On Wed, 23 Aug 2017 06:20:49 -0700, b...@abrij.org wrote:
> On Mon, 24 Jul 2017 10:04:54 -0700, c...@zoffix.com wrote:
> > The coercion works fine here:
> >
> > 17:03 Zoffix m: class B {…}; class A { method B { B.new }}; class
> > B
> > {}; sub foo(B() $b) { say "hi" }; foo(A.new)
> > 17:03 camelia rakudo-moar 2fb8c7: OUTPUT: «hi?»
> >
> > But if I add `:D` smiley, it fails:
> >
> > 17:03 Zoffix m: class B {…}; class A { method B { B.new }}; class
> > B
> > {}; sub foo(B:D() $b) { say "hi" }; foo(A.new)
> > 17:03 camelia rakudo-moar 2fb8c7: OUTPUT: «Type check
> > failed
> > in binding to parameter '$b'; expected B but got A (A.new)? in sub
> > foo at <tmp> line 1? in block <unit> at <tmp> line 1??»
> >
> > https://irclog.perlgeek.de/perl6/2017-07-24#i_14915397
>
> Seems to be more generic than custom classes:
>
> $ perl6 -e 'sub foo(Int() $b) { say $b }; foo("42")'
> 42
> $ perl6 -e 'sub foo(Int:D() $b) { say $b }; foo("42")'
> Type check failed in binding to parameter '$b'; expected Int but got
> Str ("42")
> in sub foo at -e line 1
> in block <unit> at -e line 1
>
> This raises the spec question, should e.g. IO:U($a) try to convert $a
> to an IO,
> and if that succeeds, succeed the bind with the type object of
> whatever doer (or
> subclass were IO a class) of IO which resulted? Or fail the bind?
> The latter is
> more consistent with the above desired behavior... but does
> "Class:D()" mean
> coerce-to-then-check-definedness, or go-all-out-to-make-a-defined-
> value?
>
> This doesn't make much sense yet either:
>
> $ perl6 -e 'Int:D(4).say'
> (Int:D)
This ticket and RT#126433 can be combined.
