[OT] Some neat ideas from the Kotlin language

[Tobias Müller via Digitalmars-d]

rsw0x <anonymous at anonymous.com> wrote:
> On Saturday, 20 February 2016 at 09:40:40 UTC, Tobias Müller 
> wrote:
>> Yuxuan Shui <yshuiv7 at gmail.com> wrote:
>>> [...]
>> 
>> In Rust that would be:
>> 
>> let var : Option<i32> = ...;
>> if let Some(var) = var {
>> // You can use var here
>> }
>> 
>> It works for every enum (= tagged union), not just Option<T>
>> 
>> Swift also has "if let".
>> 
>> It's not much more verbose but more explicit.
>> Changing the type of a variable based on static analysis is 
>> just advanced
>> obfuscation. It hurts readability and the gain is questionable. 
>> At least it
>> only works for nullable types.
>> 
>> Tobi
> 
> D has this too, but only for nullable types afaik.
> 
> if(byte* ptr = someFunc()){
> //...
> }
> 
> 

That's not quite the same as there are no non-nullable pointers in D.
There's no guarantee from the type system that the byte* is not null and
there are no compiler checks involved.
It's a simple runtime check.

OTOH in the examples in Kotlin/Rust the variable 'var' changes its type
from 'int?' to plain 'int'.
In Kotlin this is done with static analysis, in Rust with rebinding of the
name.

Tobi