erasure to untyped syntax

This commit is contained in:
rhiannon morris 2023-09-30 18:37:44 +02:00
parent 8f8b282d07
commit c023845ed7
3 changed files with 453 additions and 2 deletions

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@ -73,7 +73,7 @@ namespace TContext
zeroFor : Context tm n -> QOutput n
zeroFor ctx = Zero <$ ctx
private
public export
extendLen : Telescope a n1 n2 -> Singleton n1 -> Singleton n2
extendLen [<] x = x
extendLen (tel :< _) x = [|S $ extendLen tel x|]

450
lib/Quox/Untyped/Erase.idr Normal file
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@ -0,0 +1,450 @@
module Quox.Untyped.Erase
import Quox.Definition
import Quox.Syntax.Term.Base as Q
import Quox.Syntax.Term.Subst
import Quox.Untyped.Syntax as U
import Quox.Typing.Context
import Quox.Whnf
import Quox.EffExtra
import Data.Singleton
import Data.SnocVect
import Language.Reflection
%default total
%language ElabReflection
%hide TT.Name
public export
data IsErased = Erased | Kept
public export
isErased : Qty -> IsErased
isErased Zero = Erased
isErased One = Kept
isErased Any = Kept
public export
ifErased : Qty -> Lazy a -> Lazy a -> a
ifErased pi x y = case isErased pi of
Erased => x
Kept => y
public export
EContext : Nat -> Type
EContext = Context' IsErased
public export
record ErasureContext d n where
constructor MkEContexts
{auto dimLen : Singleton d}
{auto termLen : Singleton n}
dnames : BContext d
tnames : BContext n
tctx : TContext d n
erased : EContext n
%name ErasureContext ctx
public export
TypeError : Type
TypeError = Typing.Error.Error
%hide Typing.Error.Error
public export
data Error =
CompileTimeOnly (ErasureContext d n) (Q.Term d n)
| ErasedVar (ErasureContext d n) (Var n)
| NotInScope Name
| WrapTypeError TypeError
public export
Erase : List (Type -> Type)
Erase = [Except Error, DefsReader, NameGen]
export
toWhnfContext : ErasureContext d n -> WhnfContext d n
toWhnfContext (MkEContexts {dnames, tnames, tctx, _}) =
MkWhnfContext {dnames, tnames, tctx}
export
(.names) : ErasureContext d n -> NameContexts d n
ctx.names = MkNameContexts ctx.dnames ctx.tnames
export
liftWhnf : Eff Whnf a -> Eff Erase a
liftWhnf act = runEff act
[\x => send x, \case (Err e) => throw $ WrapTypeError e]
export covering
whnf0 : {0 isRedex : RedexTest tm} -> CanWhnf tm isRedex =>
ErasureContext d n -> SQty ->
tm d n -> Eff Erase (tm d n)
whnf0 ctx sg tm = do
let Val n = ctx.termLen; Val d = ctx.dimLen
liftWhnf $ whnf0 !(askAt DEFS) (toWhnfContext ctx) sg tm
export covering
computeElimType : ErasureContext d n -> SQty -> Elim d n -> Eff Erase (Term d n)
computeElimType ctx sg e = do
let Val n = ctx.termLen; Val d = ctx.dimLen
ctx = toWhnfContext ctx
