We used to skip a pass if any of the three flags were set, but we have
to check them separately to ensure that all flags are independently
set correctly.
We have three simplification passes, give each one its own predicate:
- Left hand side simplification
- Right hand side simplification
- Substitution simplification
This is for debugging output and will also allow me to tighten up
some invariants.
If a type parameter is subject to both a conformance requirement
and a concrete type requirement, the concrete type might conform
conditionally.
In this case, introduce new requirements to satisfy the conditional
conformance.
Since this can add new hitherto-unseen protocols to the rewrite
system, restrict this feature to top-level generic signatures, and
not protocol requirement signatures. Allowing this to occur in
protocol requirement signatures would change the connectivity of
the protocol dependency graph (and hence the connected components)
during completion, which would be a major complication in the
design. The GSB already enforces this restriction.
I changed the existing conditional_requirement_inference.swift test
to run with -requirement-machine-inferred-signatures=verify. Since
one of the test cases there triggers an unrelated bug in the
Requirement Machine, I split it off into a new file named
conditional_requirement_inference_2.swift which still runs with
the GSB. Once the bug is fixed I'll merge the files again.
A type parameter subject to an AnyObject requirement might also be subject
to a concrete type requirement. There are two cases to handle here:
- If the concrete type is a class, the layout requirement is redundant.
- If the concrete type is not a class, we have a conflict.
There is an existing test that's good enough; I just changed it to
run with -requirement-machine-inferred-signatures=verify.
It doesn't actually do this yet, but the idea is to look at the
total rule count before and after, instead of just looking at the
induced rules array (which I will delete in the next commit).
Conditional requirement inference needs to be able to add rewrite rules
from the requirement signatures of hitherto-unseen protocols, so to
help with that, extract out the RuleBuilder's ProtocolMap and move it
into the RewriteSystem.
We can end up with two redundant concrete type rules on the same
term, but we would crash in homotopy reduction because the rules
were incomparable due to the concrete type symbol at the end.
If one of them is conflicting though, we don't really care about
the homotopy reduction order, so skip the check if the other
rule was already marked conflicting.
