On 31/10/2020 23:30, Brian Goetz wrote:
On Oct 25, 2020, at 10:06 AM, Brian Goetz <brian.go...@oracle.com
<mailto:brian.go...@oracle.com>> wrote:
To make it clear that I'm not talking about the annoyance of typing
the cast, let's pretend I'm suggesting to write it like this:
BarImpl bi = (__static BarImpl) b;
Pulling on this string some more — I think there’s a connection
between this feature and total statement switches. We’ve been looking
for a way to make statement switches total, and here, what we’re
looking for is a way to make _casts_ total. Which suggests this is
one feature, not two. So perhaps:
switch-total (x) { … } // a switch, but with added bonus totality
checking
BarImpl b = (total BarImpl) bar // a cast, but with added bonus
totality checking
I agree the latter is a common enough problem when writing
implementation code where you have a sealed hierarchy and you know
there's only one impl (Foreign API has this all over the place).
To throw in the mix - how is some kind of pattern match assignment (we
referred to as a "let expression" in some of the earlier docs [1]) would
change the picture here? In other words, maybe it's overloading `=`
which is at odds here, and we need to make it more explicit that this is
more akin to an extraction/match?
Maurizio
[1] - https://cr.openjdk.java.net/~briangoetz/amber/pattern-semantics.html
Obviously we can use another word besides `total`, but it’s a pretty
good straw man.
