First pass:
- Eliminate rules with unresolved name symbols in LHS
- Eliminate simplified non-conformance rules
Second pass:
- Eliminate non-minimal conformance rules
Third pass:
- Eliminate all other non-conformance rules
If you have a concrete requirement with a non-canonical substitution, like
A : P, A == G<B.T>
We add an induced rule for the abstract type witness,
A.T == B.T
This rule has a rewrite path in terms of the previous two rules, but we
want to try to eliminate the other two rules first.
This new ordering ensures we eliminate the simplified rule A == G<B.T> and
compute minimal conformances before we get around to considering A.T == B.T,
which can no longer be eliminated by that point.
If we eliminate A.T == B.T first, we end up with simplified concrete
type and concrete conformance rules which cannot be eliminated:
A.[concrete: G<B.T>] => A
A.[concrete: G<B.T> : P] => A
This changes the minimized signature in an incompatible way in two test cases.
In Generics/rdar83308672.swift, the signature becomes equivalent to what the
GSB used to output.
In Generics/sr10532.swift, the GSB would output an invalid signature anyway,
so it doesn't matter.
Instead of finding the best redundancy candidate from the first
homotopy generator that has one, find the best redundancy
candidate from *all* homotopy generators that have one.
This correctly minimizes the "Joe Groff monoid" without hitting
the assertion guarding against simplified rules being non-redundant.
It also brings us closer to being able to correctly minimize
the protocol from https://bugs.swift.org/browse/SR-7353.
