On Sunday, 12 March 2023 at 13:07:58 UTC, DLearner wrote:
> Is it correct that this _single_ keyword is used to indicate _two_ quite different things:

No, it only actually does #2 in your thing. The type is optional meaning *any* storage class will work for type inference. `auto` is not special in variable declarations. (it can be special in other contexts though).

auto A = 5;
static A = 5;
const A = 5;

all the same.

On Sunday, 12 March 2023 at 13:27:05 UTC, Adam D Ruppe wrote:
> [...] *any* storage class will work for type inference. [...]

After heaving read [1] I immediately thought of this:

   void main ()
   {
      deprecated i = 3;
      i = 4;
   }
   $ dmd test.d
   test.d(4): Deprecation: variable `test.main.i` is deprecated

Does that make sense???

[1] https://issues.dlang.org/show_bug.cgi?id=7432
    Issue 7432 - DMD allows variables to be declared as pure

On 3/12/23 06:07, DLearner wrote:

> 1. As a shorthand to make the type of the variable being declared the
> same as the type on the right hand side of an initial assignment.

As Adam explained, D already has type inference without a special keyword.

However, some places where 'auto' (or 'const', etc.) appear is not only for "shorthand" but for necessity.

Some types cannot be spelled-out at all:

auto foo() {
    struct S {}
    return S();
}

void main() {
    pragma(msg, typeof(foo()));
    auto s = foo();
}

The name 'S' is available only inside 'foo', so code outside has no choice but to use 'auto' (or 'const', etc.)

Having said that, it is still possible to alias the returned type, which may be cumbersome in some cases because you may have to come up with a clean expression for attempting to call the function. In this case it's trivial because foo does not take any parameter:

    alias T = typeof(foo());
    T t;    // <-- There: I did not need to use 'auto'

Ali