-- Capless/Typing/Basic.lean

import Capless.Typing

import Capless.Subcapturing

import Capless.Subcapturing.Basic

import Capless.Subtyping.Basic

namespace Capless

-- Repository definitions used:
content: notation:max "{x=" x "}" => CaptureSet.singleton x

content: notation:max "{c=" c "}" => CaptureSet.csingleton c

content: notation:50 "λ[X<:" S "]" t => Term.tlam S t

content: notation:40 "let" "x=" t " in " u => Term.letin t u

content: notation:40 "let" "(c,x)=" t " in " u => Term.letex t u

content: notation:40 "let" "X=" S " in " t => Term.bindt S t

content: notation:40 "let" "c=" C " in " t => Term.bindc C t

content: notation:50 "λ(x:" T ")" t => Term.lam T t

content: notation:50 "λ[c<:" B "]" t => Term.clam B t

content: notation:40 "Label[" S "]" => SType.label S

content: notation:30 Γ ",c:=" C => Context.cvar Γ (CBinding.inst C)

content: notation:50 "∀(x:" T ")" U => SType.forall T U

content: notation:50 "∀[c<:" B "]" T => SType.cforall B T

content: notation:30 Γ ",c<:" B => Context.cvar Γ (CBinding.bound B)

content: notation:30 Γ ",X<:" T => Context.tvar Γ (TBinding.bound T)

content: notation:30 Γ ",X:=" T => Context.tvar Γ (TBinding.inst T)

content: notation:50 Γ " ⊢ " E1 " <:e " E2 => ESubtyp Γ E1 E2

content: notation:50 Γ " ⊢ " T1 " <:s " T2 => SSubtyp Γ T1 T2

content: notation:50 Γ " ⊢ " T1 " <: " T2 => CSubtyp Γ T1 T2

content: notation:40 Γ " ⊢ " t:80 " : " E " @ " C => Typed Γ t E C

content: notation:50 Γ " ⊢ " C1 " <:c " C2 => Subcapt Γ C1 C2

content: notation:30 Γ ",x:" T => Context.var Γ T

content: notation:30 Γ ",c<:*" => Context.cvar Γ (CBinding.bound CBound.star)

content: notation:50 "∀[X<:" S "]" T => SType.tforall S T

content: notation:40 "∃c." T => EType.ex T

content: notation:40 "boundary:" S " in " t => Term.boundary S t

content: inductive EType : Nat -> Nat -> Nat -> Type where
| ex : CType n m (k+1) -> EType n m k
| type : CType n m k -> EType n m k

content: inductive CaptureSet : Nat -> Nat -> Type where
| empty : CaptureSet n k
| union : CaptureSet n k -> CaptureSet n k -> CaptureSet n k
| singleton : Fin n -> CaptureSet n k
| csingleton : Fin k -> CaptureSet n k

content: inductive Typed : Context n m k -> Term n m k -> EType n m k -> CaptureSet n k -> Prop where
| var :
  Context.Bound Γ x (S^C) ->
  Typed Γ (Term.var x) (S^{x=x}) {x=x}
| label :
  Context.LBound Γ x S ->
  Typed Γ (Term.var x) (Label[S]^{x=x}) {x=x}
| pack :
  Typed (Γ.cvar (CBinding.inst C)) (Term.var x) (EType.type T) {x=x} ->
  Typed Γ (Term.pack C x) (∃c.T) {}
| sub :
  Typed Γ t E1 C1 ->
  (Γ ⊢ C1 <:c C2) ->
  (Γ ⊢ E1 <:e E2) ->
  Typed Γ t E2 C2
| abs {C : CaptureSet n k} :
  Typed (Γ,x:T) t E (C.weaken ∪ {x=0}) ->
  Typed Γ (λ(x:T)t) ((∀(x:T)E)^C) {}
| tabs {C : CaptureSet n k} :
  Typed (Γ,X<:S) t E C ->
  Typed Γ (λ[X<:S]t) ((∀[X<:S]E)^C) {}
| cabs {C : CaptureSet n k} :
  Typed (Γ,c<:B) t E C.cweaken ->
  Typed Γ (λ[c<:B]t) ((∀[c<:B]E)^C) {}
| app :
  Typed Γ (Term.var x) (EType.type (∀(x:T)E)^C) {x=x} ->
  Typed Γ (Term.var y) T {x=y} ->
  Typed Γ (Term.app x y) (E.open y) ({x=x} ∪ {x=y})
| invoke :
  Typed Γ (Term.var x) (EType.type (Label[S])^C) {x=x} ->
  Typed Γ (Term.var y) (S^{}) {x=y} ->
  Typed Γ (Term.invoke x y) E ({x=x} ∪ {x=y})
| tapp :
  Typed Γ (Term.var x) (EType.type (∀[X<:SType.tvar X]E)^C) {x=x} ->
  Typed Γ (Term.tapp x X) (E.topen X) {x=x}
| capp :
  Typed Γ (Term.var x) (EType.type (∀[c<:CBound.upper {c=c}]E)^C) {x=x} ->
  Typed Γ (Term.capp x c) (E.copen c) {x=x}
| letin :
  Typed Γ t (EType.type T) C ->
  Typed (Γ,x: T) u E.weaken C.weaken ->  
  Typed Γ (let x=t in u) E C
| letex :
  Typed Γ t (EType.ex T) C ->
  Typed ((Γ,c<:*),x: T) u E.cweaken.weaken C.cweaken.weaken ->
  Typed Γ (let (c,x)=t in u) E C
| bindt :
  Typed (Γ,X:=S) t E.tweaken C ->
  Typed Γ (let X=S in t) E C
| bindc :
  Typed (Γ,c:=C) t E.cweaken C0.cweaken ->
  Typed Γ (let c=C in t) E C0
| boundary {Γ : Context n m k} {S : SType n m k} :
  Typed
    ((Γ,c<:CBound.star),x: Label[S.cweaken]^{c=0})
    t
    (S.cweaken.weaken^{}) (C.cweaken.weaken ∪ {c=0} ∪ {x=0}) ->
  Typed Γ (boundary: S in t) (S^CaptureSet.empty) C

