tests/ui/nll/issue-45696-no-variant-box-recur.rs

   1 // rust-lang/rust#45696: This test checks the compiler won't infinite loop when
   2 // you declare a variable of type `struct A(Box<A>, ...);` (which is impossible
   3 // to construct but *is* possible to declare; see also issues #4287, #44933,
   4 // and #52852).
   5
   6 // run-pass
   7
   8 // This test has structs and functions that are by definition unusable
   9 // all over the place, so just go ahead and allow dead_code
  10 #![allow(dead_code)]
  11
  12 // direct regular recursion with indirect ownership via box
  13 struct C { field: Box<C> }
  14
  15 // direct non-regular recursion with indirect ownership via box
  16 struct D { field: Box<(D, D)> }
  17
  18 // indirect regular recursion with indirect ownership via box.
  19 struct E { field: F }
  20 struct F { field: Box<E> }
  21
  22 // indirect non-regular recursion with indirect ownership via box.
  23 struct G { field: (H, H) }
  24 struct H { field: Box<G> }
  25
  26 // These enums are cases that are not currently hit by the
  27 // `visit_terminator_drop` recursion down a type's structural
  28 // definition.
  29 //
  30 // But it seems prudent to include them in this test as variants on
  31 // the above, in that they are similarly non-constructable data types
  32 // with destructors that would diverge.
  33 enum I { One(Box<I>) }
  34 enum J { One(Box<J>), Two(Box<J>) }
  35
  36 fn impossible_to_call_c(_c: C) { }
  37 fn impossible_to_call_d(_d: D) { }
  38 fn impossible_to_call_e(_e: E) { }
  39 fn impossible_to_call_f(_f: F) { }
  40 fn impossible_to_call_g(_g: G) { }
  41 fn impossible_to_call_h(_h: H) { }
  42 fn impossible_to_call_i(_i: I) { }
  43 fn impossible_to_call_j(_j: J) { }
  44
  45 fn main() {
  46
  47 }