How to initialize immutable variables with an expression that throws an exception to catch?

[Nick Treleaven]

On Friday, 3 April 2020 at 06:56:27 UTC, FeepingCreature wrote:
> Maybe D could allow to initialize an immutable variable from 
> the try{} body if the catch{} body is statically known to exit 
> by return/throw?

Sounds like making try an expression:

immutable struct S { }
...
S s =
   try
     fun(); // implicit result
   catch (Exception)
     return;
call(s);

The above could also work if the catch block had the result and 
the try block was a terminating statement.

Another option would be a new expression that either yields the 
first expression if no exception was thrown, or it catches the 
exception and executes a statement or block that must terminate:

S s = fun() __or_catch (Exception e) return;
call(s);

(I have seen a similar form of expression for unwrapping optional 
values, terminating if the value doesn't exist in V language).

Not sure whether these are worth having yet as I've only just 
considered them ;-)