defs <- askAt DEFS
Element e enf <- liftWhnf $ whnf defs ctx sg e
liftWhnf $ computeElimType defs ctx sg e
parameters (ctx : ErasureContext d n) (loc : Loc)
private covering %macro
expect : (forall d, n. Loc -> NameContexts d n -> Term d n -> TypeError) ->
TTImp -> TTImp -> Elab (Term d n -> Eff Erase a)
expect k l r = do
f <- check `(\case ~(l) => Just ~(r); _ => Nothing)
pure $ \t =>
let err = throw $ WrapTypeError $ k loc ctx.names t in
maybe err pure . f =<< whnf0 ctx SZero t
export covering %inline
expectTYPE : Term d n -> Eff Erase Universe
expectTYPE = expect ExpectedTYPE `(TYPE {l, _}) `(l)
export covering %inline
expectPi : Term d n -> Eff Erase (Qty, Term d n, ScopeTerm d n)
expectPi = expect ExpectedPi `(Pi {qty, arg, res, _}) `((qty, arg, res))
export covering %inline
expectSig : Term d n -> Eff Erase (Term d n, ScopeTerm d n)
expectSig = expect ExpectedSig `(Sig {fst, snd, _}) `((fst, snd))
export covering %inline
expectEnum : Term d n -> Eff Erase (SortedSet TagVal)
expectEnum = expect ExpectedEnum `(Enum {cases, _}) `(cases)
export covering %inline
expectEq : Term d n -> Eff Erase (DScopeTerm d n, Term d n, Term d n)
expectEq = expect ExpectedEq `(Eq {ty, l, r, _}) `((ty, l, r))
export covering %inline
expectNat : Term d n -> Eff Erase ()
expectNat = expect ExpectedNat `(Nat {}) `(())
export covering %inline
expectBOX : Term d n -> Eff Erase (Qty, Term d n)
expectBOX = expect ExpectedBOX `(BOX {qty, ty, _}) `((qty, ty))
export
extendTyN : CtxExtension d n1 n2 ->
ErasureContext d n1 -> ErasureContext d n2
extendTyN tel (MkEContexts {termLen, dnames, tnames, tctx, erased}) =
let (qs, xs, ss) = unzip3 tel in
MkEContexts {
dnames,
tnames = tnames . xs,
tctx = tctx . ss,
erased = erased . map isErased qs,
termLen = extendLen tel termLen
}
export
extendTy : Qty -> BindName -> Term d n ->
ErasureContext d n -> ErasureContext d (S n)
extendTy pi x ty = extendTyN [< (pi, x, ty)]
export
extendDim : BindName -> ErasureContext d n -> ErasureContext (S d) n
extendDim i (MkEContexts {dimLen, dnames, tnames, tctx, erased}) =
MkEContexts {
tnames, erased,
dimLen = [|S dimLen|],
dnames = dnames :< i,
tctx = map (dweakT 1) tctx
}
public export
record EraseElimResult d n where
constructor EraRes
type : Lazy (Q.Term d n)
term : U.Term n
export covering
eraseTerm : ErasureContext d n ->
(ty, tm : Q.Term d n) -> Eff Erase (U.Term n)
export covering
eraseElim : ErasureContext d n -> (tm : Q.Elim d n) ->
Eff Erase (EraseElimResult d n)
eraseTerm ctx _ s@(TYPE {}) =
throw $ CompileTimeOnly ctx s
eraseTerm ctx _ s@(Pi {}) =
throw $ CompileTimeOnly ctx s
-- π.x : A ⊢ s ⤋ s' ⇐ B
-- ----------------------------------------
