Nice to @Share?

[Neal Gafter]

On Tue, Feb 23, 2010 at 1:22 AM, Alex Buckley <Alex.Buckley at sun.com> wrote:
> As Neal said, @Shared is mentioned in non-normative text lifted directly
> from John Rose's mail. I have never thought it appropriate for an
> annotation to turn a local variable into a shared variable. That is,
> once a method-scoped variable is morally "shared", it isn't a local
> variable (stack-allocated, single-thread-visibility, no volatility) at
> all. It's an eighth kind of variable in JLS 4.12.3. (And being 'final'
> is orthogonal.) A restricted keyword - suggestions welcome - is more
> than appropriate.

The definition of "local variable" in (§4.12.3) is "Local variables
are declared by local variable declaration statements (§14.4).
Whenever the flow of control enters a block (§14.2)  or for statement
(§14.14), a new variable is created for each local variable declared
in a local variable declaration statement immediately contained within
that block or for statement. A local variable declaration statement
may contain an expression which initializes the variable. The local
variable with an initializing expression is not initialized, however,
until the local variable declaration statement that declares it is
executed. (The rules of definite assignment (§16) prevent the value of
a local variable from being used before it has been initialized or
otherwise assigned a value.) The local variable effectively ceases to
exist when the execution of the block or for statement is complete."

The only part of that requiring rewording in the presence of lambdas
that can access local variables from the enclosing scope is the last
sentence.  The rewording is required whether or not such variables are
final.  In fact, that last sentence appears to conflict with the fact
that final variables can be accessed in an anonymous inner class after
the scope containing the variable has completed.

A new keyword, while better than what programmers have to do today, is
still boilerplate.