Crash when attempting toMSet on list comprehension

[jwatts-maybe]

As a minimal example, running Conjure on something like

find x : mset (maxSize(5)) of int(0..5)
such that x = toMSet([i | i <- [1,2,3]])

results in the bug message.

Repo version: 03d6014e5 (2024-09-25 19:47:19 +0100)

Error message:

Not refined: x
Domain     : mset {ExplicitWithFlags} (maxSize 5) of int(0..5)
    Context #1: x = toMSet([1, 2, 3; int(1..3)])

CallStack (from HasCallStack):
  error, called at src/Conjure/Bug.hs:17:15 in conjure-cp-2.5.1-3ow97tapNr9FQhaVki9Yr3:Conjure.Bug
  bug, called at src/Conjure/UI/Model.hs:1036:26 in conjure-cp-2.5.1-3ow97tapNr9FQhaVki9Yr3:Conjure.UI.Model

It's slightly unclear whether it is supposed to be possible to do this, but the equivalent with toSet works fine, and at least it should probably be rejected as incorrect Essence.