[Sema] Fix a crash when attempting to synthesise raw representable conformance

[theblixguy]

This PR fixes a crash when attempting to derive raw representable conformance for an enum which has cases with payloads.

enum Crash: String {
  case foo
  case bar(String)
    
  static let shared = Crash()
}

extension Crash {
  init() { self = .foo }
}

Resolves SR-10108.

[theblixguy]

cc @jrose-apple @xedin @slavapestov

[jrose-apple]

Thanks, Suyash! Do we still produce the usual diagnostic about mixing raw values and associated types?

[jrose-apple]

@swift-ci Please test

[theblixguy]

Yeah, we do: enum with raw type cannot have cases with arguments

[swift-ci]

Build failed
Swift Test Linux Platform
Git Sha - 4eebc8e

[swift-ci]

Build failed
Swift Test OS X Platform
Git Sha - 4eebc8e

[theblixguy]

Unrelated build failure: 12:09:32 /Users/buildnode/jenkins/workspace/swift-PR-osx/branch-master/swift/lib/ClangImporter/ClangImporter.cpp:769:23: error: no matching constructor for initialization of 'clang::Preprocessor'

[jrose-apple]

Must have caught it between Duncan's Clang and Swift patches.

@swift-ci Please test

[swift-ci]

Build failed
Swift Test OS X Platform
Git Sha - 4eebc8e

[jrose-apple]

…right, it's not just the merge into Clang; it has to propagate from 5.1 to stable.

[swift-ci]

Build failed
Swift Test Linux Platform
Git Sha - 4eebc8e

[theblixguy]

@jrose-apple The changes got reverted, so it should be fine now. Could you trigger the CI again? Thanks!

[jrose-apple]

@swift-ci Please test

[swift-ci]

Build failed
Swift Test Linux Platform
Git Sha - 4eebc8e

[theblixguy]

Oops, I forgot to prefix the RUN args with not 😅 @jrose-apple Can you trigger the CI one more time? Sorry!

[swift-ci]

Build failed
Swift Test OS X Platform
Git Sha - 4eebc8e

[jrose-apple]

@swift-ci Please test

[jrose-apple]

…

@swift-ci Please test macOS

[jrose-apple]

This one's probably good to cherry-pick too!

[theblixguy]

@jrose-apple Done - #23428 😄