On Thursday, October 23, 2014 11:47:04 Shriramana Sharma via
Digitalmars-d-learn wrote:
Oh OK here it is:
http://dlang.org/deprecate.html#Variable%20shadowing%20inside%20functions
But it says "it is an error to use the feature" by 2.061 and
I'm using
2.066!
Doesn't the scope of that deprecation cover struct members too?
In
general it should be like "variables in inner scopes should not
shadow
those in outer scopes" irrespective of what the scopes are,
right?
Of course, for clarity we could add "except when the inner
scope is a
separate namespace", so it is made clear that enum/struct/class
members do not shadow outer variables...
Shadowing is only illegal when you're dealing with local
variables both declared within the same function with one in an
inner scope. It's perfectly legal when one variable is a local
variable and the other is a member variable, class/struct
variable, or module-level variable. Having a parameter shadow a
member variable is perfectly okay, because you can still
reference the member variable via the invisible this parameter.
Questions like this have come up and been discussed before, but
using the same parameter names as member variable names for
constructors is such a common practice that there would be quite
a bit of screaming if we didn't allow it. It's not going away,
and personally, I'd be very annoyed if it did. It's wonderfully
clear when the parameter name has the same name as the member
variable that it's going to initialize, and I'd hate to have to
come up with different parameter names just because someone was
worried about someone being foolish enough to do
x = x;
which is so obviously wrong that I don't know how much of anyone
could make that mistake. But simply making it illegal to assign a
variable to itself would solve that problem, and that arguably
should be done, since it's a essentially a no-op.
Regardless, a lot of people solve it by simply tagging their
member variables in some manner to indicate that they're member
variables and not local variables - e.g. _x instead of x.
- Jonathan M Davis
