The attached patch should generate the desired error message. If
someone wants a test for this, just let me know which test file the
test belongs in and I will be happy to post an appropriate test for
that file.
--- a/src/classes/Positional.pir
+++ b/src/classes/Positional.pir
@@ -105,9 +105,24 @@ Returns a list element or slice.
.param pmc invocant
.param pmc argsblock
.param pmc options :slurpy :named
+
+ # if elements fails we can probably count on postcfix to err adequately
+ push_eh call_and_throw_err
$I0 = elements invocant
$P0 = box $I0
set_hll_global ['Whatever'], '$!slice', $P0
+ goto just_call
+
+call_and_throw_err:
+ .const string NO_ELEMENTS_MARKER = "elements() not implemented"
+ .get_results ($P0)
+ $I0 = length NO_ELEMENTS_MARKER
+ $S0 = $P0
+ $S0 = substr $S0, 0, $I0
+ if $S0 == NO_ELEMENTS_MARKER goto just_call
+ rethrow $P0
+
+just_call:
.local pmc args
args = argsblock()
args = 'list'(args)
