Use "default" keyword for default visibility.

[Jeremy Manson]

Could you dig up the example?  It is hard to see why this is
compelling without it.

I think it would have to be a warning instead of an error, because
otherwise, it is a change that breaks backwards compatibility (i.e.,
it makes old stuff not compile).  I think there is a reasonable sized
danger in introducing so many warnings for a change this small; people
are likely to ignore / get upset about the flood of warnings that
their compiler is suddenly generating.

Did you consider the use of annotations as an alternative?  In code
that I write, if something has package-private visibility, it is
usually for testing; Google has a @VisibleForTesting annotation that
we use.

Also, why not use the package keyword?

Jeremy

On Sun, Mar 1, 2009 at 1:01 AM, Adrian Kuhn <akuhn at iam.unibe.ch> wrote:
> PROJECT COIN SMALL LANGUAGE CHANGE PROPOSAL FORM v1.0
>
> AUTHOR(S): Adrian Kuhn
>
> OVERVIEW
>
> Allow the "default" keyword to be used as modifier for default
> visibility. In strict mode, missing use of default is a warning /
> error, in compatibility mode both the current (ie no default keyword)
> and the new syntax are accepted.
>
> FEATURE SUMMARY: Use "default" keyword for default visibility.
>
> MAJOR ADVANTAGE: The missing keyword for default visibility breaks the
> symmetry of visibility modifiers. Since it is the only implicit
> modifier, omitting any of the three explicit modifiers by mistake may
> be the source of unexpected behavior and thus hard to track down bugs.
> (There was an example on a blog post recently, but I cannot find it
> know).
>
> MAJOR BENEFIT: Symmetry of visibility modifiers is restored.
>
> MAJOR DISADVANTAGE: Two ways to express the same thing (in
> compatibility mode).
>
> ALTERNATIVES: Using a comment such as /* default */ is not an
> alternative since such comments are not processed by the compiler.
>
> EXAMPLES
>
> public class C {
>        default Field f;
> }
>
> SIMPLE EXAMPLE: See above.
>
> ADVANCED EXAMPLE: None.
>
> DETAILS
>
> SPECIFICATION: "default" is already a keyword and introducing it as a
> new visibility modifier is save, it does not lead to ambiguous grammar.
>
> COMPILATION: Same as now for implicit default visibility.
>
> TESTING: Same as now for implicit default visibility.
>
> LIBRARY SUPPORT: None.
>
> REFLECTIVE APIS: None.
>
> OTHER CHANGES: None.
>
> MIGRATION: Compatibility mode allows both, implicit and explicit
> default visibility, to be used at  the same time.
>
> COMPATIBILITY
>
> BREAKING CHANGES: None.
>
> EXISTING PROGRAMS: Work fine in compatibility mode.
>
> REFERENCES
>
> EXISTING BUGS: To my best knowledge, none.
>
> URL FOR PROTOTYPE (optional):
>
>
>
>