Things I found great about TypeScript that D could benefit from

[SimonN]

On Friday, 27 April 2018 at 19:17:14 UTC, w0rp wrote:
> The first feature I found really useful is the 
> --strictNullChecks option that TypeScript has. I hate null 
> dereferencing errors with a passion, and they have been the 
> number one source of bugs that I've seen.

> * Strict null checking is a winner, and you can use ordinary 
> syntax to handle this.
> That's it, let me know your thoughts.

Non-null class references are my #1 missing D feature. :-) When 
we don't have to worry about null-or-not, we have our mind free 
for the interesting problems. I love to peek around other 
languages and see how they tackle this problem. Thanks for the TS 
overview!

You advocate automatic narrowing inside if (x != null) even over 
Optional types. Is it because you find automatic narrowing 
cleaner than Optional? Or do you simply consider automatic 
narrowing a worthwhile addition whether or not a language has 
non-null + Optional?

```
void f(Optional!T x) { if (x !is null) g(x); }
void g(T x) { h(x); }
void h(T x) { writeln(x.myField); }
```

With a strictly non-nullable T, you can write `g` and `h` cleanly 
and null-safely. Without non-nullable types, even with implicit 
narrowing, both `g` and `h` would need an if/get or optional 
dispatch, complicating their definition.

-- Simon