error: functions cannot be both `const` and `async`
  --> $DIR/fn-header-semantic-fail.rs:12:5
   |
LL |     const async unsafe extern "C" fn ff5() {} // OK.
   |     ^^^^^-^^^^^------------------------------
   |     |     |
   |     |     `async` because of this
   |     `const` because of this

error[E0706]: functions in traits cannot be declared `async`
  --> $DIR/fn-header-semantic-fail.rs:16:9
   |
LL |         async fn ft1();
   |         -----^^^^^^^^^^
   |         |
   |         `async` because of this
   |
   = note: `async` trait functions are not currently supported
   = note: consider using the `async-trait` crate: https://crates.io/crates/async-trait

error[E0379]: functions in traits cannot be declared const
  --> $DIR/fn-header-semantic-fail.rs:18:9
   |
LL |         const fn ft3();
   |         ^^^^^ functions in traits cannot be const

error[E0379]: functions in traits cannot be declared const
  --> $DIR/fn-header-semantic-fail.rs:20:9
   |
LL |         const async unsafe extern "C" fn ft5();
   |         ^^^^^ functions in traits cannot be const

error[E0706]: functions in traits cannot be declared `async`
  --> $DIR/fn-header-semantic-fail.rs:20:9
   |
LL |         const async unsafe extern "C" fn ft5();
   |         ^^^^^^-----^^^^^^^^^^^^^^^^^^^^^^^^^^^^
   |               |
   |               `async` because of this
   |
   = note: `async` trait functions are not currently supported
   = note: consider using the `async-trait` crate: https://crates.io/crates/async-trait

error: functions cannot be both `const` and `async`
  --> $DIR/fn-header-semantic-fail.rs:20:9
   |
LL |         const async unsafe extern "C" fn ft5();
   |         ^^^^^-^^^^^----------------------------
   |         |     |
   |         |     `async` because of this
   |         `const` because of this

error[E0706]: functions in traits cannot be declared `async`
  --> $DIR/fn-header-semantic-fail.rs:28:9
   |
LL |         async fn ft1() {}
   |         -----^^^^^^^^^^^^
   |         |
   |         `async` because of this
   |
   = note: `async` trait functions are not currently supported
   = note: consider using the `async-trait` crate: https://crates.io/crates/async-trait

error[E0379]: functions in traits cannot be declared const
  --> $DIR/fn-header-semantic-fail.rs:31:9
   |
LL |         const fn ft3() {}
   |         ^^^^^ functions in traits cannot be const

error[E0379]: functions in traits cannot be declared const
  --> $DIR/fn-header-semantic-fail.rs:33:9
   |
LL |         const async unsafe extern "C" fn ft5() {}
   |         ^^^^^ functions in traits cannot be const

error[E0706]: functions in traits cannot be declared `async`
  --> $DIR/fn-header-semantic-fail.rs:33:9
   |
LL |         const async unsafe extern "C" fn ft5() {}
   |         ^^^^^^-----^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
   |               |
   |               `async` because of this
   |
   = note: `async` trait functions are not currently supported
   = note: consider using the `async-trait` crate: https://crates.io/crates/async-trait

error: functions cannot be both `const` and `async`
  --> $DIR/fn-header-semantic-fail.rs:33:9
   |
LL |         const async unsafe extern "C" fn ft5() {}
   |         ^^^^^-^^^^^------------------------------
   |         |     |
   |         |     `async` because of this
   |         `const` because of this

error: functions cannot be both `const` and `async`
  --> $DIR/fn-header-semantic-fail.rs:45:9
   |
LL |         const async unsafe extern "C" fn fi5() {}
   |         ^^^^^-^^^^^------------------------------
   |         |     |
   |         |     `async` because of this
   |         `const` because of this

error: functions in `extern` blocks cannot have qualifiers
  --> $DIR/fn-header-semantic-fail.rs:50:18
   |
LL |     extern "C" {
   |     ---------- in this `extern` block
LL |         async fn fe1();
   |                  ^^^
   |
help: remove the qualifiers
   |
LL |         fn fe1();
   |         ~~

error: functions in `extern` blocks cannot have qualifiers
  --> $DIR/fn-header-semantic-fail.rs:51:19
   |
LL |     extern "C" {
   |     ---------- in this `extern` block
LL |         async fn fe1();
LL |         unsafe fn fe2();
   |                   ^^^
   |
help: remove the qualifiers
   |
LL |         fn fe2();
   |         ~~

error: functions in `extern` blocks cannot have qualifiers
  --> $DIR/fn-header-semantic-fail.rs:52:18
   |
LL |     extern "C" {
   |     ---------- in this `extern` block
...
LL |         const fn fe3();
   |                  ^^^
   |
help: remove the qualifiers
   |
LL |         fn fe3();
   |         ~~

error: functions in `extern` blocks cannot have qualifiers
  --> $DIR/fn-header-semantic-fail.rs:53:23
   |
LL |     extern "C" {
   |     ---------- in this `extern` block
...
LL |         extern "C" fn fe4();
   |                       ^^^
   |
help: remove the qualifiers
   |
LL |         fn fe4();
   |         ~~

error: functions in `extern` blocks cannot have qualifiers
  --> $DIR/fn-header-semantic-fail.rs:54:42
   |
LL |     extern "C" {
   |     ---------- in this `extern` block
...
LL |         const async unsafe extern "C" fn fe5();
   |                                          ^^^
   |
help: remove the qualifiers
   |
LL |         fn fe5();
   |         ~~

error: functions cannot be both `const` and `async`
  --> $DIR/fn-header-semantic-fail.rs:54:9
   |
LL |         const async unsafe extern "C" fn fe5();
   |         ^^^^^-^^^^^----------------------------
   |         |     |
   |         |     `async` because of this
   |         `const` because of this

error[E0053]: method `ft1` has an incompatible type for trait
  --> $DIR/fn-header-semantic-fail.rs:28:24
   |
LL |         async fn ft1() {}
   |                        ^
   |                        |
   |                        checked the `Output` of this `async fn`, found opaque type
   |                        expected `()`, found opaque type
   |
   = note: while checking the return type of the `async fn`
note: type in trait
  --> $DIR/fn-header-semantic-fail.rs:16:23
   |
LL |         async fn ft1();
   |                       ^
   = note: expected fn pointer `fn()`
              found fn pointer `fn() -> impl Future<Output = ()>`

error[E0053]: method `ft5` has an incompatible type for trait
  --> $DIR/fn-header-semantic-fail.rs:33:48
   |
LL |         const async unsafe extern "C" fn ft5() {}
   |                                                ^
   |                                                |
   |                                                checked the `Output` of this `async fn`, found opaque type
   |                                                expected `()`, found opaque type
   |
   = note: while checking the return type of the `async fn`
note: type in trait
  --> $DIR/fn-header-semantic-fail.rs:20:47
   |
LL |         const async unsafe extern "C" fn ft5();
   |                                               ^
   = note: expected fn pointer `unsafe extern "C" fn()`
              found fn pointer `unsafe extern "C" fn() -> impl Future<Output = ()>`

error: aborting due to 20 previous errors

Some errors have detailed explanations: E0053, E0379, E0706.
For more information about an error, try `rustc --explain E0053`.