Compile-time branching

<comptime_branch> ::= "comptime" <stmt> ;

Dependencies:

• <stmt>

The <comptime_branch> produces Stmt::ComptimeBranch(Box<Stmt>). The comptime keyword may precede any statement, but meaningful conditional compilation only occurs with branching statements (if, if matches, match).

Semantics

Since comptime must be resolved at compile time, the branching expression must itself be a literal, constant, or expression resolvable at compile time. Branches that are not matched will be removed from the compiled output.

use std::{
    builtin::HardFork,
    op::{tstore, tload, sstore, sload},
};
 
const SLOT: u256 = 0;
 
fn store(value: u256) {
    comptime if (@hardFork() == HardFork::Cancun) {
        tstore(SLOT, value);
    } else {
        sstore(SLOT, value);
    }
}
 
fn load() -> u256 {
    comptime match @hardFork() {
        HardFork::Cancun => tload(SLOT),
        _ => sload(SLOT),
    }
}