On 03/06/2012 04:46 PM, foobar wrote:
On Tuesday, 6 March 2012 at 10:19:19 UTC, Timon Gehr wrote:
This is quite close, but real support for non-nullable types means
that they are the default and checked statically, ideally using data
flow analysis.
I agree that non-nullable types should be made the default and
statically checked but data flow analysis here is redundant.
consider:
T foo = ..; // T is not-nullable
T? bar = ..; // T? is nullable
bar = foo; // legal implicit coercion T -> T?
foo = bar; // compile-time type mismatch error
//correct way:
if (bar) { // make sure bar isn't null
// compiler knows that cast(T)bar is safe
foo = bar;
}
Right. This example already demonstrates some simplistic data flow analysis.
of course we can employ additional syntax sugar such as:
foo = bar || <default_value>;
furthermore:
foo.method(); // legal
bar.method(); // compile-time error
it's all easily implementable in the type system.
Actually it requires some thinking because making initialization of
non-null fields safe is not entirely trivial.
For example:
http://pm.inf.ethz.ch/publications/getpdf.php/bibname/Own/id/SummersMuellerTR11.pdf
CTFE and static constructors solve that issue for static data.
