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124 lines
4 KiB
Agda
124 lines
4 KiB
Agda
module Luau.Type where
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open import FFI.Data.Maybe using (Maybe; just; nothing; just-inv)
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open import Agda.Builtin.Equality using (_≡_; refl)
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open import Properties.Dec using (Dec; yes; no)
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open import Properties.Equality using (cong)
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data Type : Set where
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nil : Type
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_⇒_ : Type → Type → Type
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bot : Type
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top : Type
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_∪_ : Type → Type → Type
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_∩_ : Type → Type → Type
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lhs : Type → Type
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lhs (T ⇒ _) = T
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lhs (T ∪ _) = T
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lhs (T ∩ _) = T
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lhs nil = nil
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lhs bot = bot
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lhs top = top
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rhs : Type → Type
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rhs (_ ⇒ T) = T
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rhs (_ ∪ T) = T
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rhs (_ ∩ T) = T
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rhs nil = nil
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rhs bot = bot
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rhs top = top
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_≡ᵀ_ : ∀ (T U : Type) → Dec(T ≡ U)
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nil ≡ᵀ nil = yes refl
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nil ≡ᵀ (S ⇒ T) = no (λ ())
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nil ≡ᵀ bot = no (λ ())
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nil ≡ᵀ top = no (λ ())
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nil ≡ᵀ (S ∪ T) = no (λ ())
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nil ≡ᵀ (S ∩ T) = no (λ ())
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(S ⇒ T) ≡ᵀ nil = no (λ ())
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(S ⇒ T) ≡ᵀ (U ⇒ V) with (S ≡ᵀ U) | (T ≡ᵀ V)
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(S ⇒ T) ≡ᵀ (S ⇒ T) | yes refl | yes refl = yes refl
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(S ⇒ T) ≡ᵀ (U ⇒ V) | _ | no p = no (λ q → p (cong rhs q))
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(S ⇒ T) ≡ᵀ (U ⇒ V) | no p | _ = no (λ q → p (cong lhs q))
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(S ⇒ T) ≡ᵀ bot = no (λ ())
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(S ⇒ T) ≡ᵀ top = no (λ ())
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(S ⇒ T) ≡ᵀ (U ∪ V) = no (λ ())
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(S ⇒ T) ≡ᵀ (U ∩ V) = no (λ ())
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bot ≡ᵀ nil = no (λ ())
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bot ≡ᵀ (U ⇒ V) = no (λ ())
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bot ≡ᵀ bot = yes refl
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bot ≡ᵀ top = no (λ ())
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bot ≡ᵀ (U ∪ V) = no (λ ())
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bot ≡ᵀ (U ∩ V) = no (λ ())
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top ≡ᵀ nil = no (λ ())
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top ≡ᵀ (U ⇒ V) = no (λ ())
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top ≡ᵀ bot = no (λ ())
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top ≡ᵀ top = yes refl
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top ≡ᵀ (U ∪ V) = no (λ ())
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top ≡ᵀ (U ∩ V) = no (λ ())
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(S ∪ T) ≡ᵀ nil = no (λ ())
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(S ∪ T) ≡ᵀ (U ⇒ V) = no (λ ())
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(S ∪ T) ≡ᵀ bot = no (λ ())
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(S ∪ T) ≡ᵀ top = no (λ ())
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(S ∪ T) ≡ᵀ (U ∪ V) with (S ≡ᵀ U) | (T ≡ᵀ V)
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(S ∪ T) ≡ᵀ (S ∪ T) | yes refl | yes refl = yes refl
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(S ∪ T) ≡ᵀ (U ∪ V) | _ | no p = no (λ q → p (cong rhs q))
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(S ∪ T) ≡ᵀ (U ∪ V) | no p | _ = no (λ q → p (cong lhs q))
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(S ∪ T) ≡ᵀ (U ∩ V) = no (λ ())
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(S ∩ T) ≡ᵀ nil = no (λ ())
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(S ∩ T) ≡ᵀ (U ⇒ V) = no (λ ())
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(S ∩ T) ≡ᵀ bot = no (λ ())
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(S ∩ T) ≡ᵀ top = no (λ ())
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(S ∩ T) ≡ᵀ (U ∪ V) = no (λ ())
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(S ∩ T) ≡ᵀ (U ∩ V) with (S ≡ᵀ U) | (T ≡ᵀ V)
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(S ∩ T) ≡ᵀ (U ∩ V) | yes refl | yes refl = yes refl
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(S ∩ T) ≡ᵀ (U ∩ V) | _ | no p = no (λ q → p (cong rhs q))
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(S ∩ T) ≡ᵀ (U ∩ V) | no p | _ = no (λ q → p (cong lhs q))
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_≡ᴹᵀ_ : ∀ (T U : Maybe Type) → Dec(T ≡ U)
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nothing ≡ᴹᵀ nothing = yes refl
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nothing ≡ᴹᵀ just U = no (λ ())
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just T ≡ᴹᵀ nothing = no (λ ())
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just T ≡ᴹᵀ just U with T ≡ᵀ U
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(just T ≡ᴹᵀ just T) | yes refl = yes refl
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(just T ≡ᴹᵀ just U) | no p = no (λ q → p (just-inv q))
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data Mode : Set where
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strict : Mode
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nonstrict : Mode
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src : Mode → Type → Type
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src m nil = bot
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src m (S ⇒ T) = S
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-- In nonstrict mode, functions are covaraiant, in strict mode they're contravariant
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src strict (S ∪ T) = (src strict S) ∩ (src strict T)
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src nonstrict (S ∪ T) = (src nonstrict S) ∪ (src nonstrict T)
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src strict (S ∩ T) = (src strict S) ∪ (src strict T)
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src nonstrict (S ∩ T) = (src nonstrict S) ∩ (src nonstrict T)
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src strict bot = top
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src nonstrict bot = bot
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src strict top = bot
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src nonstrict top = top
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tgt : Type → Type
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tgt nil = bot
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tgt (S ⇒ T) = T
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tgt bot = bot
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tgt top = top
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tgt (S ∪ T) = (tgt S) ∪ (tgt T)
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tgt (S ∩ T) = (tgt S) ∩ (tgt T)
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optional : Type → Type
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optional nil = nil
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optional (T ∪ nil) = (T ∪ nil)
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optional T = (T ∪ nil)
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normalizeOptional : Type → Type
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normalizeOptional (S ∪ T) with normalizeOptional S | normalizeOptional T
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normalizeOptional (S ∪ T) | (S′ ∪ nil) | (T′ ∪ nil) = (S′ ∪ T′) ∪ nil
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normalizeOptional (S ∪ T) | S′ | nil = optional S′
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normalizeOptional (S ∪ T) | nil | T′ = optional T′
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normalizeOptional (S ∪ T) | S′ | T′ = S′ ∪ T′
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normalizeOptional T = T
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