ScopedValue.runWhere not returning scope

[Andrew Haley]

On 6/10/24 17:25, Robert Engels wrote:
> I think the question is more - what are the threads doing with this
> object between the open and close. This is what controls whether or not
> the object can be immutable - which from my reading is the general
> design/limitation of a scoped variable.

Exactly. So something (what?) returns a Scope object. But that can't change
the current scoped value context.

Here's a fundamental property of a scoped value:

   The result of aScopedValue.get() does not ever change within the execution
   context of a method. Sure, its value might get overridden in the context of a
   callee, but when that callee returns the scoped value has its original
   value.

   So, in this code

   final ScopedValue aScopedValue = ...;
   final var x = aScopedValue.get();
   // Any Java code at all...
   final var y = aScopedValue.get();

   assert(x == y); // Always succeeds

That is to say, you can read a scoped value, put it in a local, and use
that local, and it is a hard guarantee that will have exactly the same
effect as repeatedly calling aScopedValue.get() .

-- 
Andrew Haley  (he/him)
Java Platform Lead Engineer
Red Hat UK Ltd. <https://www.redhat.com>
https://keybase.io/andrewhaley
EAC8 43EB D3EF DB98 CC77 2FAD A5CD 6035 332F A671