content: inductive Subcapt : Context n m k -> CaptureSet n k -> CaptureSet n k -> Prop where
| trans :
  Subcapt Γ C1 C2 ->
  Subcapt Γ C2 C3 ->
  Subcapt Γ C1 C3
| subset :
  C1 ⊆ C2 ->
  Subcapt Γ C1 C2
| union :
  Subcapt Γ C1 C3 ->
  Subcapt Γ C2 C3 ->
  Subcapt Γ (C1 ∪ C2) C3
| var :
  Context.Bound Γ x (CType.capt C S) ->
  Subcapt Γ {x=x} C
| cinstl :
  Context.CBound Γ c (CBinding.inst C) ->
  Subcapt Γ C {c=c}
| cinstr :
  Context.CBound Γ c (CBinding.inst C) ->
  Subcapt Γ {c=c} C
| cbound :
  Context.CBound Γ c (CBinding.bound (CBound.upper C)) ->
  Subcapt Γ {c=c} C

content: inductive Context.Bound : Context n m k -> Fin n -> CType n m k -> Prop where
| here : Bound (var Γ0 E) 0 E.weaken
| there_var :
  Bound Γ x E ->
  Bound (var Γ E') (Fin.succ x) E.weaken
| there_tvar :
  Bound Γ x E ->
  Bound (tvar Γ b) x E.tweaken
| there_cvar :
  Bound Γ x E ->
  Bound (cvar Γ b) x E.cweaken
| there_label :
  Bound Γ x E ->
  Bound (label Γ S) (Fin.succ x) E.weaken

content: inductive Context : Nat -> Nat -> Nat -> Type where
| empty : Context 0 0 0
| var : Context n m k -> CType n m k -> Context (n+1) m k
| label : Context n m k -> SType n m k -> Context (n+1) m k
| tvar : Context n m k -> TBinding n m k -> Context n (m+1) k
| cvar : Context n m k -> CBinding n k -> Context n m (k+1)

content: inductive Context.LBound : Context n m k -> Fin n -> SType n m k -> Prop where
| here : LBound (label Γ0 S) 0 S.weaken
| there_var :
  LBound Γ x S ->
  LBound (var Γ E) x.succ S.weaken
| there_tvar :
  LBound Γ x S ->
  LBound (tvar Γ b) x S.tweaken
| there_cvar :
  LBound Γ x S ->
  LBound (cvar Γ b) x S.cweaken
| there_label :
  LBound Γ x S ->
  LBound (label Γ S') x.succ S.weaken

content: inductive CType : Nat -> Nat -> Nat -> Type where
| capt : CaptureSet n k -> SType n m k -> CType n m k

content: inductive SType : Nat -> Nat -> Nat -> Type where
| top : SType n m k
| tvar : Fin m -> SType n m k
| forall : CType n m k -> EType (n+1) m k -> SType n m k
| tforall : SType n m k -> EType n (m+1) k -> SType n m k
| cforall : CBound n k -> EType n m (k+1) -> SType n m k
| box : CType n m k -> SType n m k
| label : SType n m k -> SType n m k

content: inductive CBound : Nat -> Nat -> Type where
| upper : CaptureSet n k -> CBound n k
| star : CBound n k

content: inductive CaptureSet.Subset : CaptureSet n k → CaptureSet n k → Prop where
| empty : Subset {} C
| rfl : Subset C C
| union_l :
  Subset C1 C ->
  Subset C2 C ->
  Subset (C1 ∪ C2) C
| union_rl :
  Subset C C1 ->
  Subset C (C1 ∪ C2)
| union_rr :
  Subset C C2 ->
  Subset C (C1 ∪ C2)

content: inductive CBinding : Nat -> Nat -> Type where
| bound : CBound n k -> CBinding n k
| inst : CaptureSet n k -> CBinding n k

