rust/tests/ui/nll/match-cfg-fake-edges.rs
2024-04-03 23:16:27 +02:00

120 lines
3.2 KiB
Rust

// Test that we have enough false edges to avoid exposing the exact matching
// algorithm in borrow checking.
#![feature(if_let_guard)]
#[rustfmt::skip]
fn all_patterns_are_tested() {
// Even though `x` is never actually moved out of, we don't want borrowck results to be based on
// whether MIR lowering reveals which patterns are unreachable.
let x = String::new();
match true {
_ => {},
_ => drop(x),
}
// Borrowck must not know the second arm is never run.
drop(x); //~ ERROR use of moved value
let x = String::new();
if let _ = true { //~ WARN irrefutable
} else {
drop(x)
}
// Borrowck must not know the else branch is never run.
drop(x); //~ ERROR use of moved value
let x = (String::new(), String::new());
match x {
(y, _) | (_, y) => (),
}
&x.0; //~ ERROR borrow of moved value
// Borrowck must not know the second pattern never matches.
&x.1; //~ ERROR borrow of moved value
let x = (String::new(), String::new());
let ((y, _) | (_, y)) = x;
&x.0; //~ ERROR borrow of moved value
// Borrowck must not know the second pattern never matches.
&x.1; //~ ERROR borrow of moved value
}
#[rustfmt::skip]
fn guard_always_precedes_arm(y: i32) {
// x should always be initialized, as the only way to reach the arm is
// through the guard.
let mut x;
match y {
0 | 2 if { x = 2; true } => x,
_ => 2,
};
let mut x;
match y {
_ => 2,
0 | 2 if { x = 2; true } => x,
};
let mut x;
match y {
0 | 2 if let Some(()) = { x = 2; Some(()) } => x,
_ => 2,
};
}
#[rustfmt::skip]
fn guard_may_be_skipped(y: i32) {
// Even though x *is* always initialized, we don't want to have borrowck results be based on
// whether MIR lowering reveals which patterns are exhaustive.
let x;
match y {
_ if { x = 2; true } => {},
// Borrowck must not know the guard is always run.
_ => drop(x), //~ ERROR used binding `x` is possibly-uninitialized
};
let x;
match y {
_ if { x = 2; true } => 1,
// Borrowck must not know the guard is always run.
_ if { x; false } => 2, //~ ERROR used binding `x` isn't initialized
_ => 3,
};
let x;
match y {
_ if let Some(()) = { x = 2; Some(()) } => 1,
_ if let Some(()) = { x; None } => 2, //~ ERROR used binding `x` isn't initialized
_ => 3,
};
}
#[rustfmt::skip]
fn guard_may_be_taken(y: bool) {
// Even though x *is* never moved before the use, we don't want to have
// borrowck results be based on whether patterns are disjoint.
let x = String::new();
match y {
false if { drop(x); true } => {},
// Borrowck must not know the guard is not run in the `true` case.
true => drop(x), //~ ERROR use of moved value: `x`
false => {},
};
// Fine in the other order.
let x = String::new();
match y {
true => drop(x),
false if { drop(x); true } => {},
false => {},
};
let x = String::new();
match y {
false if let Some(()) = { drop(x); Some(()) } => {},
true => drop(x), //~ ERROR use of moved value: `x`
false => {},
};
}
fn main() {}