Plain GROUP! & Branching: Only Run If Branch Taken?

[hostilefork]

@hostilefork

My intuition is still that not running groups unless the branch is going to be taken is the more useful behavior. But... when you look at the available parts, the cleanest way to provide both capabilities is to say that the plain GROUP! evaluates unconditionally... and the THE-GROUP! only runs if the branch runs.

As it turns out, there's no real choice but to run the groups unconditionally now.

Changing escapable literals to use plain groups means that so long as branching structures use escapable literals for the branch, then groups will execute unconditionally and typecheck the result.

Changing away from escapable literals to use non-escapable ones would break the ability to get implicit tiebreaking and you couldn't use lambdas on the right of things like THEN and ELSE without putting them in groups.

Going away from literal arguments for branches altogether would kill off soft-quoting branching

So if there's going to be a form of branch that doesn't calculate a synthesized branch unless the branch is going to be taken... I think THE-GROUP! is the answer.