Swift 6 typed-throws unable to detect exhaustive catch statements

[NachoSoto]

Description

Consider the example below. Both Error.a and Error.b are caught, but the compiler is unable to infer that.

Reproduction

enum Error: Swift.Error {
  case a
  case b
}

func f() throws(Error) {
  throw .a
}

func g() {
  do {
    // Errors thrown from here are not handled because the enclosing catch is not exhaustive
    try f()
  } catch .a {
  } catch .b {
  }
}

Expected behavior

Code compiles

Environment

swift-driver version: 1.109.2 Apple Swift version 6.0 (swiftlang-6.0.0.3.300 clang-1600.0.20.10)
Target: arm64-apple-macosx14.0

Additional information

No response