lean4-htt/tests/lean/run/funind_proof.lean
Kyle Miller f771dea78b
fix: make sure app elaborator eta feature does not result in capturable variables (#10377)
This PR fixes an issue where the "eta feature" in the app elaborator,
which is invoked when positional arguments are skipped due to named
arguments, results in variables that can be captured by those named
arguments. Now the temporary local variables that implement this feature
get fresh names. The names used for the closed lambda expression still
use the original parameter names.

Closes #6373
2025-09-14 20:19:50 +00:00

71 lines
3 KiB
Text

inductive Term where
| const : String → Term
| app : String → List Term → Term
namespace Term
mutual
def numConsts : Term → Nat
| const _ => 1
| app _ cs => numConstsLst cs
def numConstsLst : List Term → Nat
| [] => 0
| c :: cs => numConsts c + numConstsLst cs
end
mutual
-- Since #4733 this function can be compiled using structural recursion,
-- but then the construction of the functional induction principle falls over
-- TODO: Fix funind, and then omit the `termination_by` here (or test both variants)
def replaceConst (a b : String) : Term → Term
| const c => if a == c then const b else const c
| app f cs => app f (replaceConstLst a b cs)
termination_by t => sizeOf t
def replaceConstLst (a b : String) : List Term → List Term
| [] => []
| c :: cs => replaceConst a b c :: replaceConstLst a b cs
termination_by ts => sizeOf ts
end
/--
info: Term.replaceConst.induct (a : String) (motive1 : Term → Prop) (motive2 : List Term → Prop)
(case1 : ∀ (a_1 : String), (a == a_1) = true → motive1 (const a_1))
(case2 : ∀ (a_1 : String), ¬(a == a_1) = true → motive1 (const a_1))
(case3 : ∀ (a : String) (cs : List Term), motive2 cs → motive1 (app a cs)) (case4 : motive2 [])
(case5 : ∀ (c : Term) (cs : List Term), motive1 c → motive2 cs → motive2 (c :: cs)) (a✝ : Term) : motive1 a✝
-/
#guard_msgs in
#check replaceConst.induct
theorem numConsts_replaceConst (a b : String) (e : Term) : numConsts (replaceConst a b e) = numConsts e := by
apply replaceConst.induct (a := a)
(motive1 := fun e => numConsts (replaceConst a b e) = numConsts e)
(motive2 := fun es => numConstsLst (replaceConstLst a b es) = numConstsLst es)
case case1 => intro c h; guard_hyp h :ₛ (a == c) = true; simp [replaceConst, numConsts, *]
case case2 => intro c h; guard_hyp h :ₛ ¬(a == c) = true; simp [replaceConst, numConsts, *]
case case3 =>
intro f cs ih
guard_hyp ih :ₛnumConstsLst (replaceConstLst a b cs) = numConstsLst cs
simp [replaceConst, numConsts, *]
case case4 => simp [replaceConstLst, numConstsLst, *]
case case5 =>
intro c cs ih₁ ih₂
guard_hyp ih₁ :ₛ numConsts (replaceConst a b c) = numConsts c
guard_hyp ih₂ :ₛ numConstsLst (replaceConstLst a b cs) = numConstsLst cs
simp [replaceConstLst, numConstsLst, *]
theorem numConsts_replaceConst' (a b : String) (e : Term) : numConsts (replaceConst a b e) = numConsts e := by
apply replaceConst.induct (a := a)
(motive1 := fun e => numConsts (replaceConst a b e) = numConsts e)
(motive2 := fun es => numConstsLst (replaceConstLst a b es) = numConstsLst es)
<;> intros <;> simp [replaceConst, numConsts, replaceConstLst, numConstsLst, *]
theorem numConsts_replaceConst'' (a b : String) (e : Term) : numConsts (replaceConst a b e) = numConsts e := by
induction e using replaceConst.induct (a := a)
(motive2 := fun es => numConstsLst (replaceConstLst a b es) = numConstsLst es) <;>
simp [replaceConst, numConsts, replaceConstLst, numConstsLst, *]
end Term