> From: "Brian Goetz" <brian.go...@oracle.com>
> To: "Remi Forax" <fo...@univ-mlv.fr>
> Cc: "amber-spec-experts" <amber-spec-experts@openjdk.java.net>
> Sent: Thursday, April 7, 2022 11:24:05 PM
> Subject: Re: [External] : Re: Primitive type patterns
>> We already discussed those rules when we discuss instanceof, it means that "x
>> instanceof primitive" has different meaning depending on the type of x
> No, it does not. It means "does x match the pattern P" everywhere. It is
> pattern
> P is that has different meanings depending on type. This may sound like a
> silly
> distinction, but it is not! Pattern matching is inherently polymorphic -- it
> is
> all about reflecting dynamic conversions statically -- and exhibits the *same*
> polymorphism regardless of where it occurs.
The switch is (runtime) polymorphic while each patterns does not have to be
(statically) polymorphic.
If you prefer, i'm okay with be a pattern overriding polymorphic but not with a
pattern being overloading polymorphic (sometimes called ad-hoc polymorphism).
Your are proposing overloading of patterns, i.e the same pattern having
different meaning depending on the static types.
> And, why would we not want duality with:
> record R(short s) { }
> ...
> new R(x)
because new R(x) is alone while case R(...) is part of a larger set of
patterns/sub-pattern of the pattern matching, if for each pattern/sub-pattern,
we need a double-entry table to understand the semantics, we are well past our
complexity budget.
Rémi
