enum confusion

[Ali Çehreli]

On 5/8/22 18:50, Don Allen wrote:

 > I'm working on the
 > pre-hiatus project again

Welcome back!

 > So far, I've been mostly happy with my choice of D
 > and much of the work is done, with the core functionality working. The
 > code is more concise and readable than the C it came from. Performance
 > is absolutely fine. I love the fast compile times (dmd on a FreeBSD
 > system) and the ability to debug with gdb.

I am feeling panicky as DConf submission deadline is approaching (May 
15, 2022). I would love to watch your report on this project.

 > Named Enums,

Check.

 > Anonymous Enums

What a strange feature. :)

 > and Manifest Constants.

Check.

 > "Manifest constants are not
 > lvalues, meaning their address cannot be taken. They exist only in the
 > memory of the compiler." This can be read to suggest that the other two
 > types of enums described *are* lvalues

Yes, unclear wording but no, none of them are lvalues. Equivalent 
constructs that I can think of are 'static const' and 'static 
immutable'. Those would be evaluated at compile time but have addresses:

static const a = foo();
static immutable b = bar();

int foo() {
   return 42;
}

int bar() {
   return 43;
}

void main() {
   assert(&a != &b);
}

 > evaluating all enums at compile time, none of them
 > lvalues

YES! :)

Ali

P.S. While looking for traits related to rvalues and lvalues, I realized 
that at least isRvalueAssignable() and isLvalueAssignable() do not 
appear at the contents section on this page:

   https://dlang.org/phobos/std_traits.html

There are issues with Phobos documentation. :/