// which may be retained and mutated even after WriteHeader.
	// handlerHeader is copied into cw.header at WriteHeader
	// time, and privately mutated thereafter.
	handlerHeader Header
	calledHeader  bool // handler accessed handlerHeader via Header

	written       int64 // number of bytes written in body
	contentLength int64 // explicitly-declared Content-Length; or -1

			}

			if tc.expectedReader != nil {
				if mw.CalledReader == nil {
					t.Fatal("did not call ReadFrom")
				}

				var actualReader reflect.Type
				lr, ok := mw.CalledReader.(*io.LimitedReader)
				if ok && tc.limitedReader {
					actualReader = reflect.TypeOf(lr.R)
				} else {
					actualReader = reflect.TypeOf(mw.CalledReader)
					// We have to handle this special case for genericWriteTo in os,