190 lines
7.5 KiB
Idris
190 lines
7.5 KiB
Idris
module Quox.Whnf.Coercion
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import Quox.Whnf.Interface
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import Quox.Whnf.ComputeElimType
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import Quox.Whnf.TypeCase
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%default total
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private
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coeScoped : {s : Nat} -> DScopeTerm d n -> Dim d -> Dim d -> Loc ->
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ScopeTermN s d n -> ScopeTermN s d n
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coeScoped ty p q loc (S names (N body)) =
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S names $ N $ E $ Coe ty p q body loc
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coeScoped ty p q loc (S names (Y body)) =
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ST names $ E $ Coe (weakDS s ty) p q body loc
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where
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weakDS : (by : Nat) -> DScopeTerm d n -> DScopeTerm d (by + n)
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weakDS by (S names (Y body)) = S names $ Y $ weakT by body
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weakDS by (S names (N body)) = S names $ N $ weakT by body
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parameters {auto _ : CanWhnf Term Interface.isRedexT}
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{auto _ : CanWhnf Elim Interface.isRedexE}
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{d, n : Nat} (defs : Definitions) (ctx : WhnfContext d n)
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||| reduce a function application `App (Coe ty p q val) s loc`
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export covering
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piCoe : (ty : DScopeTerm d n) -> (p, q : Dim d) ->
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(val, s : Term d n) -> Loc ->
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Eff Whnf (Subset (Elim d n) (No . isRedexE defs))
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piCoe sty@(S [< i] ty) p q val s loc = do
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-- (coe [i ⇒ π.(x : A) → B] @p @q t) s ⇝
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-- coe [i ⇒ B[𝒔‹i›/x] @p @q ((t ∷ (π.(x : A) → B)‹p/i›) 𝒔‹p›)
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-- where 𝒔‹j› ≔ coe [i ⇒ A] @q @j s
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--
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-- type-case is used to expose A,B if the type is neutral
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let ctx1 = extendDim i ctx
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Element ty tynf <- whnf defs ctx1 ty.term
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(arg, res) <- tycasePi defs ctx1 ty
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let s0 = CoeT i arg q p s s.loc
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body = E $ App (Ann val (ty // one p) val.loc) (E s0) loc
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s1 = CoeT i (arg // (BV 0 i.loc ::: shift 2)) (weakD 1 q) (BV 0 i.loc)
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(s // shift 1) s.loc
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whnf defs ctx $ CoeT i (sub1 res s1) p q body loc
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||| reduce a pair elimination `CasePair pi (Coe ty p q val) ret body loc`
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export covering
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sigCoe : (qty : Qty) ->
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(ty : DScopeTerm d n) -> (p, q : Dim d) -> (val : Term d n) ->
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(ret : ScopeTerm d n) -> (body : ScopeTermN 2 d n) -> Loc ->
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Eff Whnf (Subset (Elim d n) (No . isRedexE defs))
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sigCoe qty sty@(S [< i] ty) p q val ret body loc = do
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-- caseπ (coe [i ⇒ (x : A) × B] @p @q s) return z ⇒ C of { (a, b) ⇒ e }
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-- ⇝
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-- caseπ s ∷ ((x : A) × B)‹p/i› return z ⇒ C
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-- of { (a, b) ⇒
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-- e[(coe [i ⇒ A] @p @q a)/a,
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-- (coe [i ⇒ B[(coe [j ⇒ A‹j/i›] @p @i a)/x]] @p @q b)/b] }
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--
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-- type-case is used to expose A,B if the type is neutral
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let ctx1 = extendDim i ctx
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Element ty tynf <- whnf defs ctx1 ty.term
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(tfst, tsnd) <- tycaseSig defs ctx1 ty
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let [< x, y] = body.names
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a' = CoeT i (weakT 2 tfst) p q (BVT 1 noLoc) x.loc
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tsnd' = tsnd.term //
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(CoeT i (weakT 2 $ tfst // (B VZ noLoc ::: shift 2))
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(weakD 1 p) (B VZ noLoc) (BVT 1 noLoc) y.loc ::: shift 2)
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b' = CoeT i tsnd' p q (BVT 0 noLoc) y.loc
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whnf defs ctx $ CasePair qty (Ann val (ty // one p) val.loc) ret
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(ST body.names $ body.term // (a' ::: b' ::: shift 2)) loc
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||| reduce a dimension application `DApp (Coe ty p q val) r loc`
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export covering
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eqCoe : (ty : DScopeTerm d n) -> (p, q : Dim d) -> (val : Term d n) ->
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(r : Dim d) -> Loc ->
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Eff Whnf (Subset (Elim d n) (No . isRedexE defs))
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eqCoe sty@(S [< j] ty) p q val r loc = do
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-- (coe [j ⇒ Eq [i ⇒ A] L R] @p @q eq) @r
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-- ⇝
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-- comp [j ⇒ A‹r/i›] @p @q (eq ∷ (Eq [i ⇒ A] L R)‹p/j›)
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-- @r { 0 j ⇒ L; 1 j ⇒ R }
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let ctx1 = extendDim j ctx
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Element ty tynf <- whnf defs ctx1 ty.term
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(a0, a1, a, s, t) <- tycaseEq defs ctx1 ty
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let a' = dsub1 a (weakD 1 r)
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val' = E $ DApp (Ann val (ty // one p) val.loc) r loc
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whnf defs ctx $ CompH j a' p q val' r j s j t loc
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||| reduce a pair elimination `CaseBox pi (Coe ty p q val) ret body`
