[e-lang] Proposal: Remove parameters from __whenMoreResolved/__whenBroken reactors

[Mark S. Miller]

Kevin Reid wrote:
> I haven't noticed an explanation being posted, and I have not  stumbled 
> across the reason myself. Could you write it or point to  where it was 
> posted?

The DelayedRedirector and the Redirector use the reactor argument to propagate 
promise resolution from the head of a remote reference to the tail. This same 
mechanism is used to propagate partial resolution, shortening multivat promise 
chains.

For example, let's say Xb is a remote promise in VatB for a local promise Xa 
whose promise/resolver pair is on VatA, and Ya is a remote promise in VatA for 
a local promise Yc on VatC. If VatA resolves Xa to Ya, this notifies the 
DelayedRedirector for Xb with a new Yb as the argument. (This Yb is made by 
during unserialization of the reactor notification message.) The 
DelayedRedirector uses this argument to shorten Xb to be equivalent to Yb, 
cutting VatA out of the promise chain. If nothing else is retaining the 
portion of this promise chain in VatA, it can will be gc'ed.

When I tried to simplify the __whenMoreResolved protocol to remove the reactor 
argument, I found I had no other means to shorten promise chains, or even to 
resolve a remote promise when its target promise resolved.

-- 
Text by me above is hereby placed in the public domain

     Cheers,
     --MarkM