`linter.unusedVariables` false positive when using `match` and `assumption`

[TwoFX]

Prerequisites

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• [x] Check that your issue is not already filed: https://github.com/leanprover/lean4/issues
• [x] Reduce the issue to a minimal, self-contained, reproducible test case. Avoid dependencies to Mathlib or Batteries.
• [x] Test your test case against the latest nightly release, for example on https://live.lean-lang.org/#project=lean-nightly (You can also use the settings there to switch to “Lean nightly”)

Description

The unusedVariables linter reports a false positive on the theorem bad below:

inductive A where
  | intro : Nat → A

def A.out : A → Nat
  | .intro n => n

/--
warning: unused variable `h`
note: this linter can be disabled with `set_option linter.unusedVariables false`
-/
#guard_msgs in
theorem bad (n : A) (i : Nat) (h : i ≤ n.out) : i ≤ n.out :=
  match n with
  | .intro _ => by assumption

#guard_msgs in
theorem good₁ (n : A) (i : Nat) (h : i ≤ n.out) : i ≤ n.out := by
  cases n with
  | intro n => assumption

#guard_msgs in
theorem good₂ (n : A) (i : Nat) (h : i ≤ n.out) : i ≤ n.out := by
  assumption

#guard_msgs in
theorem good₃ (n : A) (i : Nat) (h : i ≤ n.out) : i ≤ n.out :=
  match n, h with
  | .intro _, h => by assumption

-- Bodies of `bad` and `good₃` are identical:

/--
info: theorem bad : ∀ (n : A) (i : Nat), i ≤ n.out → i ≤ n.out :=
fun n i h =>
  match n, h with
  | A.intro a, h => h
-/
#guard_msgs in
#print bad

/--
info: theorem good₃ : ∀ (n : A) (i : Nat), i ≤ n.out → i ≤ n.out :=
fun n i h =>
  match n, h with
  | A.intro a, h => h
-/
#guard_msgs in
#print good₃

Context

There are several other issues about false positives of the unusedVariables linter. I have checked them and I believe that this is a new issue.

Steps to Reproduce

1. Copy the code above into the Lean web editor

Expected behavior: Linter should not warn about bad

Actual behavior: Linter warns about bad

Versions

4.11.0-nightly-2024-07-09 on the Lean web editor

Impact

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