error: `~const` can only be applied to `#[const_trait]` traits
  --> $DIR/const-closures.rs:8:19
   |
LL |         F: ~const FnOnce() -> u8,
   |                   ^^^^^^^^^^^^^^

error: `~const` can only be applied to `#[const_trait]` traits
  --> $DIR/const-closures.rs:9:19
   |
LL |         F: ~const FnMut() -> u8,
   |                   ^^^^^^^^^^^^^

error: `~const` can only be applied to `#[const_trait]` traits
  --> $DIR/const-closures.rs:10:19
   |
LL |         F: ~const Fn() -> u8,
   |                   ^^^^^^^^^^

error: `~const` can only be applied to `#[const_trait]` traits
  --> $DIR/const-closures.rs:23:27
   |
LL | const fn answer<F: ~const Fn() -> u8>(f: &F) -> u8 {
   |                           ^^^^^^^^^^

error[E0015]: cannot call non-const closure in constant functions
  --> $DIR/const-closures.rs:24:5
   |
LL |     f() + f()
   |     ^^^
   |
   = note: calls in constant functions are limited to constant functions, tuple structs and tuple variants
help: consider further restricting this bound
   |
LL | const fn answer<F: ~const Fn() -> u8 + ~const Fn()>(f: &F) -> u8 {
   |                                      +++++++++++++
help: add `#![feature(effects)]` to the crate attributes to enable
   |
LL + #![feature(effects)]
   |

error[E0015]: cannot call non-const closure in constant functions
  --> $DIR/const-closures.rs:24:11
   |
LL |     f() + f()
   |           ^^^
   |
   = note: calls in constant functions are limited to constant functions, tuple structs and tuple variants
help: consider further restricting this bound
   |
LL | const fn answer<F: ~const Fn() -> u8 + ~const Fn()>(f: &F) -> u8 {
   |                                      +++++++++++++
help: add `#![feature(effects)]` to the crate attributes to enable
   |
LL + #![feature(effects)]
   |

error[E0015]: cannot call non-const closure in constant functions
  --> $DIR/const-closures.rs:12:5
   |
LL |     f() * 7
   |     ^^^
   |
   = note: calls in constant functions are limited to constant functions, tuple structs and tuple variants
help: consider further restricting this bound
   |
LL |         F: ~const FnOnce() -> u8 + ~const Fn(),
   |                                  +++++++++++++
help: add `#![feature(effects)]` to the crate attributes to enable
   |
LL + #![feature(effects)]
   |

error: aborting due to 7 previous errors

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