content: inductive Context.CBound : Context n m k -> Fin k -> CBinding n k -> Prop where
| here : CBound (cvar Γ0 b) 0 b.cweaken
| there_var :
  CBound Γ x b ->
  CBound (var Γ E) x b.weaken
| there_tvar :
  CBound Γ x b ->
  CBound (tvar Γ b') x b
| there_cvar :
  CBound Γ x b ->
  CBound (cvar Γ b') (Fin.succ x) b.cweaken
| there_label :
  CBound Γ x b ->
  CBound (label Γ S) x b.weaken

content: inductive TBinding : Nat -> Nat -> Nat -> Type where
| bound : SType n m k -> TBinding n m k
| inst : SType n m k -> TBinding n m k

content: inductive Term : Nat -> Nat -> Nat -> Type where
 
| var : Fin n -> Term n m k
 
| lam : CType n m k -> Term (n+1) m k -> Term n m k
 
| tlam : SType n m k -> Term n (m+1) k -> Term n m k
 
| clam : CBound n k -> Term n m (k+1) -> Term n m k
 
| pack : CaptureSet n k -> Fin n -> Term n m k
 
| app : Fin n -> Fin n -> Term n m k
 
| invoke : Fin n -> Fin n -> Term n m k
 
| tapp : Fin n -> Fin m -> Term n m k
 
| capp : Fin n -> Fin k -> Term n m k
 
| letin : Term n m k -> Term (n+1) m k -> Term n m k
 
| letex : Term n m k -> Term (n+1) m (k+1) -> Term n m k
 
| bindt : SType n m k -> Term n (m+1) k -> Term n m k
 
| bindc : CaptureSet n k -> Term n m (k+1) -> Term n m k
 
| boundary : SType n m k -> Term (n+1) m (k+1) -> Term n m k

content: @[aesop safe constructors]
inductive Term.IsValue : Term n m k -> Prop where
| lam : Term.IsValue (lam E t)
| tlam : Term.IsValue (tlam S t)
| clam : Term.IsValue (clam B t)
| pack : Term.IsValue (pack c x)

content: inductive ESubtyp : Context n m k -> EType n m k -> EType n m k -> Prop where
| exist :
  CSubtyp (Context.cvar Γ (CBinding.bound CBound.star)) T1 T2 ->
  ESubtyp Γ (EType.ex T1) (EType.ex T2)
| type :
  CSubtyp Γ T1 T2 ->
  ESubtyp Γ (EType.type T1) (EType.type T2)

content: notation:50 "λ(x:" T ")" t => Term.lam T t

content: notation:50 "λ[X<:" S "]" t => Term.tlam S t

content: notation:50 "λ[c<:" B "]" t => Term.clam B t

content: notation:40 "boundary:" S " in " t => Term.boundary S t

content: notation:max "{x=" x "}" => CaptureSet.singleton x

content: notation:max "{c=" c "}" => CaptureSet.csingleton c

content: notation:50 Γ " ⊢ " E1 " <:e " E2 => ESubtyp Γ E1 E2

content: notation:40 Γ " ⊢ " t:80 " : " E " @ " C => Typed Γ t E C

content: notation:50 "∀(x:" T ")" U => SType.forall T U

content: notation:50 "∀[X<:" S "]" T => SType.tforall S T

content: notation:50 "∀[c<:" B "]" T => SType.cforall B T

content: notation:max S " ^ " C => CType.capt C S

content: notation:40 "∃c." T => EType.ex T

content: notation:40 "Label[" S "]" => SType.label S

content: notation:50 Γ " ⊢ " C1 " <:c " C2 => Subcapt Γ C1 C2

-- Repository lemmas used:
content: theorem ESubtyp.type_inv_subcapt
  (h : ESubtyp Γ E (EType.type (CType.capt C S))) :
  ∃ C0 S0, E = EType.type (CType.capt C0 S0) ∧ Subcapt Γ C0 C

content: theorem ESubtyp.type_inv_subcapt'
  (heq : E1 = EType.type (CType.capt C S))
  (h : ESubtyp Γ E E1) :
  ∃ C0 S0, E = EType.type (CType.capt C0 S0) ∧ Subcapt Γ C0 C

content: theorem Subcapt.refl :
  Subcapt Γ C C

-- Local definitions used:

-- Local lemmas used:

-- Target theorem and proof:
theorem Typing.inv_subcapt'
  (he1 : t0 = Term.var x) (he2 : E0 = EType.type (CType.capt C S))
  (h : Typed Γ t0 E0 C0) :
  Subcapt Γ {x=x} C
:= by
  induction h <;> try (solve | cases he1 | cases he2)
  case var =>
    cases he1; cases he2
    apply Subcapt.refl
  case label =>
    cases he1; cases he2
    apply Subcapt.refl
  case sub hsub ih =>
    subst he1 he2
    have h := ESubtyp.type_inv_subcapt hsub
    let ⟨C0, S0, he, hs⟩ := h
    subst he
    have ih := ih rfl rfl
    apply Subcapt.trans; trivial; trivial