-- (λ x ⇒ s) ⤋ (λ x ⇒ s') ⇐ π.(x : A) → B
--
-- becomes a lambda even when π = 0,
-- to preserve expected evaluation order
eraseTerm ctx ty (Lam body loc) = do
(qty, arg, res) <- expectPi ctx loc ty
let x = body.name
body <- eraseTerm (extendTy qty x arg ctx) res.term body.term
pure $ U.Lam x body loc
eraseTerm ctx _ s@(Sig {}) =
throw $ CompileTimeOnly ctx s
-- s ⤋ s' ⇐ A t ⤋ t' ⇐ B[s/x]
-- ---------------------------------
-- (s, t) ⤋ (s', t') ⇐ (x : A) × B
eraseTerm ctx ty (Pair fst snd loc) = do
(a, b) <- expectSig ctx loc ty
let b = sub1 b (Ann fst a a.loc)
fst <- eraseTerm ctx a fst
snd <- eraseTerm ctx b snd
pure $ Pair fst snd loc
eraseTerm ctx _ s@(Enum {}) =
throw $ CompileTimeOnly ctx s
-- '𝐚 ⤋ '𝐚 ⇐ {⋯}
eraseTerm ctx _ (Tag tag loc) =
pure $ Tag tag loc
eraseTerm ctx ty s@(Eq {}) =
throw $ CompileTimeOnly ctx s
-- 𝑖 ⊢ s ⤋ s' ⇐ A
-- ---------------------------------
-- (δ 𝑖 ⇒ s) ⤋ s' ⇐ Eq (𝑖 ⇒ A) l r
eraseTerm ctx ty (DLam body loc) = do
a <- fst <$> expectEq ctx loc ty
eraseTerm (extendDim body.name ctx) a.term body.term
eraseTerm ctx _ s@(Nat {}) =
throw $ CompileTimeOnly ctx s
-- 0 ⤋ 0 ⇐
eraseTerm _ _ (Zero loc) =
pure $ Zero loc
-- s ⤋ s' ⇐
-- -----------------------
-- succ s ⤋ succ s' ⇐
eraseTerm ctx ty (Succ p loc) = do
p <- eraseTerm ctx ty p
pure $ Succ p loc
eraseTerm ctx ty s@(BOX {}) =
throw $ CompileTimeOnly ctx s
-- [s] ⤋ ⌷ ⇐ [0.A]
--
-- π ≠ 0 s ⤋ s' ⇐ A
-- --------------------
-- [s] ⤋ s' ⇐ [π.A]
eraseTerm ctx ty (Box val loc) = do
(qty, a) <- expectBOX ctx loc ty
case isErased qty of
Erased => pure $ Erased loc
Kept => eraseTerm ctx a val
-- e ⤋ e' ⇒ B
-- ------------
-- e ⤋ e' ⇐ A
eraseTerm ctx ty (E e) =
term <$> eraseElim ctx e
eraseTerm ctx ty (CloT (Sub term th)) =
eraseTerm ctx ty $ pushSubstsWith' id th term
eraseTerm ctx ty (DCloT (Sub term th)) =
eraseTerm ctx ty $ pushSubstsWith' th id term
-- defω x : A = s
-- ----------------
-- x ⤋ x ⇒ A
eraseElim ctx e@(F x u loc) = do
Just def <- asksAt DEFS $ lookup x
| Nothing => throw $ NotInScope x
case isErased def.qty.qty of
Erased => throw $ CompileTimeOnly ctx $ E e
Kept =>
let Val d = ctx.dimLen; Val n = ctx.termLen in
pure $ EraRes def.type $ F x loc
-- π ≠ 0
-- ----------------------------
-- Γ, π.x : A, Γ' ⊢ x ⤋ x ⇒ A
eraseElim ctx e@(B i loc) = do
case ctx.erased !!! i of
Erased => throw $ CompileTimeOnly ctx $ E e
Kept => pure $ EraRes (ctx.tctx !! i) $ B i loc
-- f ⤋ f' ⇒ π.(x : A) → B s ⤋ s' ⇒ A π ≠ 0
-- ---------------------------------------------
-- f s ⤋ f' s' ⇒ B[s/x]
--
-- f ⤋ f' ⇒ 0.(x : A) → B
-- -------------------------
-- f s ⤋ f' ⌷ ⇒ B[s/x]
eraseElim ctx (App fun arg loc) = do
efun <- eraseElim ctx fun
