swiftlang#37992 introduced a warning when you
were likely to confuse `self` with `TypeName.self`, this also applied to
enum cases that were named `self`, these cases should not be easily
confused at call sites since their use requires prefixing them with a
`.`. There was also no way to avoid this warning since other syntax such
as `TypeName.self`, which produces the enum type instead, or
`` TypeName.`self` `` which produced the same warning again.
Fixes https://bugs.swift.org/browse/SR-15691
(cherry picked from commit f6b2e2e)

because they need a minimum deployment target, which might not be available in client modules, which de-serialize such functions.

... functions.

...for-enum-cases-named-self-41520
[5.6] Fix invalid warning for enum cases named self

...ecks-5.6
Cherry-pick fixes for availability-checks.