Syntax for Subverting Virtual Binding

[hostilefork]

@hostilefork

The more general rule is that whatever it is you quote gets unquoted by one level...the LET assumes the quoted thing is not for its consumption, but for whatever is going to be consuming the SET-BLOCK! later. That could be a multi-return, or anything else that left-quotes SET-BLOCK!s.

I'll point out that this is yet another defeat to the idea of using a BLOCK! the state for single-stepping.

let [x 'y]: whatever

If you single step, the LET will create a virtual binding for X and leave Y alone. Then LET itself vanishes. What remains is:

[x y]: whatever  ; with virtual binding on x

If the evaluator is limited to having to return the state in terms of a position in the original block, it wouldn't have the option of giving this back as the state for the next step... since there is no [x y]: there. Just [x 'y]:

My feeling is that the evidence is pretty strong on the side of saying evaluator state should be more flexible than a BLOCK!. We must keep looking at how to empower code that needs to single-step (I've described ASSERT and TLS EMIT) but accept that what comes back is a FRAME! and not the previous simplistic BLOCK! of a position that the historical DO/NEXT had.