src/test/ui/match/match-ref-mut-let-invariance.rs

   1 // Check that when making a ref mut binding with type `&mut T`, the
   2 // type `T` must match precisely the type `U` of the value being
   3 // matched, and in particular cannot be some supertype of `U`. Issue
   4 // #23116. This test focuses on a `let`.
   5
   6 #![allow(dead_code)]
   7 struct S<'b>(&'b i32);
   8 impl<'b> S<'b> {
   9     fn bar<'a>(&'a mut self) -> &'a mut &'a i32 {
  10         let ref mut x = self.0;
  11         x
  12         //~^ ERROR lifetime may not live long enough
  13     }
  14 }
  15
  16 fn main() {}