Add error note when trying fn as Fn trait

2 files changed, 53 insertions, 4 deletions

diff --git a/src/test/ui/rfcs/rfc-2396-target_feature-11/fn-traits.rs b/src/test/ui/rfcs/rfc-2396-target_feature-11/fn-traits.rs
index 58070b69bc1..5c838fd719c 100644
--- a/src/test/ui/rfcs/rfc-2396-target_feature-11/fn-traits.rs
+++ b/src/test/ui/rfcs/rfc-2396-target_feature-11/fn-traits.rs
@@ -5,6 +5,9 @@
 #[target_feature(enable = "avx")]
 fn foo() {}
 
+#[target_feature(enable = "avx")]
+unsafe fn foo_unsafe() {}
+
 fn call(f: impl Fn()) {
     f()
 }
@@ -21,4 +24,11 @@ fn main() {
     call(foo); //~ ERROR expected a `std::ops::Fn<()>` closure, found `fn() {foo}`
     call_mut(foo); //~ ERROR expected a `std::ops::FnMut<()>` closure, found `fn() {foo}`
     call_once(foo); //~ ERROR expected a `std::ops::FnOnce<()>` closure, found `fn() {foo}`
+
+    call(foo_unsafe);
+    //~^ ERROR expected a `std::ops::Fn<()>` closure, found `unsafe fn() {foo_unsafe}`
+    call_mut(foo_unsafe);
+    //~^ ERROR expected a `std::ops::FnMut<()>` closure, found `unsafe fn() {foo_unsafe}`
+    call_once(foo_unsafe);
+    //~^ ERROR expected a `std::ops::FnOnce<()>` closure, found `unsafe fn() {foo_unsafe}`
 }
diff --git a/src/test/ui/rfcs/rfc-2396-target_feature-11/fn-traits.stderr b/src/test/ui/rfcs/rfc-2396-target_feature-11/fn-traits.stderr
index 6dcf31b4c74..3ae85af76d3 100644
--- a/src/test/ui/rfcs/rfc-2396-target_feature-11/fn-traits.stderr
+++ b/src/test/ui/rfcs/rfc-2396-target_feature-11/fn-traits.stderr
@@ -1,5 +1,5 @@
 error[E0277]: expected a `std::ops::Fn<()>` closure, found `fn() {foo}`
-  --> $DIR/fn-traits.rs:21:10
+  --> $DIR/fn-traits.rs:24:10
    |
 LL | fn call(f: impl Fn()) {
    |                 ---- required by this bound in `call`
@@ -9,9 +9,10 @@ LL |     call(foo);
    |
    = help: the trait `std::ops::Fn<()>` is not implemented for `fn() {foo}`
    = note: wrap the `fn() {foo}` in a closure with no arguments: `|| { /* code */ }
+   = note: `fn() {foo}` has `#[target_feature]` and is unsafe to call
 
 error[E0277]: expected a `std::ops::FnMut<()>` closure, found `fn() {foo}`
-  --> $DIR/fn-traits.rs:22:14
+  --> $DIR/fn-traits.rs:25:14
    |
 LL | fn call_mut(f: impl FnMut()) {
    |                     ------- required by this bound in `call_mut`
@@ -21,9 +22,10 @@ LL |     call_mut(foo);
    |
    = help: the trait `std::ops::FnMut<()>` is not implemented for `fn() {foo}`
    = note: wrap the `fn() {foo}` in a closure with no arguments: `|| { /* code */ }
+   = note: `fn() {foo}` has `#[target_feature]` and is unsafe to call
 
 error[E0277]: expected a `std::ops::FnOnce<()>` closure, found `fn() {foo}`
-  --> $DIR/fn-traits.rs:23:15
+  --> $DIR/fn-traits.rs:26:15
    |
 LL | fn call_once(f: impl FnOnce()) {
    |                      -------- required by this bound in `call_once`
@@ -33,7 +35,44 @@ LL |     call_once(foo);
    |
    = help: the trait `std::ops::FnOnce<()>` is not implemented for `fn() {foo}`
    = note: wrap the `fn() {foo}` in a closure with no arguments: `|| { /* code */ }
+   = note: `fn() {foo}` has `#[target_feature]` and is unsafe to call
 
-error: aborting due to 3 previous errors
+error[E0277]: expected a `std::ops::Fn<()>` closure, found `unsafe fn() {foo_unsafe}`
+  --> $DIR/fn-traits.rs:28:10
+   |
+LL | fn call(f: impl Fn()) {
+   |                 ---- required by this bound in `call`
+...
+LL |     call(foo_unsafe);
+   |          ^^^^^^^^^^ expected an `Fn<()>` closure, found `unsafe fn() {foo_unsafe}`
+   |
+   = help: the trait `std::ops::Fn<()>` is not implemented for `unsafe fn() {foo_unsafe}`
+   = note: wrap the `unsafe fn() {foo_unsafe}` in a closure with no arguments: `|| { /* code */ }
+
+error[E0277]: expected a `std::ops::FnMut<()>` closure, found `unsafe fn() {foo_unsafe}`
+  --> $DIR/fn-traits.rs:30:14
+   |
+LL | fn call_mut(f: impl FnMut()) {
+   |                     ------- required by this bound in `call_mut`
+...
+LL |     call_mut(foo_unsafe);
+   |              ^^^^^^^^^^ expected an `FnMut<()>` closure, found `unsafe fn() {foo_unsafe}`
+   |
+   = help: the trait `std::ops::FnMut<()>` is not implemented for `unsafe fn() {foo_unsafe}`
+   = note: wrap the `unsafe fn() {foo_unsafe}` in a closure with no arguments: `|| { /* code */ }
+
+error[E0277]: expected a `std::ops::FnOnce<()>` closure, found `unsafe fn() {foo_unsafe}`
+  --> $DIR/fn-traits.rs:32:15
+   |
+LL | fn call_once(f: impl FnOnce()) {
+   |                      -------- required by this bound in `call_once`
+...
+LL |     call_once(foo_unsafe);
+   |               ^^^^^^^^^^ expected an `FnOnce<()>` closure, found `unsafe fn() {foo_unsafe}`
+   |
+   = help: the trait `std::ops::FnOnce<()>` is not implemented for `unsafe fn() {foo_unsafe}`
+   = note: wrap the `unsafe fn() {foo_unsafe}` in a closure with no arguments: `|| { /* code */ }
+
+error: aborting due to 6 previous errors
 
 For more information about this error, try `rustc --explain E0277`.