Creating a clone of a javac.code.Type

[Werner Dietl]

Jon, Joel, all,

Steve noticed that CheckExamples was misbehaving on a test case. I
investigated this and found that this is related to the problem
previously raised by Bhavesh: there is unwanted sharing between Type
instances and having a type annotation on one Type results in type
annotations on others.

The CheckExamples test that failed was CantAnnotateStaticClass, which
turns out to be the only test case that was using Types for it's
logic.
Recent refactorings initialize the type annotations later and this
test case failed.
I moved the corresponding check and added an extra test case that more
directly highlights this issue.

However, I don't know what the best solution to the sharing issue is.

In previous discussions (sorry, before the mailing list existed;
thread "JSR 308 patch discussion: cloning of Type" from September 15,
2011) we came to the conclusion that cloning Type instances was bad
and removed the feature:

http://code.google.com/p/jsr308-langtools/source/detail?r=48559298cf51c1a0143b25509ae04a4cd0b640ac

At that point we didn't have the CantAnnotateStaticClass test case and
no JavaDoc tests - therefore, all jtreg tests passed. Also, the
Checker Framework doesn't rely on Types and therefore also continued
to pass.

However, removing cloning was not correct: Type.typeAnnotations is set in
com.sun.tools.javac.code.TypeAnnotations.TypeAnnotationPositions.typeWithAnnotations(JCTree,
Type, List<TypeCompound>)
once the ambiguity between declaration and type annotations has been resolved.
At that point, Type instances are being shared and setting field
Type.typeAnnotations modifies all instances, showing the effect
Bhavesh noticed.

The simplest and ugliest solution would be to add cloning again.

I tried working on a nicer solution: introduce a class
javac.code.Type.AnnotatedType that behaves like its underlying type
and also manages a list of type annotations.
I also added javax.lang.model.type.AnnotatedType.
After fixing a few problems, this mostly works again. However, I still
need a way to create a duplicate of an existing Type in
typeWithAnnotations, in order to replace a Type with an AnnotatedType.
The complication is that the AnnotatedType can be an enclosing type
for another type and we therefore need to duplicate the whole Type.

Is there a simple way to create a duplicate of an arbitrary
javac.code.Type instance?
I looked at the existing Type.Mapping and Type.Visitor subclasses, but
didn't find something suitable.

Which approach would you prefer, re-introducing cloning of Type or
spending more time on introducing AnnotatedType and a clean copy
mechanism?

Joel, did you already start to work on javax.lang.model? Will we
expose an AnnotatedType there?

All comments welcome,
cu, WMD.

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