On Saturday, 6 July 2013 at 13:30:02 UTC, TommiT wrote:

Some more details of this proposed feature:

inout(T) foo(inout T)(T a, T b)
{
    return var;
}

void bar(inout T)(T a, T b)
{
    a = b;
}

void main()
{
    const int con;
    immutable int imm;

    foo(con, con); // OK (returns const int)
    foo(con, imm); // Error: returned inout(T) is ambiguous

    bar(con, con); // OK
    bar(con, imm); // OK (no ambiguity because inout not used)
}

Another approach, if we wanted a different syntax, would be to add a new keyword 'mutable'. Like immutable overrides const, mutable would override both const and immutable:

static assert(is(mutable(const(int)) == int));
static assert(is(mutable(immutable(int)) == int));

Here's how it would look:

T foo(T)(mutable(T) a, mutable(T) b)
{
    a = b = 123;
    return a;

}

void main()
{
    const int con;
    immutable int imm;

    foo(con, con); // OK (returns const int)

    foo(con, imm); // Error: T is ambiguous
}