src/test/ui/try-block/try-block-maybe-bad-lifetime.rs

   1 // compile-flags: --edition 2018
   2
   3 #![feature(try_blocks)]
   4
   5 #![inline(never)]
   6 fn do_something_with<T>(_x: T) {}
   7
   8 // This test checks that borrows made and returned inside try blocks are properly constrained
   9 pub fn main() {
  10     {
  11         // Test that a borrow which *might* be returned still freezes its referent
  12         let mut i = 222;
  13         let x: Result<&i32, ()> = try {
  14             Err(())?;
  15             &i
  16         };
  17         i = 0; //~ ERROR cannot assign to `i` because it is borrowed
  18         let _ = i;
  19         do_something_with(x);
  20     }
  21
  22     {
  23         let x = String::new();
  24         let _y: Result<(), ()> = try {
  25             Err(())?;
  26             ::std::mem::drop(x);
  27         };
  28         println!("{}", x); //~ ERROR borrow of moved value: `x`
  29     }
  30
  31     {
  32         // Test that a borrow which *might* be assigned to an outer variable still freezes
  33         // its referent
  34         let mut i = 222;
  35         let mut j = &-1;
  36         let _x: Result<(), ()> = try {
  37             Err(())?;
  38             j = &i;
  39         };
  40         i = 0; //~ ERROR cannot assign to `i` because it is borrowed
  41         let _ = i;
  42         do_something_with(j);
  43     }
  44 }