src/test/ui/closures/2229_closure_analysis/migrations/insignificant_drop_attr_migrations.fixed

   1 // run-rustfix
   2
   3 #![deny(rust_2021_incompatible_closure_captures)]
   4 //~^ NOTE: the lint level is defined here
   5 #![feature(rustc_attrs)]
   6 #![allow(unused)]
   7
   8 struct InsignificantDropPoint {
   9     x: i32,
  10     y: i32,
  11 }
  12
  13 impl Drop for InsignificantDropPoint {
  14     #[rustc_insignificant_dtor]
  15     fn drop(&mut self) {}
  16 }
  17
  18 struct SigDrop;
  19
  20 impl Drop for SigDrop {
  21     fn drop(&mut self) {}
  22 }
  23
  24 struct GenericStruct<T>(T, T);
  25
  26 struct Wrapper<T>(GenericStruct<T>, i32);
  27
  28 impl<T> Drop for GenericStruct<T> {
  29     #[rustc_insignificant_dtor]
  30     fn drop(&mut self) {}
  31 }
  32
  33 // `SigDrop` implements drop and therefore needs to be migrated.
  34 fn significant_drop_needs_migration() {
  35     let t = (SigDrop {}, SigDrop {});
  36
  37     let c = || { let _ = &t;
  38         //~^ ERROR: drop order
  39         //~| NOTE: for more information, see
  40         //~| HELP: add a dummy let to cause `t` to be fully captured
  41         let _t = t.0;
  42         //~^ NOTE: in Rust 2018, closure captures all of `t`, but in Rust 2021, it only captures `t.0`
  43     };
  44
  45     c();
  46 }
  47 //~^ NOTE: in Rust 2018, `t` would be dropped here, but in Rust 2021, only `t.0` would be dropped here alongside the closure
  48
  49 // Even if a type implements an insignificant drop, if it's
  50 // elements have a significant drop then the overall type is
  51 // consdered to have an significant drop. Since the elements
  52 // of `GenericStruct` implement drop, migration is required.
  53 fn generic_struct_with_significant_drop_needs_migration() {
  54     let t = Wrapper(GenericStruct(SigDrop {}, SigDrop {}), 5);
  55
  56     // move is used to force i32 to be copied instead of being a ref
  57     let c = move || { let _ = &t;
  58         //~^ ERROR: drop order
  59         //~| NOTE: for more information, see
  60         //~| HELP: add a dummy let to cause `t` to be fully captured
  61         let _t = t.1;
  62         //~^ NOTE: in Rust 2018, closure captures all of `t`, but in Rust 2021, it only captures `t.1`
  63     };
  64
  65     c();
  66 }
  67 //~^ NOTE: in Rust 2018, `t` would be dropped here, but in Rust 2021, only `t.1` would be dropped here alongside the closure
  68
  69 fn main() {
  70     significant_drop_needs_migration();
  71     generic_struct_with_significant_drop_needs_migration();
  72 }