CommonType and non-built-in types

[ilya-stromberg]

On Tuesday, 1 October 2013 at 17:56:17 UTC, Dicebot wrote:
> Definition of common type is pretty simple - it is a type both 
> types can be implicitly converted to. For `int` and `BigInt` 
> common type should be `BigInt` if it was possible to define 
> that implicit conversion. AFAIK it is not possible and thus 
> they can't have common type.

Yes, we need implicit conversion support for usage cases like 
this.
May be only from build-in types to the user-defined as you said 
before, but it will be really useful.
I really don't know any usage example for implicit conversion 
from `int` to `BigInt` when it produces problems.