Typechecking crashes when enum contains a duplicated string raw value

[tayloraswift]

struct A
{
    enum CodingKeys:String
    {
        case a
        case b
        case b
    }
}

crashes with

sourcekit-lsp: /home/build-user/swift/lib/Sema/TypeCheckDecl.cpp:1340: evaluator::SideEffect swift::EnumRawValuesRequest::evaluate(swift::Evaluator &, swift::EnumDecl *, swift::TypeResolutionStage) const: Assertion `lastExplicitValueElt && "should not be able to have non-unique raw values when " "relying on autoincrement"' failed.
PLEASE submit a bug report to https://github.com/llvm/llvm-project/issues/ and include the crash backtrace.
Stack dump:
0.	While evaluating request TypeCheckSourceFileRequest(source_file "/swift/swift-mongodb/crash.0.swift")
1.	While type-checking 'A' (at /swift/swift-mongodb/crash.0.swift:1:1)
2.	While type-checking 'CodingKeys' (at /swift/swift-mongodb/crash.0.swift:3:5)
3.	While type-checking 'a' (at /swift/swift-mongodb/crash.0.swift:5:14)
4.	While evaluating request EnumRawValuesRequest(main.(file).A.CodingKeys@/swift/swift-mongodb/crash.0.swift:3:10, interface)
[Error - 3:14:02 AM] Request textDocument/codeAction failed.

on swift-5.8-DEVELOPMENT-SNAPSHOT-2023-02-09-a . (amazon linux2 nightly docker container)

[ahoppen]

rdar://105761206

[ahoppen]

Reduced example. The following files to type check on current main. Sending over to apple/swift because this is not a SourceKit-LSP specific issue.

enum MyEnum: String {
  case b
  case b
}