What can we improve in JSR292 for Java 9?

[Mark Roos]

Julian wrote
        An open question that I have is that of facilitating the support 
of overloaded methods. 
        It's typically something dynamically-typed languages struggle 
with, and doing it 
        correctly *and* efficiently is not that pretty.

Overloaded and multi methods have always been an interesting topic for me. 
 I see two parts to this, the
dispatch decision code and the view the programmer sees when coding.  Of 
these the later seems to be
the most difficult to envision in a object oriented dynamic language. This 
issue I see is that usually its not
for a single type but for a family of types ( hierarchy) causing the 
pattern match to explode or the use of
an isaFoo methods as part of the match.

Another use would be in specialization of a call site based on argument 
types, perhaps using something like Truffle
or LLVM jit to generate a specialized path.  In this case one would want 
an efficient GWT which could pattern
match on some instance var of each argument on the stack.  There would 
probably only be a few of these per
call site so one could do this today with a tree of GWTs and a pattern 
match test.

So once again an efficient compiler/optimizer for GWT constructs would 
help along with counters and an handle
to invoke to do the optimization.  I share some other's concerns on 
performance impact of this. 

Perhaps the solution is to have a means to build an efficient GWT using 
Panama.

regards
mark
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