name: "fill error, discard less",
			r: newScriptedReader(func(p []byte) (n int, err error) {
				if len(p) < 5 {
					panic("unexpected small read")
				}
				return 5, errors.New("5-then-error")
			}),
			n:            4,
			want:         4,
			wantErr:      nil,
			wantBuffered: 1,
		},
		{
			name: "fill error, discard equal",
			r: newScriptedReader(func(p []byte) (n int, err error) {