PhobosWatch: manifest => enum

[Janice Caron]

On 1/2/08, Russell Lewis <webmaster at villagersonline.com> wrote:
> I'll ignore for the moment the (very tricky) problem of assigning copies
> of const structs.  Just for basic types, we could easily solve this by
> requiring the syntax "const auto" when we wanted a constant:
>
>      const int X = 3;
>            auto i = X;
>      const auto j = X;
>      i = 4; // legal, typeof(i) is int

But typeof(i) /isn't/ int. typeof(i) is const(int). The problem is not
how to make a const copy of a const primitive - it's how to make a
mutable copy of a const primitive.

That's why Walter is introducing manifest constants:

    enum int x = 3;
    auto i = x; // typeof(i) is int
    const j = x; // typeof(i) is const(int)

and why I suggested allowing primitive types to have a .dup property

    const int x = 3;
    auto i = x.dup; // typeof(i) is int
    auto j = x; // typeof(i) is const(int)


> Doesn't it make sense that type deduction (which deals with how the
> variable was declared in the *past*) should be orthogonal from constness
> (which deals with how the variable will be used in the *future*)?

Type deduction only means that

    auto x = y;

is equivalent to

    typeof(y) x = y;

and if typeof(y) is const(int), well then, so will x be.