On 04/28/2015 03:05 PM, Paul Sandoz wrote:
[...]
I do understand the desire to control methods, but API design isn't
just about minimalism, it is also about meeting common use cases in a
natural way. The parallel is of course a standard if (obj instanceof
Foo) statement in Java, where developers often curse that they have to
additionally cast obj after the check.
I believe Ceylon might also do contextual type narrowing. I dunno how easy it
would to modify the Java language and javac to do similar things. A separate
discussion to be had...
I think this was discussed on the coin project mailing list when talking
about the precise re-throw of exception.
The main issue is that a more precise type will select another overload
than the one that javac currently select:
class A {}
class B extends A {}
class Bar {
void foo(A a) { ... }
void foo(B b) { ... }
}
Let suppose we have this code:
A a = ...
if (a instanceof B) {
foo(a);
}
without narrowing, it will call foo(A), with narrowing, it will call foo(B).
Rémi
