List.filterMapM is backwards

[ChiCubed]

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

List.filterMapM works from right to left, not left to right as the documentation claims.

-- for reference. output: 123
#eval discard $ [1, 2, 3].mapM fun x => IO.print x

-- expected: 123, actual: 321
#eval discard $ [1, 2, 3].filterMapM fun x => some <$> IO.print x

Versions

"4.11.0-nightly-2024-07-07" on live.lean-lang.org

Additional information

I tested these other monadic map-like functions and they all seem to behave as advertised:

• List: mapM, forM, filterM, filterRevM, foldlM, foldrM
• Array: the above (except Array.filterRevM which doesn't exist) and, notably, filterMapM

Impact

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