func testAsyncSequence<Seq: AsyncSequence>(_ seq: Seq) async throws where Seq.Element == Int {
    async let result: Int = seq.reduce(0) { $0 + $1 }
}
tmp.swift:2:15: warning: immutable value 'result' was never used; consider replacing with '_' or removing it
    async let result: Int = seq.reduce(0) { $0 + $1 }
              ^~~~~~
              _
tmp.swift:2:29: error: call can throw, but it is executed in a non-throwing autoclosure
    async let result: Int = seq.reduce(0) { $0 + $1 }
                            ^
tmp.swift:2:29: note: call is to 'rethrows' function, but a conformance has a throwing witness
    async let result: Int = seq.reduce(0) { $0 + $1 }
                            ^

func testAsyncSequence<Seq: AsyncSequence>(_ seq: Seq) async throws where Seq.Element == Int {
    async let _: Int = seq.reduce(0) { $0 + $1 }
}
tmp.swift:2:24: error: call can throw but is not marked with 'try'
    async let _: Int = seq.reduce(0) { $0 + $1 }
                       ^~~~~~~~~~~~~~~~~~~~~~~~~
tmp.swift:2:24: note: call is to 'rethrows' function, but a conformance has a throwing witness
    async let _: Int = seq.reduce(0) { $0 + $1 }
                       ^
tmp.swift:2:24: error: expression is 'async' but is not marked with 'await'
    async let _: Int = seq.reduce(0) { $0 + $1 }
                       ^~~~~~~~~~~~~~~~~~~~~~~~~
                       await
tmp.swift:2:24: note: call is 'async'
    async let _: Int = seq.reduce(0) { $0 + $1 }
                       ^

func f() async throws -> Int { 3 }
func g() async {
    async let x: Int = f()
}