- Don't pass 'verify' since it's now the default
- Update tests where diagnostics changed in a correct way to pass 'on' instead
- Delete compiler_scale/explicit_requirements_perf.swift since it's not testing anything with the requirement machine
Associated type redeclarations occasionally occur to push around
associated type witness inference. Suppress the warning about redeclarations
that add no requirements (i.e., have neither an inheritance nor a
where clause).
Introduce a warning about redeclaring the associated types from an
inherited protocol in the protocol being checked:
* If the new declaration is an associated type, note that the
declaration could be replaced by requirements in the protocol's
where clause.
* If the new declaration is a typealias, note that it could be
replaced by a same-type constraint in the protocol's where clause.
Move the storage for the protocols to which a particular potential
archetype conforms into EquivalenceClass, so that it is more easily
shared. More importantly, keep track of *all* of the constraint
sources that produced a particular conformance requirement, so we can
revisit them later, which provides a number of improvements:
* We can drop self-derived requirements at the end, once we've
established all of the equivalence classes
* We diagnose redundant conformance requirements, e.g., "T: Sequence"
is redundant if "T: Collection" is already specified.
* We can choose the best path when forming the conformance access
path.
When two associated types with the same name are on the same dependent
type T, introduce a same-type constraint between the the corresponding
potential archetypes. This eliminates ordering dependencies in the
archetype builder.
Fixes the reduced test case from rdar://problem/23149063, but doesn't
fully address the idea that we should be tracking associated type
redeclarations in a meaningful way.
