On Mon, 16 Nov 2020 13:30:06 GMT, Vicente Romero <vrom...@openjdk.org> wrote:
> Please review the code for the second iteration of sealed classes. In this > iteration we are: > > - Enhancing narrowing reference conversion to allow for stricter checking of > cast conversions with respect to sealed type hierarchies > - Also local classes are not considered when determining implicitly declared > permitted direct subclasses of a sealed class or sealed interface > - renaming Class::permittedSubclasses to Class::getPermittedSubclasses, still > in the same method, the return type has been changed to Class<?>[] instead of > the previous ClassDesc[] > - adding code to make sure that annotations can't be sealed > - improving some tests > > TIA > > Related specs: > [Sealed Classes > JSL](http://cr.openjdk.java.net/~gbierman/jep397/jep397-20201104/specs/sealed-classes-jls.html) > [Sealed Classes > JVMS](http://cr.openjdk.java.net/~gbierman/jep397/jep397-20201104/specs/sealed-classes-jvms.html) > [Additional: Contextual > Keywords](http://cr.openjdk.java.net/~gbierman/jep397/jep397-20201104/specs/contextual-keywords-jls.html) I left some comments re. the changes in cast conversion routine src/jdk.compiler/share/classes/com/sun/tools/javac/code/Types.java line 1659: > 1657: result = isCastable.visit(t,s); > 1658: } > 1659: if ((t.tsym.isSealed() || s.tsym.isSealed())) { It would probably be better to only run this extra check if `result == true`, to minimize compatibility impact. src/jdk.compiler/share/classes/com/sun/tools/javac/code/Types.java line 1672: > 1670: } > 1671: // if both are classes or both are interfaces, shortcut > 1672: if (ts.isInterface() == ss.isInterface()) { What happens with code like this? interface A permits B { } non-sealed interface B extends A { } interface C { } class D implements C, B { } // this is a valid witness for both A and C, but A and C are unrelated with subtyping class Test { void m(A a, C c) { a = (A)c; } }``` Note that, w/o sealed types, the above snippet compiles ok - e.g. casting C to A is not going to give problems (as there could be a common subtype D <: A, C). ------------- PR: https://git.openjdk.java.net/jdk/pull/1227
