error: generic parameters may not be used in const operations
  --> $DIR/trivial-const-arg-nested-braces.rs:4:35
   |
LL | fn foo<const N: usize>() -> A<{ { N } }> {
   |                                   ^ cannot perform const operation using `N`
   |
   = help: const parameters may only be used as standalone arguments, i.e. `N`
   = help: add `#![feature(generic_const_exprs)]` to allow generic const expressions

error: aborting due to 1 previous error