Draft: test: Add test for #301?

[alt-romes]

If we use an arbitrary computation as the value for a DebugView field,
which is re-created from scratch everytime we recompute that DebugView
fields, then evaluating that thunk is not persisted across refreshing
the variable.

Every time we re-fresh the variable we re-create the thunk, so it makes
some sense that forcing it is not persisted across re-freshing, but
still a bit unsatisfactory (esp. since the variables are invalidated as
soon as a variable is forced, so we only see a flash of these values)

See #301

[alt-romes]

Maybe this shouldn't be considered unexpected behavior.

Would the user ever want these fields to be lazy? I guess if we don't want to do the work straight away but still have the option to display on force would be useful.

However, that means we'd need a way of persisting the value across invocations. Potentially by extending Program to allow explicitly allocating a re-usable value at a given key.

See #301 (comment)

[alt-romes]

I now think we should just accept that a VarFieldValue of a value always computed from scratch must be forced to display properly, otherwise it's just going to do the uniform thing which is display the right hand side as a thunk. And every time we load it again we see the thunk again as it's not preserved anywhere. That is the "natural" let's uniformly observe the value that VarFieldValue wraps directly

See the comments on #301