src/test/ui/nll/issue-16223.rs

   1 // Regression test for #16223: without NLL the `if let` construct together with
   2 // the nested box-structure of `Root` causes an unwanted collateral move.
   3
   4 // The exact error prevented here is:
   5 //
   6 // error[E0382]: use of collaterally moved value: `(root.boxed.rhs as SomeVariant::B).0`
   7 //   --> src/main.rs:55:29
   8 //    |
   9 // 56 |         lhs: SomeVariant::A(a),
  10 //    |                             - value moved here
  11 // 57 |         rhs: SomeVariant::B(b),
  12 //    |                             ^ value used here after move
  13 //    |
  14 //    = note: move occurs because the value has type `A`, which does not implement the `Copy` trait
  15
  16 // check-pass
  17
  18 #![feature(box_patterns)]
  19
  20 struct Root {
  21     boxed: Box<SetOfVariants>,
  22 }
  23
  24 struct SetOfVariants {
  25     lhs: SomeVariant,
  26     rhs: SomeVariant,
  27 }
  28
  29 enum SomeVariant {
  30     A(A),
  31     B(B),
  32 }
  33
  34 struct A(String);
  35 struct B(String);
  36
  37 fn main() {
  38     let root = Root {
  39         boxed: Box::new(SetOfVariants {
  40             lhs: SomeVariant::A(A(String::from("This is A"))),
  41             rhs: SomeVariant::B(B(String::from("This is B"))),
  42         }),
  43     };
  44     if let box SetOfVariants {
  45         lhs: SomeVariant::A(a),
  46         rhs: SomeVariant::B(b),
  47     } = root.boxed
  48     {
  49         println!("a = {}", a.0);
  50         println!("b = {}", b.0);
  51     }
  52 }