diff --git a/src/test/ui/extern/extern-wrong-value-type.stderr b/src/test/ui/extern/extern-wrong-value-type.stderr
index 35e0d68e46aa..0d8185839ccb 100644
--- a/src/test/ui/extern/extern-wrong-value-type.stderr
+++ b/src/test/ui/extern/extern-wrong-value-type.stderr
@@ -1,9 +1,11 @@
-error[E0277]: the trait bound `extern "C" fn() {f}: std::ops::Fn<()>` is not satisfied
+error[E0277]: expected a `std::ops::Fn<()>` closure, found `extern "C" fn() {f}`
   --> $DIR/extern-wrong-value-type.rs:19:5
    |
 LL |     is_fn(f);
-   |     ^^^^^ the trait `std::ops::Fn<()>` is not implemented for `extern "C" fn() {f}`
+   |     ^^^^^ expected an `Fn<()>` closure, found `extern "C" fn() {f}`
    |
+   = help: the trait `std::ops::Fn<()>` is not implemented for `extern "C" fn() {f}`
+   = note: wrap the `extern "C" fn() {f}` in a closure with no arguments: `|| { /* code */ }
 note: required by `is_fn`
   --> $DIR/extern-wrong-value-type.rs:14:1
    |
diff --git a/src/test/ui/fn/fn-trait-formatting.stderr b/src/test/ui/fn/fn-trait-formatting.stderr
index 5bf1ed76d5f4..198b343cdd3e 100644
--- a/src/test/ui/fn/fn-trait-formatting.stderr
+++ b/src/test/ui/fn/fn-trait-formatting.stderr
@@ -25,15 +25,13 @@ LL |     let _: () = (box || -> isize { unimplemented!() }) as Box<FnMut() -> is
    = note: expected type `()`
               found type `std::boxed::Box<dyn std::ops::FnMut() -> isize>`
 
-error[E0277]: the trait bound `{integer}: std::ops::Fn<(isize,)>` is not satisfied
+error[E0277]: expected a `std::ops::Fn<(isize,)>` closure, found `{integer}`
   --> $DIR/fn-trait-formatting.rs:29:5
    |
 LL |     needs_fn(1);
-   |     ^^^^^^^^ the trait `std::ops::Fn<(isize,)>` is not implemented for `{integer}`
+   |     ^^^^^^^^ expected an `Fn<(isize,)>` closure, found `{integer}`
    |
-   = help: the following implementations were found:
-             <&'a F as std::ops::Fn<A>>
-             <core::str::LinesAnyMap as std::ops::Fn<(&'a str,)>>
+   = help: the trait `std::ops::Fn<(isize,)>` is not implemented for `{integer}`
 note: required by `needs_fn`
   --> $DIR/fn-trait-formatting.rs:13:1
    |
diff --git a/src/test/ui/unboxed-closures/unboxed-closures-fnmut-as-fn.stderr b/src/test/ui/unboxed-closures/unboxed-closures-fnmut-as-fn.stderr
index 95aa3f15b764..e5e66efcaa2c 100644
--- a/src/test/ui/unboxed-closures/unboxed-closures-fnmut-as-fn.stderr
+++ b/src/test/ui/unboxed-closures/unboxed-closures-fnmut-as-fn.stderr
@@ -1,9 +1,10 @@
-error[E0277]: the trait bound `S: std::ops::Fn<(isize,)>` is not satisfied
+error[E0277]: expected a `std::ops::Fn<(isize,)>` closure, found `S`
   --> $DIR/unboxed-closures-fnmut-as-fn.rs:38:13
    |
 LL |     let x = call_it(&S, 22);
-   |             ^^^^^^^ the trait `std::ops::Fn<(isize,)>` is not implemented for `S`
+   |             ^^^^^^^ expected an `Fn<(isize,)>` closure, found `S`
    |
+   = help: the trait `std::ops::Fn<(isize,)>` is not implemented for `S`
 note: required by `call_it`
   --> $DIR/unboxed-closures-fnmut-as-fn.rs:33:1
    |
diff --git a/src/test/ui/unboxed-closures/unboxed-closures-unsafe-extern-fn.stderr b/src/test/ui/unboxed-closures/unboxed-closures-unsafe-extern-fn.stderr
index 16b2b11ad7b4..7c76c10443af 100644
--- a/src/test/ui/unboxed-closures/unboxed-closures-unsafe-extern-fn.stderr
+++ b/src/test/ui/unboxed-closures/unboxed-closures-unsafe-extern-fn.stderr
@@ -1,33 +1,36 @@
-error[E0277]: the trait bound `for<'r> for<'s> unsafe fn(&'s isize) -> isize {square}: std::ops::Fn<(&'r isize,)>` is not satisfied
+error[E0277]: expected a `std::ops::Fn<(&isize,)>` closure, found `for<'r> unsafe fn(&'r isize) -> isize {square}`
   --> $DIR/unboxed-closures-unsafe-extern-fn.rs:22:13
    |
 LL |     let x = call_it(&square, 22);
-   |             ^^^^^^^ the trait `for<'r> std::ops::Fn<(&'r isize,)>` is not implemented for `for<'r> unsafe fn(&'r isize) -> isize {square}`
+   |             ^^^^^^^ expected an `Fn<(&isize,)>` closure, found `for<'r> unsafe fn(&'r isize) -> isize {square}`
    |
+   = help: the trait `for<'r> std::ops::Fn<(&'r isize,)>` is not implemented for `for<'r> unsafe fn(&'r isize) -> isize {square}`
 note: required by `call_it`
   --> $DIR/unboxed-closures-unsafe-extern-fn.rs:17:1
    |
 LL | fn call_it<F:Fn(&isize)->isize>(_: &F, _: isize) -> isize { 0 }
    | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
 
