diff --git a/stdlib/public/core/StringGuts.swift b/stdlib/public/core/StringGuts.swift
index 5a277536ca7..6e156030c62 100644
--- a/stdlib/public/core/StringGuts.swift
+++ b/stdlib/public/core/StringGuts.swift
@@ -637,10 +637,9 @@ extension _StringGuts {
     return _copyToNativeStorage(of: CodeUnit.self, from: 0..<count)
   }
 
+  @inlinable
   @_specialize(where CodeUnit == UInt8)
   @_specialize(where CodeUnit == UInt16)
-  @_specialize(where CodeUnit == UTF16.CodeUnit)
-  @inlinable
   internal
   func _copyToNativeStorage<CodeUnit>(
     of codeUnit: CodeUnit.Type = CodeUnit.self,
diff --git a/stdlib/public/core/StringStorage.swift b/stdlib/public/core/StringStorage.swift
index f6a0217609c..36011e948c5 100644
--- a/stdlib/public/core/StringStorage.swift
+++ b/stdlib/public/core/StringStorage.swift
@@ -52,8 +52,10 @@ final class _SwiftStringStorage<CodeUnit>
 where CodeUnit : UnsignedInteger & FixedWidthInteger {
 
   /// Create uninitialized storage of at least the specified capacity.
-  @inlinable
+  @usableFromInline
   @nonobjc
+  @_specialize(where CodeUnit == UInt8)
+  @_specialize(where CodeUnit == UInt16)
   internal static func create(
     capacity: Int,
     count: Int = 0
@@ -191,7 +193,7 @@ extension _SwiftStringStorage {
 extension _SwiftStringStorage {
   // Append operations
 
-  @inlinable
+  @inlinable // TODO(inlinability): @usableFromInline - P3
   @nonobjc
   internal final func _appendInPlace<OtherCodeUnit>(
     _ other: _UnmanagedString<OtherCodeUnit>
@@ -203,7 +205,7 @@ extension _SwiftStringStorage {
     self.count += otherCount
   }
 
-  @inlinable
+  @inlinable // TODO(inlinability): @usableFromInline - P3
   @nonobjc
   internal final func _appendInPlace(_ other: _UnmanagedOpaqueString) {
     let otherCount = Int(other.count)
@@ -212,7 +214,7 @@ extension _SwiftStringStorage {
     self.count += otherCount
   }
 
-  @inlinable
+  @inlinable // TODO(inlinability): @usableFromInline - P3
   @nonobjc
   internal final func _appendInPlace<C: Collection>(contentsOf other: C)
   where C.Element == CodeUnit {
@@ -225,7 +227,7 @@ extension _SwiftStringStorage {
     count += otherCount
   }
 
-  @inlinable
+  @inlinable // TODO(inlinability): @usableFromInline - P3
   @_specialize(where C == Character._SmallUTF16, CodeUnit == UInt8)
   @nonobjc
   internal final func _appendInPlaceUTF16<C: Collection>(contentsOf other: C)