[JSR308] array-valued annotations
Joe.Darcy at Sun.COM
Sun Jan 28 16:17:46 EST 2007
I joined the mailing list recently; previously I was the spec lead for
JSR 269, which added a standardized annotation processing API to JDK 6.
Michael Ernst wrote:
>> a multidimensional array has to contain all the same type,
>> regardless of the number of dimensions.
> I agree that the type at the "leaves" must all be the same -- and they
> must all have the same annotation.
> However, Java does support different types at different levels of an
> array. For instance, consider an array of type Document.
> * The first level of the array has type Document.
> * The next level (i.the first level's elements) has type Document.
> * The final level (the leaves) has type Document.
> These are distinct types, though Java enforces that they have a
> specific relationship to one another.
At runtime these specific constraints are enforced via a store check
that relies on reified information about the array's type. I believe
adding similar reification of annotation information would be
problematic and at compile time only accepting programs that didn't need
such runtime checks would be too incompatible.
joe.darcy at sun.com
> It seems useful to permit different annotations on the distinct types
> at each level. However, the types/annotations at different levels
> should have specific relationships to one another, just as array types
> already do. The syntax can enforce this, just as that for array types
> already does. For instance, you correctly note that the type
> "Document[Object]" makes no sense; and the Java syntax makes it
> impossible to write such a nonsensical type.
> -Michael Ernst
> mernst at csail.mit.edu
> JSR308 mailing list
> JSR308 at lists.csail.mit.edu
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