rust/tests/ui/eval_order_dependence.rs
2017-10-03 12:07:24 +02:00

48 lines
1.4 KiB
Rust

#[warn(eval_order_dependence)]
#[allow(unused_assignments, unused_variables, many_single_char_names, no_effect, dead_code, blacklisted_name)]
fn main() {
let mut x = 0;
let a = { x = 1; 1 } + x;
// Example from iss#277
x += { x = 20; 2 };
// Does it work in weird places?
// ...in the base for a struct expression?
struct Foo { a: i32, b: i32 };
let base = Foo { a: 4, b: 5 };
let foo = Foo { a: x, .. { x = 6; base } };
// ...inside a closure?
let closure = || {
let mut x = 0;
x += { x = 20; 2 };
};
// ...not across a closure?
let mut y = 0;
let b = (y, || { y = 1 });
// && and || evaluate left-to-right.
let a = { x = 1; true } && (x == 3);
let a = { x = 1; true } || (x == 3);
// Make sure we don't get confused by alpha conversion.
let a = { let mut x = 1; x = 2; 1 } + x;
// No warning if we don't read the variable...
x = { x = 20; 2 };
// ...if the assignment is in a closure...
let b = { || { x = 1; }; 1 } + x;
// ... or the access is under an address.
let b = ({ let p = &x; 1 }, { x = 1; x });
// Limitation: l-values other than simple variables don't trigger
// the warning.
let mut tup = (0, 0);
let c = { tup.0 = 1; 1 } + tup.0;
// Limitation: you can get away with a read under address-of.
let mut z = 0;
let b = (&{ z = x; x }, { x = 3; x });
}