RFR: 8343540: Report preview error for inherited effectively-preview methods

[Alex Buckley]

On 11/7/2024 7:44 AM, Jan Lahoda wrote:
> The proposal herein is that invoking a method on a receiver that is
> not of preview type itself, but the method is declared in a preview
> class or interface, the method will be considered to be a preview
> method, and the appropriate error or warning will be printed.
> Similar behavior is implementing for dereferencing fields.

> The proposal herein is to produce an error or warning for method
> declared inside a non-preview class or interface, which is
> overridden by a method declared inside a preview class or interface.
Thank you Jan, these are important improvements to javac's handling of 
preview APIs.

For the second proposal above, I think you mean "... which ~is 
overridden by~ +overrides+ a method declared inside a preview class or 
interface."

javac will give a warning/error where the non-preview class Test1 
declares the test method, because Test1 overrides the test method 
declared in the preview interface NewAPI.


I would add that the JDK class ExistingRetrofittedClass, which 
implements NewAPI, can override the test method without a warning/error. 
This is because ExistingRetrofittedClass is "participating" in the 
preview API.


Suppose ExistingRetrofittedClass does indeed override the test method. I 
would expect both of the examples in your original mail to give a 
warning/error. Both the invocation of `c.test()`, and the overriding of 
test in Test1, refer to an "effectively" preview method.

Alex