I just read through https://github.com/rakudo/rakudo/issues/4878 and I had a thought.
It's like the "where" clause has its own signature-like list of types it will accept. When the where clause uses the default topic "$_" then that topic has no constraint, and MAIN can probe if "--dir=something" should be interpreted as a flag *Bool::True* or if it should be the string *"something"*. When the "where" clause has only $dir in the body, the optimizer can specialize it to only take Str, and then MAIN doesn't need to probe the *Bool::True *case. Haven't looked at the source, I'm guessing. -y On Sat, Apr 16, 2022 at 11:49 AM Luca Ferrari <fluca1...@gmail.com> wrote: > On Fri, Apr 15, 2022 at 4:15 PM yary <not....@gmail.com> wrote: > > > > Here's how I ended up handling input arg validation, with meaningful > error messages, as part of a Perl Weekly Challenge a couple years ago. It > looks almost the same as Luca's original, except mine uses "die" instead of > "warn", which means it won't attempt to continue once it encounters a bad > arg. > > Interesting, but I used `warn` because I want to display all things > that are not correct at once. In the test case I submitted there is no > great difference in using warn instead of die, since the program > should stop in any case, but if you have a bunch of named arguments I > would like to see all `warn` messages at once, so I have a chance to > fix all my invocation line at once. > > > I'm starting to think Luca's found a regression, since using the > explicit variable name instead of the topic fixes the issue. That seems > wrong. > > I don't know, in the beginning I thought there was a problem with the > language specifcation, I mean, something has changed in the `wherre` > and topic usage. However, hoping to improve our knowledge or the > implementation, I've submitted an issue here > <https://github.com/rakudo/rakudo/issues/4878>. > > Thanks, > Luca >
