- In type Sum (manually expanding definition of doCase)
-convert t u (Cnstr (Sum s s' a b)) (Set _) = convertSum t u s s' a b
--- In type Container
-convert t u (Cnstr (Container s a s' s'')) (Set l) = do
-  t <- expandContainer t
-  u <- expandContainer u
-  convert (Cnstr t) (Cnstr u) (Cnstr (expandContainerTy s a s' s'')) (Set l)
--- Default
-convert t u a s =
-  inScope "invalid conversion" $ fatal $
-  fillSep {ann} [prettyPrec App t, prettyPrec App u, prettyPrec App a, prettyPrec App s]
+export
+convert : (s : Sort)
+  -> (a : NormalForm True ctx)
+  -> (t, u : NormalForm (isSet s) ctx)
+  -> MaybeT (Logging ann) (NormalForm (isSet s) ctx)
 
-convertSet (Cnstr (Sort s')) (Cnstr (Sort s'')) = pure $ s' == s''
-convertSet (Cnstr (Pi s s' _ a b)) (Cnstr (Pi l l' _ a' b')) =
-  pure $
-  s == l && s' == l' && !(convertSet a a') && !(convertSet b b')
-convertSet (Cnstr (Sigma s s' _ a b)) (Cnstr (Sigma l l' _ a' b')) =
-  pure $
-  s == l && s' == l' && !(convertSet a a') && !(convertSet b b')
-convertSet (Cnstr (Sum s s' a b)) (Cnstr (Sum l l' a' b')) =
-  pure $
-  s == l && s' == l' && !(convertSet a a') && !(convertSet b b')
-convertSet (Cnstr (Container s a s' s'')) (Cnstr (Container l a' l' l'')) =
-  pure $
-  s == l && s' == l' && s'' == l'' && !(convertSet a a')
-convertSet (Cnstr Top) (Cnstr Top) = pure True
-convertSet (Cnstr Bottom) (Cnstr Bottom) = pure True
-convertSet (Ntrl t) u = pure (Ntrl t == u)
-convertSet t (Ntrl u) = pure (t == Ntrl u)
-convertSet t u = pure $ False
+untypedConvert : (t, u : NormalForm True ctx) -> MaybeT (Logging ann) (NormalForm True ctx)
+-- Diagonals
+untypedConvert (Cnstr (Sort s)) (Cnstr (Sort s')) =
+  if s == s' then pure (Cnstr (Sort s)) else nothing
+untypedConvert (Cnstr (Pi s s' var a b)) (Cnstr (Pi l l' _ a' b')) = do
+  let Yes Refl = decEq s l
+    | No _ => nothing
+  lift $ trace "going back to type-directed conversion"
+  a <- assert_total (convert (suc s) (cast s) a a')
+  b <- assert_total (convert (suc s') (cast s') b b')
+  pure (Cnstr $ Pi s s' var a b)
+untypedConvert (Cnstr (Lambda s var t)) (Cnstr (Lambda s' _ u)) = do
+  let Yes Refl = decEq s s'
+    | No _ => nothing
+  lift $ trace "converting under lambda"
+  t <- untypedConvert t u
+  pure (Cnstr $ Lambda s var t)
+untypedConvert (Cnstr (Sigma s s' var a b)) (Cnstr (Sigma l l' _ a' b')) = do
+  let Yes Refl = decEq s l
+    | No _ => nothing
+  lift $ trace "going back to type-directed conversion"
+  a <- assert_total (convert (suc s) (cast s) a a')
+  b <- assert_total (convert (suc s') (cast s') b b')
+  pure (Cnstr $ Sigma s s' var a b)
+untypedConvert (Cnstr (Pair s@(Set _) s'@(Set _) prf t u)) (Cnstr (Pair l l' prf' t' u')) = do
+  let Yes Refl = decEq (s, s') (l, l')
+    | No _ => nothing
+  lift $ trace "converting pair pointwise"
+  t <- untypedConvert t t'
+  u <- untypedConvert u u'
+  pure (Cnstr $ Pair l l' Oh t u)
+untypedConvert (Cnstr (Pair s@(Set _) Prop prf t u)) (Cnstr (Pair l Prop prf' t' u')) = do
+  let Yes Refl = decEq s l
+    | No _ => nothing
+  lift $ trace "converting pair pointwise"
+  t <- untypedConvert t t'
+  pure (Cnstr $ Pair l Prop Oh t Irrel)
+untypedConvert (Cnstr (Pair Prop s'@(Set _) prf t u)) (Cnstr (Pair Prop l' prf' t' u')) = do
+  let Yes Refl = decEq s' l'
+    | No _ => nothing
+  lift $ trace "converting pair pointwise"
+  u <- untypedConvert u u'
+  pure (Cnstr $ Pair Prop l' Oh Irrel u)
+untypedConvert (Cnstr Bool) (Cnstr Bool) = pure (Cnstr Bool)
+untypedConvert (Cnstr True) (Cnstr True) = pure (Cnstr True)
