As opposed to a generic TextOutputStream value.
Tried to add this unit test:
```swift
func testWriteTo() {
let (writer1,reader1) = streams()
var (writer2,reader2) = streams()
writer1.write("something")
writer1.close()
writer2.write("h")
reader1.write(to: &writer2)
XCTAssertEqual(reader2.read(), "something")
}
but the first `writer2.write` causes an EXC_BAD_ACCESS exception here:
```swift
extension WritableStream {
public func write(_ x: String) {
filehandle.write(x, encoding: encoding)
}
```
No idea why.
Kare Morstol
f195472d87