(qty, targ, tres) <- expectPi ctx loc efun.type
let ty = sub1 tres (Ann arg targ arg.loc)
case isErased qty of
Erased => pure $ EraRes ty $ App efun.term (Erased arg.loc) loc
Kept => do arg <- eraseTerm ctx targ arg
pure $ EraRes ty $ App efun.term arg loc
-- e ⤋ e' ⇒ (x : A) × B
-- ρ.x : A, ρ.y : B ⊢ s ⤋ s' ⇐ R[((x,y) ∷ (x : A) × B)/z]
-- x̃ ≔ if ρ = 0 then ⌷ else fst e' ỹ ≔ if ρ = 0 then ⌷ else snd e'
-- -------------------------------------------------------------------
-- (caseρ e return z ⇒ R of {(x, y) ⇒ s}) ⤋ s'[x̃/x, ỹ/y] ⇒ R[e/z]
eraseElim ctx (CasePair qty pair ret body loc) = do
epair <- eraseElim ctx pair
let ty = sub1 (ret // shift 2) $
Ann (Pair (BVT 0 loc) (BVT 1 loc) loc) (weakT 2 epair.type) loc
(tfst, tsnd) <- expectSig ctx loc epair.type
let [< x, y] = body.names
let ctx' = extendTyN [< (qty, x, tfst), (qty, y, tsnd.term)] ctx
body' <- eraseTerm ctx' ty body.term
let x' = ifErased qty (Erased loc) (Fst epair.term loc)
y' = ifErased qty (Erased loc) (Snd epair.term loc)
pure $ EraRes (sub1 ret pair) $ body' // fromSnocVect [< x', y']
-- e ⤋ e' ⇒ (x : A) × B
-- ----------------------
-- fst e ⤋ fst e' ⇒ A
eraseElim ctx (Fst pair loc) = do
epair <- eraseElim ctx pair
a <- fst <$> expectSig ctx loc epair.type
pure $ EraRes a $ Fst epair.term loc
-- e ⤋ e' ⇒ (x : A) × B
-- -----------------------------
-- snd e ⤋ snd e' ⇒ B[fst e/x]
eraseElim ctx (Snd pair loc) = do
epair <- eraseElim ctx pair
b <- snd <$> expectSig ctx loc epair.type
pure $ EraRes (sub1 b (Fst pair loc)) $ Snd epair.term loc
-- case0 e return z ⇒ R of {} ⤋ absurd ⇒ R[e/z]
--
-- s ⤋ s' ⇐ R[𝐚∷{𝐚}/z]
-- -----------------------------------------------
-- case0 e return z ⇒ R of {𝐚 ⇒ s} ⤋ s' ⇒ R[e/z]
--
-- e ⤋ e' ⇒ A ρ ≠ 0 sᵢ ⤋ s'ᵢ ⇐ R[𝐚ᵢ/z]
-- -------------------------------------------------------------------
-- caseρ e return z ⇒ R of {𝐚ᵢ ⇒ sᵢ} ⤋ case e of {𝐚ᵢ ⇒ s'ᵢ} ⇒ R[e/z]
eraseElim ctx e@(CaseEnum qty tag ret arms loc) =
case isErased qty of
Erased => case SortedMap.toList arms of
[] => pure $ EraRes (sub1 ret tag) $ Absurd loc
[(t, arm)] => do
let ty = sub1 ret tag
ty' = sub1 ret (Ann (Tag t loc) (enum [t] loc) loc)
arm' <- eraseTerm ctx ty' arm
pure $ EraRes ty arm'
_ => throw $ CompileTimeOnly ctx $ E e
Kept => do
let ty = sub1 ret tag
etag <- eraseElim ctx tag
arms <- for (SortedMap.toList arms) $ \(t, rhs) => do
let ty' = sub1 ret (Ann (Tag t loc) etag.type loc)
rhs' <- eraseTerm ctx ty' rhs
pure (t, rhs')
pure $ EraRes ty $ CaseEnum etag.term arms loc
-- n ⤋ n' ⇒ z ⤋ z' ⇐ R[zero∷/z]
-- ρ.m : , ς.ih : R[m/z] ⊢ s ⤋ s' ⇐ R[(succ m)∷ℕ/z]
-- ---------------------------------------------------
-- caseρ n return z ⇒ R of {0 ⇒ z; succ m, ς.ih ⇒ s}
