error[E0635]: unknown feature `const_fn_trait_ref_impls`
  --> $DIR/fn_trait_refs.rs:3:12
   |
LL | #![feature(const_fn_trait_ref_impls)]
   |            ^^^^^^^^^^^^^^^^^^^^^^^^

error: `~const` can only be applied to `#[const_trait]` traits
  --> $DIR/fn_trait_refs.rs:15:15
   |
LL |     T: ~const Fn<()> + ~const Destruct,
   |               ^^^^^^

error: `~const` can only be applied to `#[const_trait]` traits
  --> $DIR/fn_trait_refs.rs:15:15
   |
LL |     T: ~const Fn<()> + ~const Destruct,
   |               ^^^^^^
   |
   = note: duplicate diagnostic emitted due to `-Z deduplicate-diagnostics=no`

error: `~const` can only be applied to `#[const_trait]` traits
  --> $DIR/fn_trait_refs.rs:22:15
   |
LL |     T: ~const FnMut<()> + ~const Destruct,
   |               ^^^^^^^^^

error: `~const` can only be applied to `#[const_trait]` traits
  --> $DIR/fn_trait_refs.rs:22:15
   |
LL |     T: ~const FnMut<()> + ~const Destruct,
   |               ^^^^^^^^^
   |
   = note: duplicate diagnostic emitted due to `-Z deduplicate-diagnostics=no`

error: `~const` can only be applied to `#[const_trait]` traits
  --> $DIR/fn_trait_refs.rs:29:15
   |
LL |     T: ~const FnOnce<()>,
   |               ^^^^^^^^^^

error: `~const` can only be applied to `#[const_trait]` traits
  --> $DIR/fn_trait_refs.rs:29:15
   |
LL |     T: ~const FnOnce<()>,
   |               ^^^^^^^^^^
   |
   = note: duplicate diagnostic emitted due to `-Z deduplicate-diagnostics=no`

error: `~const` can only be applied to `#[const_trait]` traits
  --> $DIR/fn_trait_refs.rs:36:15
   |
LL |     T: ~const Fn<()> + ~const Destruct,
   |               ^^^^^^

error: `~const` can only be applied to `#[const_trait]` traits
  --> $DIR/fn_trait_refs.rs:36:15
   |
LL |     T: ~const Fn<()> + ~const Destruct,
   |               ^^^^^^
   |
   = note: duplicate diagnostic emitted due to `-Z deduplicate-diagnostics=no`

error: `~const` can only be applied to `#[const_trait]` traits
  --> $DIR/fn_trait_refs.rs:50:15
   |
LL |     T: ~const FnMut<()> + ~const Destruct,
   |               ^^^^^^^^^

error: `~const` can only be applied to `#[const_trait]` traits
  --> $DIR/fn_trait_refs.rs:50:15
   |
LL |     T: ~const FnMut<()> + ~const Destruct,
   |               ^^^^^^^^^
   |
   = note: duplicate diagnostic emitted due to `-Z deduplicate-diagnostics=no`

error[E0015]: cannot call non-const closure in constant functions
  --> $DIR/fn_trait_refs.rs:17:5
   |
LL |     f()
   |     ^^^
   |
   = note: calls in constant functions are limited to constant functions, tuple structs and tuple variants
   = help: add `#![feature(effects)]` to the crate attributes to enable
help: consider further restricting this bound
   |
LL |     T: ~const Fn<()> + ~const Destruct + ~const std::ops::Fn<()>,
   |                                        +++++++++++++++++++++++++

error[E0493]: destructor of `T` cannot be evaluated at compile-time
  --> $DIR/fn_trait_refs.rs:13:23
   |
LL | const fn tester_fn<T>(f: T) -> T::Output
   |                       ^ the destructor for this type cannot be evaluated in constant functions
...
LL | }
   | - value is dropped here

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

error[E0493]: destructor of `T` cannot be evaluated at compile-time
  --> $DIR/fn_trait_refs.rs:20:27
   |
LL | const fn tester_fn_mut<T>(mut f: T) -> T::Output
   |                           ^^^^^ the destructor for this type cannot be evaluated in constant functions
...
LL | }
   | - value is dropped here

error[E0015]: cannot call non-const closure in constant functions
  --> $DIR/fn_trait_refs.rs:31:5
   |
LL |     f()
   |     ^^^
   |
   = note: calls in constant functions are limited to constant functions, tuple structs and tuple variants
   = help: add `#![feature(effects)]` to the crate attributes to enable
help: consider further restricting this bound
   |
LL |     T: ~const FnOnce<()> + ~const std::ops::FnOnce<()>,
   |                          +++++++++++++++++++++++++++++

error[E0493]: destructor of `T` cannot be evaluated at compile-time
  --> $DIR/fn_trait_refs.rs:34:21
   |
LL | const fn test_fn<T>(mut f: T) -> (T::Output, T::Output, T::Output)
   |                     ^^^^^ the destructor for this type cannot be evaluated in constant functions
...
LL | }
   | - value is dropped here

error[E0493]: destructor of `T` cannot be evaluated at compile-time
  --> $DIR/fn_trait_refs.rs:48:25
   |
LL | const fn test_fn_mut<T>(mut f: T) -> (T::Output, T::Output)
   |                         ^^^^^ the destructor for this type cannot be evaluated in constant functions
...
LL | }
   | - value is dropped here

error[E0015]: cannot call non-const operator in constants
  --> $DIR/fn_trait_refs.rs:72:17
   |
LL |         assert!(test_one == (1, 1, 1));
   |                 ^^^^^^^^^^^^^^^^^^^^^
   |
   = 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 operator in constants
  --> $DIR/fn_trait_refs.rs:75:17
   |
LL |         assert!(test_two == (2, 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 20 previous errors

Some errors have detailed explanations: E0015, E0493, E0635.
For more information about an error, try `rustc --explain E0015`.