Syntactic Closures vs. syntax-case
On this
page about syntactic closures, we see the definition of an
anaphoric-if macro that doesn't transmit the "it" binding to the
alternative clause — just to the consequent. This is pretty
sophisticated. I immediately began to think about how you could do the
same with syntax-case (as clearly others
had before me) and it turns out to actually be easier. The only
real downside is the introduction of another binding — but of
course the mythical Sufficiently Smart Compiler will optimise that
away immediately anyway.