[stdlib] Mark two types @usableFromInline; they satisfy requirements (#18862)

jrose-apple · web-flow · commit 9f7d6cea681a · 2018-08-21T09:40:56.000-07:00
Otherwise, the textual interface won't see them, and any inlinable
code that wants to make use of the protocol might get confused.
We should have a check for this in the compiler itself, but for now
I'm just providing this change to get unblocked.
diff --git a/stdlib/public/core/UnmanagedOpaqueString.swift b/stdlib/public/core/UnmanagedOpaqueString.swift
@@ -223,8 +223,8 @@ extension _UnmanagedOpaqueString : RandomAccessCollection {
 }
 
 extension _UnmanagedOpaqueString : _StringVariant {
-  internal typealias Encoding = Unicode.UTF16
-  internal typealias CodeUnit = Encoding.CodeUnit
+  @usableFromInline internal typealias Encoding = Unicode.UTF16
+  @usableFromInline internal typealias CodeUnit = Encoding.CodeUnit
 
   @inlinable
   var isASCII: Bool {

Original file line number	Diff line number	Diff line change
`@@ -223,8 +223,8 @@ extension _UnmanagedOpaqueString : RandomAccessCollection {`
`223`	`223`	`}`
`224`	`224`
`225`	`225`	`extension _UnmanagedOpaqueString : _StringVariant {`
`226`		`- internal typealias Encoding = Unicode.UTF16`
`227`		`- internal typealias CodeUnit = Encoding.CodeUnit`
	`226`	`+ @usableFromInline internal typealias Encoding = Unicode.UTF16`
	`227`	`+ @usableFromInline internal typealias CodeUnit = Encoding.CodeUnit`
`228`	`228`
`229`	`229`	`@inlinable`
`230`	`230`	`var isASCII: Bool {`