[racket-dev] [racket] keyword args static checking and optimization

At Mon, 8 Aug 2011 10:12:36 -0500, Robby Findler wrote:
> >   Another possibility is to redirect the `set!' on `f' to the
> >   underlying `proc', and somehow make the optimized call to `core'
> >   happen only when `proc' is never mutated. Due to the order of macro
> >   expansion, whether `f' is mutated is not necessarily known when a
> >   call to `f' is expanded. The expansion of a call to `f' would have
> >   to embed the condition that `proc' is not mutated.
> 
> How about adding an extra indirection? That is, you can have core be a
> simple wrapper function that calls some other function, and have proc
> also call that. Then the set! can be redirected to this thing that
> both call (you'd probably have to wrap the right hand side of the set!
> in some kind of argument protocol adjustment thing but if we're
> set!'ing procedures maybe we should have to pay for that).

A use of `f' in a position other than an application position expands
to just `proc'. If `f' is mutated to something other than a procedure,
those uses of `proc' need to see the new value, so `proc' cannot be a
wrapper.

I considered redirecting a mutation of `f' to both `proc' and `core',
but I worry about turning an atomic assignment operation into two
steps.

A non-application use of `f' could expand to `(get-f)' instead of
`proc', and maybe there's a way for a single assignment to adjust both
`core' and `(get-f)', but I don't quite see it --- at least not without
destroying the direct use of `core' that enables inlining in common
cases.