Enhance as or/and is operators is a good idea?

[orlys]

Scenario:

public class A {
    public static implicit operator B (A a) => ...;
} 
public class B { }

var a = new A();
var b = a as B;
if(a is B b)

Actual:

var a = new A();
var b = a as B; /* error CS0039 */
if (a is B b) { /* error CS8121 */ }

Is this a bad idea?
I personally feel that writing it down is better than using Reflection.

[huoyaoyuan]

See #1248

[jnm2]

I personally feel that writing it down is better than using Reflection.

The alternative is not reflection, the alternative is:

var a = new A();
var b = (B)a;
// 'if' makes no sense because it is a runtime check, but it statically known that A can be cast to B.