test/Sema/diag_express_tuple.swift

// RUN: %target-typecheck-verify-swift

func foo(a : [(some: Int, (key: Int, value: String))]) -> String {
  for (i , (j, k)) in a { // expected-error {{cannot express tuple conversion '(some: Int, (key: Int, value: String))' to '(Int, (Int, String))'}}{8-8=some: }} {{13-13=key: }} {{16-16=value: }}
    if i == j { return k }
  }
}

func rdar28207648() -> [(Int, CustomStringConvertible)] {
  let v : [(Int, Int)] = []
  return v as [(Int, CustomStringConvertible)] // expected-error {{cannot express tuple conversion '(Int, Int)' to '(Int, CustomStringConvertible)'}}
}

class rdar28207648Base {}
class rdar28207648Derived : rdar28207648Base {}

func rdar28207648(x: (Int, rdar28207648Derived)) -> (Int, rdar28207648Base) {
  return x as (Int, rdar28207648Base) // expected-error {{cannot express tuple conversion '(Int, rdar28207648Derived)' to '(Int, rdar28207648Base)'}}
}