Add typecheck tests for @yield_once / @yields

test/Parse/coroutines.swift

@@ -0,0 +1,41 @@
+// RUN: %target-typecheck-verify-swift
+
+@yield_once func coro(_ x : inout Float) -> inout @yields Float {
+  var _x = Float(0.0)
+  yield &_x
+  x = Float(_x)
+}
+
+func retCoro() -> @yield_once (_ x : inout Float) -> inout @yields Float {
+  return coro
+}
+
+@yield_once func coroWithResult(_ x : Float) -> (yield: inout @yields Float, result: Float) {
+  var _x = Float(0.0)
+  yield &_x
+  return _x
+}
+
+func retCoroWithResult() -> @yield_once (_ x : Float) -> (inout @yields Float, Float) {
+  return coroWithResult
+}
+
+@yield_once func coroGen<T>(_ x : inout T) -> inout @yields T {
+  var _x = x
+  yield &_x
+  x = _x
+}
+
+func retGenCoro<T>() -> @yield_once (_ x : inout T) -> inout @yields T {
+  return coroGen
+}
+
+@yield_once func coroGenWithResult<T>(_ x : T) -> (yield: inout @yields T, result: T) {
+  var _x = x
+  yield &_x
+  return _x
+}
+
+func retCoroGenWithResult<T>() -> @yield_once (_ x : T) -> (inout @yields T, T) {
+  return coroGenWithResult
+}