From @masak

<PerlJam> It would be nice if multi-dispatch errors has a little more
awesomeness.
<PerlJam> It lists the candidates' signatures, but not what it's
trying to match against those signatures.
<masak> indeed. I've had the same thought.
<PerlJam> jnthn​: How hard would it be to add the capture of the
sub/method being matched against candidates in multi-dispatch when it
fails?
<jnthn> We could. (more)
<jnthn> I'm just a little scared what happens if that evaluation goes explodey.
<jnthn> For <handwaving> reasons, it may be tricky to be robust in that case.
<jnthn> We could easily try it though.
<masak> \o/
<jnthn> oh, akshually, I can think of an OK way to do it.
<jnthn> Best is to file a ticket suggesting it.
* masak submits rakudobug

From @Mouq

02​:23 < Mouq> There aren't any specific examples given for #​78670... can we consider it closable with tests?
02​:23 < synopsebot> Link​: https://rt-archive.perl.org/perl6//Public/Bug/Display.html?id=78670
02​:24 < Mouq> m​: multi foo(Int $x, Str $b) {}; my $a = "bcd"; foo $a
02​:24 <+camelia> rakudo-moar 070196​: OUTPUT«===SORRY!=== Error while compiling /tmp/sguTFCxzau␤Calling 'foo' will never work with argument types (Mu)␤
  Expected any of​: ␤ :(Int $x, Str $b)␤at /tmp/sguTFCxzau​:1␤------> foo(Int $x, Str $b) {}; my $a = "bcd"; ⏏foo $a␤»
02​:25 < Mouq> m​: multi foo(Int $x, Str $b) {}; my $a = "bcd"; foo $a, "bar"
02​:25 <+camelia> rakudo-moar 070196​: OUTPUT«Cannot call 'foo'; none of these signatures match​:␤​:(Int $x, Str $b)␤ in sub foo at /tmp/S66ShGWzau​:1␤ in block
  <unit> at /tmp/S66ShGWzau​:1␤␤»
02​:25 < Mouq> Ahh, it just seems to be errors the compiler can catch early
02​:25 < Mouq> I'll add this to the ticket

To clarify, the first example has a good error. The second doesn't include information about why it failed to find a matching signature, and thus is still LTA.

On Thu Oct 28 09​:36​:37 2010, masak wrote​:

<PerlJam> It would be nice if multi-dispatch errors has a little more
awesomeness.
<PerlJam> It lists the candidates' signatures, but not what it's
trying to match against those signatures.
<masak> indeed. I've had the same thought.
<PerlJam> jnthn​: How hard would it be to add the capture of the
sub/method being matched against candidates in multi-dispatch when it
fails?
<jnthn> We could. (more)
<jnthn> I'm just a little scared what happens if that evaluation goes
explodey.
<jnthn> For <handwaving> reasons, it may be tricky to be robust in
that case.
<jnthn> We could easily try it though.
<masak> \o/
<jnthn> oh, akshually, I can think of an OK way to do it.
<jnthn> Best is to file a ticket suggesting it.
* masak submits rakudobug

The RT System itself - Status changed from 'new' to 'open'

From @Mouq

On Tue Mar 03 18​:27​:45 2015, Mouq wrote​:

02​:23 < Mouq> There aren't any specific examples given for #​78670...
can we consider it closable with tests?
02​:23 < synopsebot> Link​:
https://rt-archive.perl.org/perl6//Public/Bug/Display.html?id=78670
02​:24 < Mouq> m​: multi foo(Int $x, Str $b) {}; my $a = "bcd"; foo $a
02​:24 <+camelia> rakudo-moar 070196​: OUTPUT«===SORRY!=== Error while
compiling /tmp/sguTFCxzau␤Calling 'foo' will never work with argument
types (Mu)␤
Expected any of​: ␤ :(Int $x, Str $b)␤at
/tmp/sguTFCxzau​:1␤------> foo(Int $x, Str $b) {}; my $a = "bcd"; ⏏foo
$a␤»
02​:25 < Mouq> m​: multi foo(Int $x, Str $b) {}; my $a = "bcd"; foo $a,
"bar"
02​:25 <+camelia> rakudo-moar 070196​: OUTPUT«Cannot call 'foo'; none of
these signatures match​:␤​:(Int $x, Str $b)␤ in sub foo at
/tmp/S66ShGWzau​:1␤ in block
<unit> at /tmp/S66ShGWzau​:1␤␤»
02​:25 < Mouq> Ahh, it just seems to be errors the compiler can catch
early
02​:25 < Mouq> I'll add this to the ticket

Current behavior​:

06​:41 <Mouq> m​: multi foo(Int $x, Str $b) {}; my $a = "bcd"; foo $a
06​:41 <camelia> rakudo-moar dfad9c​: OUTPUT«===SORRY!=== Error while compiling /tmp/77JmpQrCM7␤Calling foo(Mu) will never work with any of
  these multi signatures​:␤ (Int $x, Str $b)␤at /tmp/77JmpQrCM7​:1␤------> foo(Int $x, Str $b) {}; my $a = "bcd"; ⏏foo $a␤»
06​:41 <Mouq> m​: multi foo(Int $x, Str $b) {}; my $a = "bcd"; foo $a, "bar"
06​:41 <camelia> rakudo-moar dfad9c​: OUTPUT«Cannot call foo(Str, Str); none of these signatures match​:␤ (Int $x, Str $b)␤ in sub foo at
  /tmp/e5lT9TVHuv​:1␤ in block <unit> at /tmp/e5lT9TVHuv​:1␤␤»

A test was added in Roast commit d4b9bb80940d8.

Closing this ticket as resolved :)

~Mouq

@Mouq - Status changed from 'open' to 'resolved'