Robert Widmann 01d272073a Requestify Witness Resolution ...

Witness matching is a source of a lot of ad-hoc cycles, and mixes the
logic that performs resolution, caching, validation, and cycle detection into one
place.  To make matters worse, some checkers kick off other checks in
order to cache work for further declarations, and access an internal
cache on their subject conformance for many requirements at once, or
sometimes just one requirement.

None of this fits into the request evaluator's central view of the
caching.  This is further evidenced by the fact that if you attempt to
move the caching step into the evaluator, it overcaches the same
witness and trips asserts.

As a start, define requests for the resolution steps, and flush some
hacks around forcing witness resolution. The caching logic is mostly
untouched (the requests don't actually cache anything), but some cycle
breaking is now handled in the evaluator itself.  Once witness matching
has been refactored to cache with the evaluator, all of these hacks can
go away.

My urge to destroy the LazyResolver outweighs the compromises here.

2019-11-05 13:28:07 -08:00

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