Subject: Re: no implicit conversions for member selections like this.x?
Newsgroups: gmane.comp.lang.scala
Date: 2006-04-13 16:43:02 GMT (3 years, 11 weeks, 6 days, 8 hours and 34 minutes ago)
Adriaan Moors wrote:
> Hi,
>
> I think I may have encountered a bug or at least a limitation in
> implicit conversions and I was wondering why this is so. It seems
> implicit conversions are only inferred for member selections with an
> explicit target object, different from |this|, such as |a.foo| and not
> when the target object is |this| or when it is left implicit.
>
Thanks for this observation. Indeed a view is not searched when the
method name is a simple identifier. I still have to find out why no view
is found when the prefix is `this'. In any case, I think you are right
that we should correct this, so I classify these things as bugs.
Cheers
-- Martin
> I've tried to construct a small example that exhibits the same
> behaviour as in my actual code (which uses implicit conversions to
> insert the unrolling and rolling operations that witness the
> isomorphism between a recursive type and its unrolling).
>
>
> implicit def foo2bar(foo :Foo) :Bar = foo.bar
>
> class Foo(val bar :Bar) {
> def testCoercion ={ val a = this; a.baz /* here, foo2bar is
> inferred by the compiler, as expected */}
> def testCoercionThis = baz // --> error: not found: value baz
> def testCoercionThis = this.baz // --> error: value baz is not a
> member of Foo
> }
>
> class Bar { def baz = System.out.println("baz")}
>
>
> Obviously, this is a contrived example, but it would really be useful
> in my actual code (see my earlier post http://article.gmane.org/
> gmane.comp.lang.scala/1956/match=hodgp and http://www.cs.kuleuven.be/
> ~adriaan/?q=hodgp_scala
> I'm trying to get rid of |Fix()| and the indirection via the |out|-
> member, which would largely make up for the lack of recursive type
> synonyms).
>
> I guess this could also be used to implement a kind of poor man's
> forwarding.
>
> regards,
> adriaan
>