char[] to string

[Jonathan Sternberg]

Why doesn't this work?

import std.stdio;

string copy_string(char [] input)
{
    return input.dup;
}

int main()
{
    char [] buf = ['h', 'e', 'l', 'l', 'o'];
    writeln( copy_string(buf) );
}

I want to do something more complex. In my code, I want to have a dynamic
array that I can append stuff into and then return it as a string. In C++, a
non-const variable can be implicitly converted into a const. I know string is
an alias for const char. Is there a reason why it won't implicitly convert it?

I hesitate to use cast for this type of thing as it probably indicates I'm
doing something fundamentally wrong as I'm just starting to learn the language.