hg: amber/amber: hooking records to patterns
brian.goetz at oracle.com
Fri Apr 6 19:58:52 UTC 2018
You're forgetting field accessor method handles. You can express
Foo::list as a field getter method handle, but then it has a return type
of ArrayList. You'd have to asType it to express it with a return type
of List. Its easy to represent a direct MH in the CP; its harder
(though we can do it now) to represent an asType MH in the CP.
Besides, stable interfaces are a good thing. (I could try and infer a
method return type at runtime by analyzing its bytecode, but its better
if the method says "I return List". Same basic deal; the component MHs
On 4/6/2018 3:52 PM, forax at univ-mlv.fr wrote:
>> and we have a pattern that yields a binding variable of type `List`. If
>> the component MH were Foo::list, it would (a) yield the wrong type, and
>> (b) the type might be unstable if the implementation were to change.
>> Having a stable descriptor for what the pattern yields as bindings as
>> separate from the implementation for how to produce those bindings is
>> necessary for stability.
> All the problems of type you can have are true not only for the extractor but also for the getter/component method too,
> so if you already the right type encoded in the component method, you do not need to provide the same information as a descriptor.
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