PROPOSAL: language support for JSR 292
John.Rose at Sun.COM
Sat Mar 28 23:53:51 PDT 2009
Hello, colleagues. Here is a proposal which is linked to JSR 292
Here's the teaser (from my blog):
In order to work with dynamic types, method handles, and invokedynamic
I have made some provisional changes to javac as part of the Da Vinci
Machine Project. The mlvm wiki has a full description for Project
COIN. It is most desirable, of course, to program invokedynamic call
sites as Java expressions, not just ASM code, and that's what those
langtools patches are for.
The essential features are four:
• The type java.dyn.Dynamic will accept any method call and turn it
into an invokedynamic instruction, and the full range of such
instructions can be spelled from Java code.
• The type java.dyn.MethodHandle will accept any argument and return
types for a call to the method named invoke, which means that Java
code can spell the full range of method handle invocations.
• The full range of bytecode names acceptable to the JVM can be
spelled from Java code, using an exotic identifier quoting syntax.
• The type java.dyn.Dynamic serves as a bare reference type: Anything
implicitly converts to it, and it can be cast to anything, but it is
not a subtype of java.lang.Object. Its methods, of course, are those
from point #1, so it is handy for forming invokedynamic calls.
The rationale is pretty simple: If we put some minimal support into
Java for defining and using names in other languages, then Java can be
used as a system programming language for implementing them.
Otherwise, the system programming language will be assembled bytecode.
(I like to visit ASM, but don't want to live there.)
Do check out the wiki page; it has the full Project COIN proposal
-- John Rose (Da Vinci Machine Project)
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