-error[E0277]: the trait bound `for<'r> for<'s> unsafe fn(&'s isize) -> isize {square}: std::ops::FnMut<(&'r isize,)>` is not satisfied
+error[E0277]: expected a `std::ops::FnMut<(&isize,)>` closure, found `for<'r> unsafe fn(&'r isize) -> isize {square}`
   --> $DIR/unboxed-closures-unsafe-extern-fn.rs:27:13
    |
 LL |     let y = call_it_mut(&mut square, 22);
-   |             ^^^^^^^^^^^ the trait `for<'r> std::ops::FnMut<(&'r isize,)>` is not implemented for `for<'r> unsafe fn(&'r isize) -> isize {square}`
+   |             ^^^^^^^^^^^ expected an `FnMut<(&isize,)>` closure, found `for<'r> unsafe fn(&'r isize) -> isize {square}`
    |
+   = help: the trait `for<'r> std::ops::FnMut<(&'r isize,)>` is not implemented for `for<'r> unsafe fn(&'r isize) -> isize {square}`
 note: required by `call_it_mut`
   --> $DIR/unboxed-closures-unsafe-extern-fn.rs:18:1
    |
 LL | fn call_it_mut<F:FnMut(&isize)->isize>(_: &mut F, _: isize) -> isize { 0 }
    | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
 
-error[E0277]: the trait bound `for<'r> for<'s> unsafe fn(&'s isize) -> isize {square}: std::ops::FnOnce<(&'r isize,)>` is not satisfied
+error[E0277]: expected a `std::ops::FnOnce<(&isize,)>` closure, found `for<'r> unsafe fn(&'r isize) -> isize {square}`
   --> $DIR/unboxed-closures-unsafe-extern-fn.rs:32:13
    |
 LL |     let z = call_it_once(square, 22);
-   |             ^^^^^^^^^^^^ the trait `for<'r> std::ops::FnOnce<(&'r isize,)>` is not implemented for `for<'r> unsafe fn(&'r isize) -> isize {square}`
+   |             ^^^^^^^^^^^^ expected an `FnOnce<(&isize,)>` closure, found `for<'r> unsafe fn(&'r isize) -> isize {square}`
    |
+   = help: the trait `for<'r> std::ops::FnOnce<(&'r isize,)>` is not implemented for `for<'r> unsafe fn(&'r isize) -> isize {square}`
 note: required by `call_it_once`
   --> $DIR/unboxed-closures-unsafe-extern-fn.rs:19:1
    |
diff --git a/src/test/ui/unboxed-closures/unboxed-closures-wrong-abi.stderr b/src/test/ui/unboxed-closures/unboxed-closures-wrong-abi.stderr
index 6e5e1b928a2c..18ade48de664 100644
--- a/src/test/ui/unboxed-closures/unboxed-closures-wrong-abi.stderr
+++ b/src/test/ui/unboxed-closures/unboxed-closures-wrong-abi.stderr
@@ -1,33 +1,36 @@
-error[E0277]: the trait bound `for<'r> for<'s> extern "C" fn(&'s isize) -> isize {square}: std::ops::Fn<(&'r isize,)>` is not satisfied
+error[E0277]: expected a `std::ops::Fn<(&isize,)>` closure, found `for<'r> extern "C" fn(&'r isize) -> isize {square}`
   --> $DIR/unboxed-closures-wrong-abi.rs:22:13
    |
 LL |     let x = call_it(&square, 22);
-   |             ^^^^^^^ the trait `for<'r> std::ops::Fn<(&'r isize,)>` is not implemented for `for<'r> extern "C" fn(&'r isize) -> isize {square}`
+   |             ^^^^^^^ expected an `Fn<(&isize,)>` closure, found `for<'r> extern "C" fn(&'r isize) -> isize {square}`
    |
+   = help: the trait `for<'r> std::ops::Fn<(&'r isize,)>` is not implemented for `for<'r> extern "C" fn(&'r isize) -> isize {square}`
 note: required by `call_it`
   --> $DIR/unboxed-closures-wrong-abi.rs:17:1
    |
 LL | fn call_it<F:Fn(&isize)->isize>(_: &F, _: isize) -> isize { 0 }
    | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
 
