+1.
On 10/6/2017 7:51 AM, Tagir Valeev wrote:
Hello!
As for throw, I think it should just be converted to an expression,
probably of the same type as a null literal (thus throw statement will
become an expression statement). In this case it could be useful not
only in lambdas, like:
return list.isEmpty() ? throw new NoSuchElementException() : list.get(0);
I believe, it was discussed in context of pattern matching.
With best regards,
Tagir Valeev.
On Fri, Oct 6, 2017 at 6:16 PM, Remi Forax <[email protected]> wrote:
Hi all,
The JEP 302 list some improvements but I think some are missing, obviously,
it's up to debate :)
So here is my list of left leftovers:
- support throw statement as a lambda expression
I think we have already discussed informally about this one.
The compiler should allow to have a lambda expression that starts with throw.
so a code like this will become valid
merge(key, value, (_, _) -> throw new IllegalStateException("key " + key + "
already present));
- allow void to be converted to Void (by returning null)
This proposal is perhaps more controversial, currently there is no way to
simply convert a lambda statement to a lambda expression.
So a code like will compile
<T, R> R sync(T initial, Function<? super T, ? extends R> fun) {
synchronized(lock) {
return fun.apply(initial);
}
}
Consumer<String> c = System.out::println;
sync("foo", c::accept); // the compiler should generate a synthetic
static method that returns null
This proposal is problematic because:
- it implicitly produces a null, which is a bad idea
- if there are several overloads, a lambda statement can now match more
methods so the compiler may reject code that was previously working or worst
call another method that the one that was originally selected.
The other question is should the conversion be extended to work with non
lambda code,
i.e. consider that 'return' or an implcit 'return' can be trasformed to a
return null by the compiler.
Void m() {
return; // the compiler generates return null;
}
Void m() { } // the compiler generates return null;
On the positive side, it mix well with the switch expression proposed in the
Pattern Matching JEP.
Supplier<Void> supplier =
() -> switchexpr(someValue) {
case 0 -> System.out.println("foo");
default -> { /* empty */ }
};
regards,
Rémi
[1] http://openjdk.java.net/jeps/302
