For me, a feature I'd really hope for is the elusive "if not let" (or however this gets named eventually), to let me escape the currently unavoidable clutches of Rust's rightwards drift and accruing mental context.
guard let x = ... else {
// must not fall through, so a return, break, throw, non-returning function call, etc. is required
}
// do something with x let x = match foo {
Some(x) => ...,
None => return // or break, etc.
};
// do something with x
// want to do this
if not let Some("pattern") = val {
doSomething();
}
// can instead do
if !matches!(val, Some("pattern")) {
doSomething();
} if !matches!(val, Some(let x)) let input: Option<usize> = Some(1);
if let Some(value) != input {
return 0;
}
// use value; such that value: usize = 1 let input: Option<usize> = Some(1);
let value = match input {
Some(x) => x,
_ => return 0,
};
// use value; such that value: usize = 1The point of a 'guard' clause is to visually distinguish between the "expected" and "unexpected" case. When I see a guard statement:
let input: Option<usize> = Some(1);
guard let Some(value) = input else {
return 0;
}
// use value; such that value: usize = 1