stack-replacement.txt

#!/usr/bin/env perl6

# Stolen from https://docs.perl6.org/language/functions#sub_nextwith
# and annotated with line numbers

proto a(|) {*}

multi a(Any $x) {
  say "Any $x";
  say "This is Any L$?LINE";
  unless $x {
    die "ouch";
  }
  return 5;
}
multi a(Int $x) {
  say "Int $x";
  say "This is Int L$?LINE";
  nextwith($x + 1);
  say "never executed because nextsame doesn't return";
}

a(-1);

# OUTPUT:
# Int -1
# This is Int L18
# Any 0
# This is Any L10
# ouch
#   in sub a at /tmp/stack-replacement line 12
#   in sub a at /tmp/stack-replacement line 19
#   in block <unit> at /tmp/stack-replacement line 23
#
## If nextwith were stack-replacing, we should only get two lines of
## backtrace, not three