src/tools/clippy/tests/ui/eval_order_dependence.rs

   1
   2
   3
   4 #[warn(eval_order_dependence)]
   5 #[allow(unused_assignments, unused_variables, many_single_char_names, no_effect, dead_code, blacklisted_name)]
   6 fn main() {
   7     let mut x = 0;
   8     let a = { x = 1; 1 } + x;
   9
  10     // Example from iss#277
  11     x += { x = 20; 2 };
  12
  13     // Does it work in weird places?
  14     // ...in the base for a struct expression?
  15     struct Foo { a: i32, b: i32 };
  16     let base = Foo { a: 4, b: 5 };
  17     let foo = Foo { a: x, .. { x = 6; base } };
  18     // ...inside a closure?
  19     let closure = || {
  20         let mut x = 0;
  21         x += { x = 20; 2 };
  22     };
  23     // ...not across a closure?
  24     let mut y = 0;
  25     let b = (y, || { y = 1 });
  26
  27     // && and || evaluate left-to-right.
  28     let a = { x = 1; true } && (x == 3);
  29     let a = { x = 1; true } || (x == 3);
  30
  31     // Make sure we don't get confused by alpha conversion.
  32     let a = { let mut x = 1; x = 2; 1 } + x;
  33
  34     // No warning if we don't read the variable...
  35     x = { x = 20; 2 };
  36     // ...if the assignment is in a closure...
  37     let b = { || { x = 1; }; 1 } + x;
  38     // ... or the access is under an address.
  39     let b = ({ let p = &x; 1 }, { x = 1; x });
  40
  41     // Limitation: l-values other than simple variables don't trigger
  42     // the warning.
  43     let mut tup = (0, 0);
  44     let c = { tup.0 = 1; 1 } + tup.0;
  45     // Limitation: you can get away with a read under address-of.
  46     let mut z = 0;
  47     let b = (&{ z = x; x }, { x = 3; x });
  48 }