internal/core/adt: add tests for Issue 3972
Issue #3972
Signed-off-by: Marcel van Lohuizen <mpvl@gmail.com>
Change-Id: I982cea1cd898f4003e289720276d20b34f853824
Reviewed-on: https://review.gerrithub.io/c/cue-lang/cue/+/1217126
TryBot-Result: CUEcueckoo <cueckoo@cuelang.org>
Unity-Result: CUE porcuepine <cue.porcuepine@gmail.com>
Reviewed-by: Daniel Martí <mvdan@mvdan.cc>