Forbid dynamic arrays in boolean evaluation contexts

[Jacob Carlborg]

On 2013-03-24 23:10, bearophile wrote:
> A recent discussion in D.learn reminds me of an enhancement request of
> mine that is sleeping in Bugzilla since years:
>
> http://d.puremagic.com/issues/show_bug.cgi?id=4733
>
>
> The probles is that in D dynamic arrays can be non-null even when they
> are empty:
>
>
> import std.stdio;
> int[] foo() {
>      auto a = [1];
>      return a[0..0];
> }
> void main() {
>      auto data = foo();
>      if (data)
>          writeln("here");
> }
>
>
> This is dangerous, so in D the safe and idiomatic way to test for empty
> arrays is to use std.array.empty().
>
> So my proposal of Issue 4733 is to forbid (with the usual
> warning/deprecation intermediate steps) the use of dynamic arrays in a
> boolean context:
>
>
> void main() {
>      auto a = [1];
>      if (a) {} // error, forbidden.
> }
>
>
> So to test empty/null you have to use empty() or "is null":
>
> import std.array: empty;
> void main() {
>      auto a = [1];
>      if (a.empty) {} // OK
>      if (a is null) {} // OK
> }

I just started to use this in one place :(

if (auto a = getArray()) { }

getArray returns null if now array exists.

-- 
/Jacob Carlborg