Lean can't understand field notation inside a lambda inside a match arm

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 fails to type check:

#check match () with | _ => [0].map (·.toInt8)

Context

None.

Steps to Reproduce

See this code at https://live.lean-lang.org/#project=lean-nightly&codez=MQYwFgpiDWAEC2BDALuWAKAlLA7gS2TFgB9YB9WAXgD5YBtABgF0A6JABwwHaXkB7AJIA7ZAA5MQA

Expected behavior: This code passes type check.

Actual behavior:

invalid field notation, type is not of the form (C ...) where C is a constant
  x✝
has type
  ?m.79

Versions

4.16.0-nightly-2024-12-12

Additional Information

None.

Impact

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Start by reproducing the minimal snippet #check match () with | _ => [0].map (·.toInt8) on the Lean nightly release using the linked Live Lean test case. Investigate field-notation elaboration when the lambda appears inside a match arm. Done means the snippet passes type checking without the reported invalid-field-notation error.