clnt.File superficially implements io.Writer

[aarzilli]

io.Writer says that Write must return a non-nil error if it returns n < len(p) but clnt.(*File).Write can return n < len(buf) and nil as an error.

The effect is that using a clnt.File with something that takes an io.Writer, like io.Copy, will compile and appear to work correctly until a large write (>4kb?) is attempted, and then break.

[aarzilli]

IMHO Write should either be made conform with io.Writer, removed entirely, or the documentation should have a big warning about using Files as io.Writers.