Bad diagnostic about memberwise `init` not being public

Description

No response

Reproduction

public struct Number: RawRepresentable {
  public let rawValue: Int
}

398 | public struct Number: RawRepresentable {
    |               `- error: initializer 'init(rawValue:)' must be declared public because it matches a requirement in public protocol 'RawRepresentable' [witness_not_accessible_proto]
399 |   public let rawValue: Int
400 | }

Expected behavior

This diagnostic is not great:

1. What initializer? (The implicit memberwise initializer).
2. How do I or can I at all declare it public? (An implicit memberwise initializer cannot be public).
3. What should I do to make this work? (Declare an explicit initializer + fix-it).

Environment

Swift version 6.2-dev (LLVM 1a588e5b044c46f, Swift 55189bae8e55169)

Additional information

No response