support switch-case statements

[3esmit]

Abstract

Switch case is important for code cleanness. It's a common feature in all high level languages.

Motivation

While I undestand there is some complex edge cases to deal with on EVM for this control structure been implemented, it should start as simple as possible.

Specification

First iteration:

• uint256

enum MyEnum { A, B, C };
// (...)
MyEnum b = MyEnum.B;
switch(uint(b)){
     default:
         emit MyEvent();
     case uint(MyEnum.A):
         //(...)
         break;
     case uint(MyEnum.B):
        //(...)
        break;
}

Second iteration:

• enum type;

Third iteration:

• custom errors

Fouth iteration:

• complex structures

Whatever would cause a complexity or need more discussion to be porperly implemented should be left to a later iteration. In my example I used a default: without break;, if that would be difficult to solve, left it for a later iteration.

Backwards Compatibility