Value.value can't be used in a pure test

[ceedubs]

The Value.value builtin can't be used in a test. Is this intended? It doesn't declare the IO ability, but the error message indicates that it is performing IO.

fresh/main> builtins.merge

  Done.

foo : [Test.Result]
foo =
  _ = Value.value 3
  [Result.Ok "passed"]

  Loading changes detected in scratch.u.

  I found and typechecked these definitions in scratch.u. If you
  do an `add` or `update`, here's how your codebase would
  change:

    ⍟ These new definitions are ok to `add`:
    
      foo : [Result]

fresh/main> add

  ⍟ I've added these definitions:

    foo : [Result]

fresh/main> test

🛑

The transcript failed due to an error in the stanza above. The error is:

💔💥

I've encountered a call to builtin.bug with the following value:

  "pure code can't perform I/O"

Stack trace:
  builtin.bug
  #iqsghdla6m

Environment (please complete the following information):

• ucm --version 0.5.31

[aryairani]

Here's the spot where that's defined.

unison/unison-runtime/src/Unison/Runtime/Builtin.hs

Line 1674 in d3dea93

("Value.value", (Tracked, value'create)),

[ceedubs]

I'm not sure whether the right fix is to change Value.value to not be Tracked or to keep it Tracked but allow it in the test/doc sandboxes. The latter seems like the safer change.

[pchiusano]

Probably the latter.

This should be allowed within Unison Cloud’s sandbox as well, it’s useful sometimes if you’re doing custom hashing or serialization of generic values.