+untypedConvert (Cnstr False) (Cnstr False) = pure (Cnstr False)
+untypedConvert (Cnstr Top) (Cnstr Top) = pure (Cnstr Top)
+untypedConvert (Cnstr Bottom) (Cnstr Bottom) = pure (Cnstr Bottom)
+untypedConvert t@(Ntrl (Var _ _ _ i)) (Ntrl (Var _ _ _ j)) =
+  if elemToNat i == elemToNat j then pure t else nothing
+untypedConvert lhs@(Ntrl (App b t u)) rhs@(Ntrl (App b' t' u')) = do
+  let Yes Refl = decEq b b'
+    | No _ => nothing
+  lift $ trace "checking parts of a spine"
+  t <- untypedConvert (assert_smaller lhs (Ntrl t)) (assert_smaller rhs (Ntrl t'))
+  let True = b'
+    | False => lift $ doApp t Irrel
+  u <- untypedConvert u u'
+  lift $ doApp t u
+untypedConvert lhs@(Ntrl (Fst b t)) rhs@(Ntrl (Fst b' t')) = do
+  lift $ trace "checking full pair for fst"
+  t <- untypedConvert (assert_smaller lhs (Ntrl t)) (assert_smaller rhs (Ntrl t'))
+  lift $ doFst True b t
+untypedConvert lhs@(Ntrl (Snd b t)) rhs@(Ntrl (Snd b' t')) = do
+  lift $ trace "checking full pair for snd"
+  t <- untypedConvert (assert_smaller lhs (Ntrl t)) (assert_smaller rhs (Ntrl t'))
+  lift $ doSnd b True (rewrite orTrueTrue b in t)
+untypedConvert lhs@(Ntrl (If t f g)) rhs@(Ntrl (If t' f' g')) = do
+  lift $ trace "checking all branches of if"
+  t <- untypedConvert (assert_smaller lhs (Ntrl t)) (assert_smaller rhs (Ntrl t'))
+  f <- untypedConvert f f'
+  g <- untypedConvert g g'
+  lift $ doIf t f g
+untypedConvert (Ntrl Absurd) (Ntrl Absurd) = pure (Ntrl Absurd)
+untypedConvert lhs@(Ntrl (Equal a t u)) rhs@(Ntrl (Equal a' t' u')) = do
+  lift $ trace "checking equal (stuck on type)"
+  a <- untypedConvert (assert_smaller lhs (Ntrl a)) (assert_smaller rhs (Ntrl a'))
+  t <- untypedConvert t t'
+  u <- untypedConvert u u'
+  lift $ doEqual _ a t u
+untypedConvert lhs@(Ntrl (EqualL t u)) rhs@(Ntrl (EqualL t' u')) = do
+  lift $ trace "checking equal (stuck on left)"
+  t <- untypedConvert (assert_smaller lhs (Ntrl t)) (assert_smaller rhs (Ntrl t'))
+  u <- untypedConvert u u'
+  lift $ doEqualSet t u
+untypedConvert lhs@(Ntrl (EqualR t u)) rhs@(Ntrl (EqualR t' u')) = do
+  lift $ trace "checking equal (stuck on right)"
+  t <- untypedConvert (assert_smaller lhs (Cnstr t)) (assert_smaller rhs (Cnstr t'))
+  u <- untypedConvert (assert_smaller lhs (Ntrl u)) (assert_smaller rhs (Ntrl u'))
+  lift $ doEqualSet t u
+untypedConvert lhs@(Ntrl (EqualStuck t u)) rhs@(Ntrl (EqualStuck t' u')) = do
+  lift $ trace "checking equal (head mismatch)"
+  t <- untypedConvert (assert_smaller lhs (Cnstr t)) (assert_smaller rhs (Cnstr t'))
+  u <- untypedConvert (assert_smaller lhs (Cnstr u)) (assert_smaller rhs (Cnstr u'))
+  lift $ doEqualSet t u
+untypedConvert lhs@(Ntrl (CastL a b t)) rhs@(Ntrl (CastL a' b' t')) = do
+  lift $ trace "checking cast (stuck on left)"
+  a <- untypedConvert (assert_smaller lhs (Ntrl a)) (assert_smaller rhs (Ntrl a'))
+  b <- untypedConvert b b'
+  t <- untypedConvert t t'
+  lift $ doCast _ a b t
+untypedConvert lhs@(Ntrl (CastR a b t)) rhs@(Ntrl (CastR a' b' t')) = do
+  lift $ trace "checking cast (stuck on right)"
+  a <- untypedConvert (assert_smaller lhs (Cnstr a)) (assert_smaller rhs (Cnstr a'))
+  b <- untypedConvert (assert_smaller lhs (Ntrl b)) (assert_smaller rhs (Ntrl b'))
+  t <- untypedConvert t t'
+  lift $ doCast _ a b t
+untypedConvert lhs@(Ntrl (CastStuck a b t)) rhs@(Ntrl (CastStuck a' b' t')) = do
+  lift $ trace "checking cast (stuck on left)"
+  a <- untypedConvert (assert_smaller lhs (Cnstr a)) (assert_smaller rhs (Cnstr a'))
