* Obsolete ModifierSlice typealiases in 5.0
* Obsolete *Indexable in 5.0
* Obsolete IteratorOverOne/EmptyIterator in 5.0
* Obsolete lazy typealiases in 5.0
* Drop .characters from tests
* Obsolete old literal protocols in 5.0
* Obsolete Range conversion helpers in 5.0
* Obsolete IndexDistance helpers in 5.0
* Obsolete Unsafe compat helpers in 5.0
* Obsolete flatMap compatibility helper in 5.0
* Obsolete withMutableCharacters in 5.0
* Obsolete customPlaygroundQuickLook in 5.0
* Deprecate Zip2Sequence streams in 5.0
* Replace * with swift on lotsa stuff
* Back off obsoleting playground conformances for now
The various _*Indexable protocols only exist to work around the lack of
recursive protocol constraints. Eliminate all of the *_Indexable protocols,
collapsing their requirements into the corresponding Collection protocol
(e.g., _MutableIndexable —> Collection).
This introduces a number of extraneous requirements into the various
Collection protocols to work around bugs in associated type
inference. Specifically, to work around the lack of "global" inference
of associated type witnesses. These hacks were implicitly present in
the *Indexable protocols; I've made marked them as ABI FIXMEs here so
we can remove them when associated type inference improves.
Fixes rdar://problem/21935030 and a number of ABI FIXMEs in the library.
Reimplement isSelfDerivedSource() in terms of the new
visitPotentialArchetypesAlongPath(). Aside from being clearer and
shorter, this formulation eliminates some hackery (the direct
"NestedType" lookup) that was mostly masking a bug in
updateNestedTypeForConformance() where we created a
nested-type-name-match source with an incorrect source for the
purposes of concretizing the nested type.
Fixes SR-4458 / rdar://problem/31375569.