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export covering
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boxCoe : (qty : Qty) ->
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(ty : DScopeTerm d n) -> (p, q : Dim d) -> (val : Term d n) ->
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(ret : ScopeTerm d n) -> (body : ScopeTerm d n) -> Loc ->
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Eff Whnf (Subset (Elim d n) (No . isRedexE defs))
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boxCoe qty sty@(S [< i] ty) p q val ret body loc = do
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-- caseπ (coe [i ⇒ [ρ. A]] @p @q s) return z ⇒ C of { [a] ⇒ e }
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-- ⇝
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-- caseπ s ∷ [ρ. A]‹p/i› return z ⇒ C
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-- of { [a] ⇒ e[(coe [i ⇒ A] p q a)/a] }
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let ctx1 = extendDim i ctx
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Element ty tynf <- whnf defs ctx1 ty.term
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ta <- tycaseBOX defs ctx1 ty
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let a' = CoeT i (weakT 1 ta) p q (BVT 0 noLoc) body.name.loc
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whnf defs ctx $ CaseBox qty (Ann val (ty // one p) val.loc) ret
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(ST body.names $ body.term // (a' ::: shift 1)) loc
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||| pushes a coercion inside a whnf-ed term
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export covering
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pushCoe : BindName ->
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(ty : Term (S d) n) ->
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(p, q : Dim d) -> (0 npq : Not (p `Eqv` q)) =>
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(s : Term d n) -> (0 pc : So (canPushCoe ty s)) => Loc ->
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Eff Whnf (NonRedex Elim d n defs)
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pushCoe i ty p q s loc =
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case ty of
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-- (coe ★ᵢ @_ @_ s) ⇝ (s ∷ ★ᵢ)
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TYPE l tyLoc =>
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whnf defs ctx $ Ann s (TYPE l tyLoc) loc
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-- η expand it so that whnf for App can deal with it
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--
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-- (coe (𝑖 ⇒ π.(x : A) → B) @p @q s)
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-- ⇝
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-- (λ y ⇒ (coe (𝑖 ⇒ π.(x : A) → B) @p @q s) y) ∷ (π.(x : A) → B)‹q/𝑖›
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Pi {} =>
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let inner = Coe (SY [< i] ty) p q s loc in
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whnf defs ctx $
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Ann (LamY !(mnb "y" loc)
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(E $ App (weakE 1 inner) (BVT 0 loc) loc) loc)
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(ty // one q) loc
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-- no η!!!
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-- push into a pair constructor, otherwise still stuck
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--
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-- s̃‹𝑘› ≔ coe (𝑗 ⇒ A‹𝑗/𝑖›) @p @𝑘 s
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-- -----------------------------------------------
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-- (coe (𝑖 ⇒ (x : A) × B) @p @q (s, t))
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-- ⇝
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-- (s̃‹q›, coe (𝑖 ⇒ B[s̃‹𝑖›/x]) @p @q t)
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-- ∷ ((x : A) × B)‹q/𝑖›
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Sig tfst tsnd tyLoc => do
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let Pair fst snd sLoc = s
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fst' = CoeT i tfst p q fst fst.loc
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fstInSnd =
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CoeT !(fresh i)
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(tfst // (BV 0 loc ::: shift 2))
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(weakD 1 p) (BV 0 loc) (dweakT 1 s) fst.loc
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snd' = CoeT i (sub1 tsnd fstInSnd) p q snd snd.loc
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whnf defs ctx $
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Ann (Pair (E fst') (E snd') sLoc) (ty // one q) loc
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-- (coe {𝐚̄} @_ @_ s) ⇝ (s ∷ {𝐚̄})
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Enum cases tyLoc =>
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whnf defs ctx $ Ann s (Enum cases tyLoc) loc
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-- η expand, same as for Π
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--
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-- (coe (𝑖 ⇒ Eq (𝑗 ⇒ A) l r) @p @q s)
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-- ⇝
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-- (δ 𝑘 ⇒ (coe (𝑖 ⇒ Eq (𝑗 ⇒ A) l r) @p @q s) @𝑘) ∷ (Eq (𝑗 ⇒ A) l r)‹q/𝑖›
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Eq {} =>
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let inner = Coe (SY [< i] ty) p q s loc in
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whnf defs ctx $
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Ann (DLamY !(mnb "k" loc)
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(E $ DApp (dweakE 1 inner) (BV 0 loc) loc) loc)
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(ty // one q) loc
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-- (coe ℕ @_ @_ s) ⇝ (s ∷ ℕ)
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Nat tyLoc =>
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whnf defs ctx $ Ann s (Nat tyLoc) loc
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-- η expand
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--
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-- (coe (𝑖 ⇒ [π. A]) @p @q s)
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-- ⇝
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-- [case1 coe (𝑖 ⇒ [π. A]) @p @q s return A‹q/𝑖› of {[x] ⇒ x}]
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-- ∷ [π. A]‹q/𝑖›
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BOX qty inner tyLoc =>
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let inner = CaseBox {
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qty = One,
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box = Coe (SY [< i] ty) p q s loc,
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ret = SN $ ty // one q,
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body = SY [< !(mnb "x" loc)] $ BVT 0 loc,
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loc
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}
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in
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whnf defs ctx $ Ann (Box (E inner) loc) (ty // one q) loc
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