error[E0080]: erroneous constant used
  --> $DIR/assoc_const.rs:31:13
   |
LL |     let y = <String as Bar<Vec<u32>, String>>::F;
   |             ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ referenced constant has errors

warning: skipping const checks
   |
help: skipping check that does not even have a feature gate
  --> $DIR/assoc_const.rs:14:20
   |
LL |     const F: u32 = (U::X, 42).1;
   |                    ^^^^^^^^^^

error: aborting due to previous error; 1 warning emitted

For more information about this error, try `rustc --explain E0080`.
Future incompatibility report: Future breakage diagnostic:
warning: any use of this value will cause an error
  --> $SRC_DIR/core/src/ptr/mod.rs:LL:COL
   |
LL | pub unsafe fn drop_in_place<T: ?Sized>(to_drop: *mut T) {
   | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
   | |
   | calling non-const function `<Vec<u32> as Drop>::drop`
   | inside `std::ptr::drop_in_place::<Vec<u32>> - shim(Some(Vec<u32>))` at $SRC_DIR/core/src/ptr/mod.rs:LL:COL
   | inside `std::ptr::drop_in_place::<(Vec<u32>, u32)> - shim(Some((Vec<u32>, u32)))` at $SRC_DIR/core/src/ptr/mod.rs:LL:COL
   | inside `<String as Bar<Vec<u32>, String>>::F` at $DIR/assoc_const.rs:14:31
   |
  ::: $DIR/assoc_const.rs:14:5
   |
LL |     const F: u32 = (U::X, 42).1;
   |     ------------
   |
note: the lint level is defined here
  --> $DIR/assoc_const.rs:4:10
   |
LL | #![allow(const_err)]
   |          ^^^^^^^^^
   = warning: this was previously accepted by the compiler but is being phased out; it will become a hard error in a future release!
   = note: for more information, see issue #71800 <https://github.com/rust-lang/rust/issues/71800>