Failed to produce diagnostic for expression

[AnthonyLatsis]

Description

No response

Reproduction

struct Mootex<T> {
  func withLock<Result>(_: (T) -> Result) -> Result {}
}

func never() -> Never {}

struct Test {
  let _i = Mootex<Int>()

  var i: Int {
    _i.withLock { _ in
      never()
    }
  }
}

Expected behavior

No error.

Environment

Swift version 6.3-dev (09c828c)

Additional information

No response

[AnthonyLatsis]

Added a test in #85588.

[jamieQ]

notes: adding an explicit return before the _i.withLock ... expression seems to resolve the ambiguity. also appears it used to typecheck successfully a while ago (swift 5.0 and earlier): https://swift.godbolt.org/z/jK3Pscodf.