lean4-htt/tests/elab/funind_expr.lean
Garmelon 08eb78a5b2
chore: switch to new test/bench suite (#12590)
This PR sets up the new integrated test/bench suite. It then migrates
all benchmarks and some related tests to the new suite. There's also
some documentation and some linting.

For now, a lot of the old tests are left alone so this PR doesn't become
even larger than it already is. Eventually, all tests should be migrated
to the new suite though so there isn't a confusing mix of two systems.
2026-02-25 13:51:53 +00:00

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import Lean.Elab.Tactic.Guard
inductive Expr where
| nat : Nat → Expr
| plus : Expr → Expr → Expr
| bool : Bool → Expr
| and : Expr → Expr → Expr
inductive Ty where
| nat
| bool
deriving DecidableEq
inductive HasType : Expr → Ty → Prop
| nat : HasType (.nat v) .nat
| plus : HasType a .nat → HasType b .nat → HasType (.plus a b) .nat
| bool : HasType (.bool v) .bool
| and : HasType a .bool → HasType b .bool → HasType (.and a b) .bool
theorem HasType.det (h₁ : HasType e t₁) (h₂ : HasType e t₂) : t₁ = t₂ := by
cases h₁ <;> cases h₂ <;> rfl
inductive Maybe (p : α → Prop) where
| found : (a : α) → p a → Maybe p
| unknown
notation "{{ " x " | " p " }}" => Maybe (fun x => p)
def Expr.typeCheck (e : Expr) : {{ ty | HasType e ty }} :=
match e with
| nat .. => .found .nat .nat
| bool .. => .found .bool .bool
| plus a b =>
match a.typeCheck, b.typeCheck with
| .found .nat h₁, .found .nat h₂ => .found .nat (.plus h₁ h₂)
| _, _ => .unknown
| and a b =>
match a.typeCheck, b.typeCheck with
| .found .bool h₁, .found .bool h₂ => .found .bool (.and h₁ h₂)
| _, _ => .unknown
termination_by e
theorem Expr.typeCheck_correct (h₁ : HasType e ty) (h₂ : e.typeCheck ≠ .unknown)
: e.typeCheck = .found ty h := by
revert h₂
cases typeCheck e with
| found ty' h' => intro; have := HasType.det h₁ h'; subst this; rfl
| unknown => intros; contradiction
/--
info: Expr.typeCheck.induct (motive : Expr → Prop) (case1 : ∀ (a : Nat), motive (Expr.nat a))
(case2 : ∀ (a : Bool), motive (Expr.bool a))
(case3 :
∀ (a b : Expr) (h₁ : HasType a Ty.nat) (h₂ : HasType b Ty.nat),
b.typeCheck = Maybe.found Ty.nat h₂ →
a.typeCheck = Maybe.found Ty.nat h₁ → motive a → motive b → motive (a.plus b))
(case4 :
∀ (a b : Expr),
(∀ (h₁ : HasType a Ty.nat) (h₂ : HasType b Ty.nat),
a.typeCheck = Maybe.found Ty.nat h₁ → b.typeCheck = Maybe.found Ty.nat h₂ → False) →
motive a → motive b → motive (a.plus b))
(case5 :
∀ (a b : Expr) (h₁ : HasType a Ty.bool) (h₂ : HasType b Ty.bool),
b.typeCheck = Maybe.found Ty.bool h₂ →
a.typeCheck = Maybe.found Ty.bool h₁ → motive a → motive b → motive (a.and b))
(case6 :
∀ (a b : Expr),
(∀ (h₁ : HasType a Ty.bool) (h₂ : HasType b Ty.bool),
a.typeCheck = Maybe.found Ty.bool h₁ → b.typeCheck = Maybe.found Ty.bool h₂ → False) →
motive a → motive b → motive (a.and b))
(e : Expr) : motive e
-/
#guard_msgs in
#check Expr.typeCheck.induct
/-
This no longer works after splitting non-refining tail-call matches,
as we now have different number of variables
theorem Expr.typeCheck_complete {e : Expr} : e.typeCheck = .unknown → ¬ HasType e ty := by
apply Expr.typeCheck.induct (motive := fun e => e.typeCheck = .unknown → ¬ HasType e ty)
<;> simp [typeCheck]
<;> {
intro _ _ a b iha ihb
split <;> simp [*]
intro ht; cases ht
next hnp h₁ h₂ => exact hnp h₁ h₂ (typeCheck_correct h₁ (iha · h₁)) (typeCheck_correct h₂ (ihb · h₂))
}
-/
-- The same, using the induction tactic
theorem Expr.typeCheck_complete' {e : Expr} : e.typeCheck = .unknown → ¬ HasType e ty := by
induction e using typeCheck.induct
all_goals simp [typeCheck]
case case3 | case5 => simp [*]
case case4 iha ihb | case6 iha ihb =>
intro ht; cases ht
next hnp h₁ h₂ => exact hnp h₁ h₂ (typeCheck_correct h₁ (iha · h₁)) (typeCheck_correct h₂ (ihb · h₂))