error: `Option<usize>` is forbidden as the type of a const generic parameter
  --> $DIR/issue-68366.rs:9:25
   |
LL | struct Collatz<const N: Option<usize>>;
   |                         ^^^^^^^^^^^^^
   |
   = note: the only supported types are integers, `bool` and `char`
help: add `#![feature(adt_const_params)]` to the crate attributes to enable more complex and user defined types
   |
LL + #![feature(adt_const_params)]
   |

error[E0207]: the const parameter `N` is not constrained by the impl trait, self type, or predicates
  --> $DIR/issue-68366.rs:12:7
   |
LL | impl <const N: usize> Collatz<{Some(N)}> {}
   |       ^^^^^^^^^^^^^^ unconstrained const parameter
   |
   = note: expressions using a const parameter must map each value to a distinct output value
   = note: proving the result of expressions other than the parameter are unique is not supported

error[E0207]: the const parameter `N` is not constrained by the impl trait, self type, or predicates
  --> $DIR/issue-68366.rs:19:6
   |
LL | impl<const N: usize> Foo {}
   |      ^^^^^^^^^^^^^^ unconstrained const parameter
   |
   = note: expressions using a const parameter must map each value to a distinct output value
   = note: proving the result of expressions other than the parameter are unique is not supported

error: overly complex generic constant
  --> $DIR/issue-68366.rs:12:31
   |
LL | impl <const N: usize> Collatz<{Some(N)}> {}
   |                               ^-------^
   |                                |
   |                                struct/enum construction is not supported in generic constants
   |
   = help: consider moving this anonymous constant into a `const` function
   = note: this operation may be supported in the future

error: aborting due to 4 previous errors

For more information about this error, try `rustc --explain E0207`.