> bar returns nothing, how could you echo it. I see nothing to fix here,
> especially not the involved lengths.
if nim treated a void-returning function call as being 0 arguments as in D (as
if no argument was passed) then there would be no call to echo (ie, fun(bar())
would call bar() and then fun()) ; this introduces less edge cases (no need to
consider void variables). Maybe I'm missing some valid use case I haven't
thought about?
> I guess that D has implemented some kind of SFINAE that won't run for args
> that cause errors?
no, it's simpler than that: as I was explaining above, in D, variadic argument
size will be 0 when calling fun(bar()); since bar returns void
isn't that a better behavior? if not what would be downsides of that?
> it doesn't need those sorts of things, but you can certainly emulate the
> behavior.
your code doesn't work, compiles(echo(x)) still returns true; here's a full
modified example so you can click run:
import macros
import typetraits
import strformat
macro fun*(n: varargs[untyped]): typed =
result = newNimNode(nnkStmtList, n)
var echoedCount = 0
for x in n:
if compiles(echo(x)):
result.add(newCall("echo", x))
echoedCount += 1
result.add(newCall("echo", newStrLitNode($(echoedCount))))
proc bar() = echo "ok"
fun(1+1) # n.len=1
fun() # n.len=0
# comment this to make it work
fun(bar())
