RFR: implementation for JEP 334: JVM Constants API
jbvernee at xs4all.nl
Fri Jun 1 13:04:32 UTC 2018
(Thanks, Brian, for your earlier response. I've been interested in the
constants API/condy/constant propagation since first hearing about it
last year, so it's great to be able to get involved :)
I have some more code review comments. This time I looked at the
implementations as well. I hope it's okay for a non-member to give
comments about that, but after writing them down I didn't want to just
throw them away.
They're organized by file:
- For `arrayType()` you can change it to return `Class<T>` (useful for
reflection), which is a valid sub-signature. (I mentioned this before,
but it seems to have fallen through the cracks)
- For `EnumDesc.constantBootstrap` I think you can require a `ClassDesc`
directly as a parameter instead of a descriptor string that you then
have to convert to a ClassDesc? (When you use it in `describeConstable`
you have to convert your ClassDesc to a descriptor string. It'd be
simpler if you could just pass the ClassDesc)
- For `VarHandleDesc.Kind.toBSMArgs` you could change it to return a
`ConstantDesc<?>`, since the only use case requires an array. (also,
see the next comment)
- In `VarHandleDesc.describeConstable` you can use `Constable<?> args
= kind.toBSMArgs(declaringClass, constantName(), varType)` (assuming the
changed return type), instead of having the ternary.
- In the different `describeConstable` maybe use `orElseThrow()` instead
of `get()` on the optionals. (I think get() will be deprecated soon?)
- For the last one (line 662), instead of doing an explicit `isPresent`
check, you can also use `Optional::map`: `return
arrayTypeRef.map(VarHandleDesc::ofArray);`. (If it's ok to use indy
- Some of the string manipulation going on with descriptor strings looks
kinda cryptic (for instance, several places use `descriptor.length() ==
1`, instead of a more descriptive function call, e.g.
`isPrimitveDescriptor(descriptor)`). It might be a good idea to factor
out the nitty gritty string manipulation into a DescriptorStrings class
as static helpers, and use static imports (I don't know if that exists
in the JDK, but there seems to be a wide demand for it).
- In `arrayType(int)`, add an exception message here. e.g.: `"rank must
be positive, but was: " + rank`.
- In the constructor, I suggest factoring out the if-condition to an
`isReferenceDescriptor(String descriptor)` helper. (more descriptive)
- In `resolveConstantDesc` (line 77): You can use `if(c.isPrimitive())`
instead of `c.descriptorString().length() == 1`
- In the same method (line 82): You can use `clazz = clazz.arrayType()`
instead of `clazz = Array.newInstance(clazz, 0).getClass();`
- The `resolveArgs` method uses an odd dance to propagate the exception
thrown from the lambda, imho it's better to just use a traditional
for-loop here instead of the stream.
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