Cannot use hole for context proof in match

[MrQubo]

Prerequisites

Please put an X between the brackets as you perform the following steps:

• Check that your issue is not already filed:
  https://github.com/leanprover/lean4/issues
• Reduce the issue to a minimal, self-contained, reproducible test case.
  Avoid dependencies to Mathlib or Batteries.
• 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

This code doesn't work:

def last {α : Type} (a : Array α) : Option α :=
  match _ : a.size with
  | 0 => none
  | m + 1 => some a[m]

but works when explicitly naming proof:

def last {α : Type} (a : Array α) : Option α :=
  match h : a.size with
  | 0 => none
  | m + 1 => some a[m]

Context

Hole works with if-then-else:

def last {α : Type} (a : Array α) : Option α :=
  if _ : a.size = 0
    then none
    else some a[a.size-1]

For consistency should also work with match.

Versions

Lean 4.16.0-nightly-2025-01-23

Impact

Add 👍 to issues you consider important. If others are impacted by this issue, please ask them to add 👍 to it.

[nomeata]

Thanks for reporting, I certainly have been hitting this myself