error: defaults for const parameters are only allowed in `struct`, `enum`, `type`, or `trait` definitions
  --> $DIR/issue-105257.rs:5:12
   |
LL |     fn fnc<const N: usize = "">(&self) {}
   |            ^^^^^^^^^^^^^^^^^^^

error: defaults for const parameters are only allowed in `struct`, `enum`, `type`, or `trait` definitions
  --> $DIR/issue-105257.rs:6:12
   |
LL |     fn foo<const N: usize = { std::mem::size_of::<T>() }>(&self) {}
   |            ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^

error: aborting due to 2 previous errors