-- ⤋
-- case n' of {0 ⇒ z'; succ m, ih ⇒ s'}
-- ⇒ R[n/z]
eraseElim ctx (CaseNat qty qtyIH nat ret zero succ loc) = do
let ty = sub1 ret nat
enat <- eraseElim ctx nat
zero <- eraseTerm ctx (sub1 ret (Ann (Zero loc) (Nat loc) loc)) zero
let [< p, ih] = succ.names
succ <- eraseTerm
(extendTyN [< (qty, p, Nat loc),
(qtyIH, ih, sub1 (ret // shift 1) (BV 0 loc))] ctx)
(sub1 (ret // shift 2) (Ann (Succ (BVT 1 loc) loc) (Nat loc) loc))
succ.term
pure $ EraRes ty $ CaseNat enat.term zero p ih succ loc
-- b ⤋ b' ⇒ [π.A] π ≠ 0
-- πρ.x : A ⊢ s ⤋ s' ⇐ R[[x]∷[π.A]/z]
-- -------------------------------------------------------
-- caseρ b return z ⇒ R of {[x] ⇒ s} ⤋ s'[b'/x] ⇒ R[b/z]
--
-- b ⇒ [0.A] 0.x : A ⊢ s ⤋ s' ⇐ R[[x]∷[0.A]/z]
-- -------------------------------------------------------
-- caseρ b return z ⇒ R of {[x] ⇒ s} ⤋ s'[⌷/x] ⇒ R[b/z]
eraseElim ctx (CaseBox qty box ret body loc) = do
tbox <- computeElimType ctx SOne box -- [fixme] is there any way to avoid this?
(pi, tinner) <- expectBOX ctx loc tbox
let ctx' = extendTy Zero body.name tinner ctx
bty = sub1 (ret // shift 1) $
Ann (Box (BVT 0 loc) loc) (weakT 1 tbox) loc
case isErased pi of
Kept => do
ebox <- eraseElim ctx box
ebody <- eraseTerm ctx' bty body.term
pure $ EraRes (sub1 ret box) $ ebody // one ebox.term
Erased => do
body' <- eraseTerm ctx' bty body.term
pure $ EraRes (sub1 ret box) $ body' // one (Erased loc)
-- f ⤋ f' ⇒ Eq (𝑖 ⇒ A) l r
-- ------------------------------
-- f @r ⤋ f' ⇒ Ar/𝑖
eraseElim ctx (DApp fun arg loc) = do
efun <- eraseElim ctx fun
a <- fst <$> expectEq ctx loc efun.type
pure $ EraRes (dsub1 a arg) efun.term
-- s ⤋ s' ⇐ A
-- ----------------
-- s ∷ A ⤋ s' ⇒ A
eraseElim ctx (Ann tm ty loc) =
EraRes ty <$> eraseTerm ctx ty tm
-- s ⤋ s' ⇐ Ap/𝑖
-- -----------------------------------
-- coe (𝑖 ⇒ A) @p @q s ⤋ s' ⇒ Aq/𝑖
eraseElim ctx (Coe ty p q val loc) = do
val <- eraseTerm ctx (dsub1 ty p) val
pure $ EraRes (dsub1 ty q) val
-- s ⤋ s' ⇐ A
-- --------------------------------
-- comp A @p @q s @r {⋯} ⤋ s' ⇒ A
--
-- [todo] is this ok? they are equal, but even so,
-- maybe t₀ and t₁ have different performance characteristics
eraseElim ctx (Comp ty p q val r zero one loc) =
EraRes ty <$> eraseTerm ctx ty val
eraseElim ctx t@(TypeCase ty ret arms def loc) =
throw $ CompileTimeOnly ctx $ E t
eraseElim ctx (CloE (Sub term th)) =
eraseElim ctx $ pushSubstsWith' id th term
eraseElim ctx (DCloE (Sub term th)) =
eraseElim ctx $ pushSubstsWith' th id term

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@ -57,4 +57,5 @@ modules =
Quox.Parser.FromParser,
Quox.Parser.FromParser.Error,
Quox.Parser,
Quox.Untyped.Syntax
Quox.Untyped.Syntax,
Quox.Untyped.Erase