confused about pure functions

[markusle]

Using dmd 2.058 I can compile the following

pure bool has_path(string paths[], string needle) {

    paths[0] = "bad";

    ... do something else ...

    return false;
}

and change the passed in array "paths". Isn't this a violation of
has_path's pure contract? Shouldn't all pure function parameters
be passed as "in" to avoid side effects. Sorry if I missed
something obvious.