This is the mail archive of the
kawa@sourceware.org
mailing list for the Kawa project.
Re: wildcards in parameterized types?
On Oct 6, 2011, at 9:16 PM, Per Bothner wrote:
On 10/06/2011 04:32 PM, Jamison Hope wrote:
On Oct 6, 2011, at 2:59 PM, Per Bothner wrote:
I think that's only part of it. The first thing IMO to "fix"
is the type of com.example.SomeClass, so that it is (in Kawa syntax)
java.lang.Class[com.example.SomeClass] so the type matches the
type of the Java expression com.example.SomeClass.class.
Presumably the ParameterizedType instance would be coerced to the
correct type when passed to a function expecting a Class instance.
Careful. I think you're mixing reflective levels here,
Yeah, probably.
The expression java.lang.Object evaluates to a *value* which
the same as the Java expression java.lang.Object.class
(or Class.forName("java.lang.Object")). This will not change.
What should is the *compile-time type* of the expression.
I.e. when given the QuoteExp that represents java.lang.Object,
what will getType() return? Will it return a ClassType
as today (Specifically Type.javalangClassType) or will it
return a ParameterizedType instance? The latter seems correct,
but does not change the runtime value or how it is coerced.
OK, I think I get it now. So the *value* of the literal
java.lang.Object will continue to be java.lang.Object.class, but
the *type* will be java.lang.Class[java.lang.Object]. Which is
not saying that the literal java.lang.Object will mean the same
as the literal java.lang.Class[java.lang.Object] (which is of type
gnu.bytecode.ParameterizedType).
Anyway, as far as wildcards go, I don't have any good suggestions
for good syntax to cover all the cases. Foo<?> => Foo[?] seems
natural, and Foo<? extends Super> => Foo[Super?] seems sensible,
but what to do about Foo<V extends Super> (which binds V to a type),
or Foo<? super Sub>... I don't know. What do other JVM languages
do (Scala, Clojure, ...)?
--
Jamison Hope
The PTR Group
www.theptrgroup.com