+  b <- untypedConvert (assert_smaller lhs (Cnstr b)) (assert_smaller rhs (Cnstr b'))
+  t <- untypedConvert t t'
+  lift $ doCast _ a b t
+-- Pi types
+untypedConvert t@(Cnstr (Lambda s var _)) (Ntrl u) = do
+  u <- lift $ doApp (Ntrl $ weaken [isSet s] u) (point (var, (s ** Refl)) Here)
+  assert_total (untypedConvert t (Cnstr (Lambda s var u)))
+untypedConvert (Ntrl t) u@(Cnstr (Lambda s var _)) = do
+  t <- lift $ doApp (Ntrl $ weaken [isSet s] t) (point (var, (s ** Refl)) Here)
+  assert_total (untypedConvert (Cnstr (Lambda s var t)) u)
+-- Sigma types
+untypedConvert t@(Cnstr (Pair s s' prf _ _)) t'@(Ntrl _) =
+  let t'' : NormalForm (isSet s || isSet s') ctx
+      t'' = rewrite trans (sym $ maxIsSet s s') (soToEq prf) in t'
+  in do
+  t' <- lift $ doFst (isSet s) (isSet s') t''
+  u' <- lift $ doSnd (isSet s) (isSet s') t''
+  assert_total (untypedConvert t (Cnstr (Pair s s' prf t' u')))
+untypedConvert t@(Ntrl _) t'@(Cnstr (Pair s s' prf _ _)) =
+  let t'' : NormalForm (isSet s || isSet s') ctx
+      t'' = rewrite trans (sym $ maxIsSet s s') (soToEq prf) in t
+  in do
+  t <- lift $ doFst (isSet s) (isSet s') t''
+  u <- lift $ doSnd (isSet s) (isSet s') t''
+  assert_total (untypedConvert (Cnstr (Pair s s' prf t u)) t')
+-- Bools
+-- no cases because diagonals complete
+-- Fallback
+untypedConvert _ _ = nothing
 
-convertSum (Cnstr (Left t)) (Cnstr (Left u)) s s' a b = convert t u a s
-convertSum (Cnstr (Right t)) (Cnstr (Right u)) s s' a b = convert t u b s'
-convertSum (Ntrl t) u s s' a b = pure (Ntrl t == u)
-convertSum t (Ntrl u) s s' a b = pure (t == Ntrl u)
-convertSum t u s s' a b = pure False
+convert Prop a Irrel Irrel = pure Irrel
+convert (Set k) (Ntrl a) t u = do
+  lift $ trace $ pretty {ann} "cannot do type-directed conversion on" <++> pretty a
+  untypedConvert t u
+convert (Set k) (Cnstr (Sort s)) t u = do
+  lift $ trace $ pretty {ann} "converting in type" <++> pretty s
+  untypedConvert t u
+convert (Set k) (Cnstr (Pi s s'@(Set _) var a b)) t u = do
+  -- s' must be Set, otherwise ty is in Prop
+  lift $ trace "converting pi type"
+  t' <- lift $ doApp (Sorted.weaken [isSet s] t) (point (var, (s ** Refl)) Here)
+  u' <- lift $ doApp (Sorted.weaken [isSet s] u) (point (var, (s ** Refl)) Here)
+  t <- convert s' b t' u'
+  pure (Cnstr $ Lambda s var t)
+convert (Set k) ty@(Cnstr (Sigma s@(Set j) s' var a b)) t u = do
+  lift $ trace "converting sigma type"
+  t1 <- lift $ doFst True (isSet s') t
+  u1 <- lift $ doFst True (isSet s') u
+  t1 <- convert s a t1 u1
+  t2 <- lift $ doSnd True (isSet s') t
+  u2 <- lift $ doSnd True (isSet s') u
+  b <- lift $ subst1 t1 b
+  t2 <- convert s' (assert_smaller ty b) t2 u2
+  pure (Cnstr $ Pair s s' Oh t1 t2)
+convert (Set k) ty@(Cnstr (Sigma Prop s'@(Set _) var a b)) t u = do
+  lift $ trace "converting sigma type (snd only)"
+  t2 <- lift $ doSnd False True t
+  u2 <- lift $ doSnd False True u
+  b <- lift $ subst1 Irrel b
+  t2 <- convert s' (assert_smaller ty b) t2 u2
+  pure (Cnstr $ Pair Prop s' Oh Irrel t2)
+convert (Set 0) (Cnstr Bool) (Cnstr True) (Cnstr True) = do
+  lift $ trace "converting bool (true)"
+  pure (Cnstr True)
+convert (Set 0) (Cnstr Bool) (Cnstr False) (Cnstr False) = do
+  lift $ trace "converting bool (false)"
+  pure (Cnstr False)
+convert (Set k) (Cnstr Bool) t@(Ntrl _) u@(Ntrl _) = do
+  lift $ trace "converting bool (neutral)"
+  untypedConvert t u
+convert (Set k) (Cnstr a) t u = lift $ inScope "bad type constructor" $ fatal a