This is a minor issue, but it has worried me ever since floating-point enums were introduced. This code compiles on 2.049:

enum FloatEnum : float { A = float.max/2, B, C }

// but this assert fails!
static assert(FloatEnum.A != FloatEnum.B);

It's an obscure trap, but it's easy to fix.
-----------------

PATCH: enum.c, EnumDeclaration::semantic(), line 234.

            // Now set e to (elast + 1)
            e = new AddExp(em->loc, elast, new IntegerExp(em->loc, 1, Type::tint32));
            e = e->semantic(sce);
            e = e->castTo(sce, elast->type);
            e = e->optimize(WANTvalue | WANTinterpret);

+            // Check that e != elast (not always true for floats)
+            Expression *etest = new EqualExp(TOKequal, em->loc, e, elast);
+            etest = etest->semantic(sce);
+            etest = etest->optimize(WANTvalue | WANTinterpret);
+            if (etest->toInteger())
+                error("enum member %s has inexact value, due to loss of precision", em->toChars());

        }
        elast = e;
        em->value = e;