#[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 }); }