src/test/ui/traits/cache-reached-depth-ice.rs

   1 #![feature(rustc_attrs)]
   2
   3 // Test for a particular corner case where the evaluation
   4 // cache can get out of date. The problem here is that
   5 // when we cache C, we have observed that it reaches
   6 // to depth 2 (the node for B), but we later realize
   7 // that B itself depends on A (reached depth 0). We
   8 // failed to update the depth for C transitively, which
   9 // resulted in an assertion failure when it was referenced
  10 // from D.
  11 //
  12 // A (reached depth 0)
  13 //   E
  14 //      B // depth 2 -- reached depth = 0
  15 //          C // depth 3 -- reached depth = 2 (should be 0)
  16 //              B
  17 //          A // depth 0
  18 //   D (depth 1)
  19 //      C (cache -- reached depth = 2)
  20
  21 struct A {
  22     e: E,
  23     d: C,
  24 }
  25
  26 struct E {
  27     b: B,
  28 }
  29
  30 struct B {
  31     a: Option<Box<A>>,
  32     c: C,
  33 }
  34
  35 struct C {
  36     b: Option<Box<B>>,
  37 }
  38
  39 #[rustc_evaluate_where_clauses]
  40 fn test<X: ?Sized + Send>() {}
  41
  42 fn main() {
  43     test::<A>();
  44     //~^ ERROR evaluate(Binder(TraitPredicate(<A as std::marker::Send>, polarity:Positive), [])) = Ok(EvaluatedToOk)
  45 }