trySuggestions (exact? etc.) can produce wrongly indented source

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

The result of clicking "Try this" after an exact? gives "type mismatch" and "unexpected identifier; expected command" errors.

theorem AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA :
    True → True → 1 = 2 := by 
  sorry

theorem test : 1 = 2 := by exact?

live.lean-lang.org version

Context

A student encountered this when using exact? on mathlib.

Steps to Reproduce

1. Code as above
2. Click the try this suggestion from exact?

Expected behavior: The result of exact? should close the goal.

Actual behavior: The result of exact? gives two errors, both of which are unhelpful to beginners.

Versions

Using live.lean-lang.org:
Lean 4.16.0-nightly-2025-01-10
Target: x86_64-unknown-linux-gnu

Impact

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Start with the minimal reproduction in the issue and reproduce it on the Lean nightly version; the reported failure occurs after clicking “Try this” for exact?. Compare the generated suggestion with the expected goal-closing behavior, then verify that using it no longer produces the reported type-mismatch and unexpected-identifier errors.