error: expected `mut` or `const` keyword in raw pointer type
  --> $DIR/double-pointer.rs:4:15
   |
LL |     let dptr: **const i32 = &ptr;
   |               ^
   |
help: add `mut` or `const` here
   |
LL |     let dptr: *mut *const i32 = &ptr;
   |                +++
LL |     let dptr: *const *const i32 = &ptr;
   |                +++++

error: aborting due to 1 previous error