error: `~const` can only be applied to `#[const_trait]` traits
  --> $DIR/const_trait_impl.rs:34:16
   |
LL | impl<T: ~const Default> const A for T {
   |                ^^^^^^^

error: `~const` can only be applied to `#[const_trait]` traits
  --> $DIR/const_trait_impl.rs:40:16
   |
LL | impl<T: ~const Default + ~const Sup> const A for T {
   |                ^^^^^^^

error: `~const` can only be applied to `#[const_trait]` traits
  --> $DIR/const_trait_impl.rs:46:16
   |
LL | impl<T: ~const Default + ~const Sub> const A for T {
   |                ^^^^^^^

error[E0015]: cannot call non-const fn `<() as A>::a` in constants
  --> $DIR/const_trait_impl.rs:52:23
   |
LL | const _: () = assert!(<()>::a() == 42);
   |                       ^^^^^^^^^
   |
   = note: calls in constants are limited to constant functions, tuple structs and tuple variants
   = help: add `#![feature(effects)]` to the crate attributes to enable

error[E0015]: cannot call non-const fn `<u8 as A>::a` in constants
  --> $DIR/const_trait_impl.rs:53:23
   |
LL | const _: () = assert!(<u8>::a() == 3);
   |                       ^^^^^^^^^
   |
   = note: calls in constants are limited to constant functions, tuple structs and tuple variants
   = help: add `#![feature(effects)]` to the crate attributes to enable

error[E0015]: cannot call non-const fn `<u16 as A>::a` in constants
  --> $DIR/const_trait_impl.rs:54:23
   |
LL | const _: () = assert!(<u16>::a() == 2);
   |                       ^^^^^^^^^^
   |
   = note: calls in constants are limited to constant functions, tuple structs and tuple variants
   = help: add `#![feature(effects)]` to the crate attributes to enable

error: aborting due to 6 previous errors

For more information about this error, try `rustc --explain E0015`.