error: defaults for type parameters are only allowed in `struct`, `enum`, `type`, or `trait` definitions
  --> $DIR/parameter-defaults.rs:10:12
   |
LL | const NONE<T = ()>: Option<T> = None::<T>;
   |            ^^^^^^

error[E0282]: type annotations needed for `Option<_>`
  --> $DIR/parameter-defaults.rs:13:9
   |
LL |     let _ = NONE;
   |         ^   ---- type must be known at this point
   |
help: consider giving this pattern a type, where the type for type parameter `T` is specified
   |
LL |     let _: Option<T> = NONE;
   |          +++++++++++

error: aborting due to 2 previous errors

For more information about this error, try `rustc --explain E0282`.