split - String splitting in the D language -

i learning d , trying split strings:

   import std.stdio;    import std.string;      auto file = file(path, "r");      foreach (line; file.byline) {            string[] parts = split(line); 

this fails compile with:

error: cannot implicitly convert expression (split(line)) of type char[][] string[] 

this works:

    auto file = file(path, "r");      foreach (line; file.byline) {            char[][] parts = split(line); 

but why have use char[][]? far understand documentation, says split returns string[], prefer.

use split(line.idup);

split template function, return type depends on argument. file.byline.front returns char[] reused performance reasons. if need parts after current loop iteration have dup or idup, whatever need.