src/test/ui/nll/ty-outlives/ty-param-closure-outlives-from-return-type.rs

   1 // compile-flags:-Zverbose
   2
   3 #![allow(warnings)]
   4 #![feature(rustc_attrs)]
   5
   6 use std::fmt::Debug;
   7
   8 fn with_signature<'a, T, F>(x: Box<T>, op: F) -> Box<dyn Debug + 'a>
   9     where F: FnOnce(Box<T>) -> Box<dyn Debug + 'a>
  10 {
  11     op(x)
  12 }
  13
  14 #[rustc_regions]
  15 fn no_region<'a, T>(x: Box<T>) -> Box<dyn Debug + 'a>
  16 where
  17     T: Debug,
  18 {
  19     // Here, the closure winds up being required to prove that `T:
  20     // 'a`.  In principle, it could know that, except that it is
  21     // type-checked in a fully generic way, and hence it winds up with
  22     // a propagated requirement that `T: '_#2`, where `'_#2` appears
  23     // in the return type. The caller makes the mapping from `'_#2` to
  24     // `'a` (and subsequently reports an error).
  25
  26     with_signature(x, |y| y)
  27     //~^ ERROR the parameter type `T` may not live long enough
  28 }
  29
  30 fn correct_region<'a, T>(x: Box<T>) -> Box<Debug + 'a>
  31 where
  32     T: 'a + Debug,
  33 {
  34     x
  35 }
  36
  37 fn wrong_region<'a, 'b, T>(x: Box<T>) -> Box<Debug + 'a>
  38 where
  39     T: 'b + Debug,
  40 {
  41     x
  42     //~^ ERROR the parameter type `T` may not live long enough
  43 }
  44
  45 fn outlives_region<'a, 'b, T>(x: Box<T>) -> Box<Debug + 'a>
  46 where
  47     T: 'b + Debug,
  48     'b: 'a,
  49 {
  50     x
  51 }
  52
  53 fn main() {}