-error[E0277]: the trait bound `for<'r> for<'s> extern "C" fn(&'s isize) -> isize {square}: std::ops::FnMut<(&'r isize,)>` is not satisfied
+error[E0277]: expected a `std::ops::FnMut<(&isize,)>` closure, found `for<'r> extern "C" fn(&'r isize) -> isize {square}`
   --> $DIR/unboxed-closures-wrong-abi.rs:27:13
    |
 LL |     let y = call_it_mut(&mut square, 22);
-   |             ^^^^^^^^^^^ the trait `for<'r> std::ops::FnMut<(&'r isize,)>` is not implemented for `for<'r> extern "C" fn(&'r isize) -> isize {square}`
+   |             ^^^^^^^^^^^ expected an `FnMut<(&isize,)>` closure, found `for<'r> extern "C" fn(&'r isize) -> isize {square}`
    |
+   = help: the trait `for<'r> std::ops::FnMut<(&'r isize,)>` is not implemented for `for<'r> extern "C" fn(&'r isize) -> isize {square}`
 note: required by `call_it_mut`
   --> $DIR/unboxed-closures-wrong-abi.rs:18:1
    |
 LL | fn call_it_mut<F:FnMut(&isize)->isize>(_: &mut F, _: isize) -> isize { 0 }
    | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
 
-error[E0277]: the trait bound `for<'r> for<'s> extern "C" fn(&'s isize) -> isize {square}: std::ops::FnOnce<(&'r isize,)>` is not satisfied
+error[E0277]: expected a `std::ops::FnOnce<(&isize,)>` closure, found `for<'r> extern "C" fn(&'r isize) -> isize {square}`
   --> $DIR/unboxed-closures-wrong-abi.rs:32:13
    |
 LL |     let z = call_it_once(square, 22);
-   |             ^^^^^^^^^^^^ the trait `for<'r> std::ops::FnOnce<(&'r isize,)>` is not implemented for `for<'r> extern "C" fn(&'r isize) -> isize {square}`
+   |             ^^^^^^^^^^^^ expected an `FnOnce<(&isize,)>` closure, found `for<'r> extern "C" fn(&'r isize) -> isize {square}`
    |
+   = help: the trait `for<'r> std::ops::FnOnce<(&'r isize,)>` is not implemented for `for<'r> extern "C" fn(&'r isize) -> isize {square}`
 note: required by `call_it_once`
   --> $DIR/unboxed-closures-wrong-abi.rs:19:1
    |
diff --git a/src/test/ui/unboxed-closures/unboxed-closures-wrong-arg-type-extern-fn.stderr b/src/test/ui/unboxed-closures/unboxed-closures-wrong-arg-type-extern-fn.stderr
index 5c2e73f57160..f27b73017a28 100644
--- a/src/test/ui/unboxed-closures/unboxed-closures-wrong-arg-type-extern-fn.stderr
+++ b/src/test/ui/unboxed-closures/unboxed-closures-wrong-arg-type-extern-fn.stderr
@@ -1,33 +1,36 @@
-error[E0277]: the trait bound `for<'r> unsafe fn(isize) -> isize {square}: std::ops::Fn<(&'r isize,)>` is not satisfied
+error[E0277]: expected a `std::ops::Fn<(&isize,)>` closure, found `unsafe fn(isize) -> isize {square}`
   --> $DIR/unboxed-closures-wrong-arg-type-extern-fn.rs:23:13
    |
 LL |     let x = call_it(&square, 22);
-   |             ^^^^^^^ the trait `for<'r> std::ops::Fn<(&'r isize,)>` is not implemented for `unsafe fn(isize) -> isize {square}`
+   |             ^^^^^^^ expected an `Fn<(&isize,)>` closure, found `unsafe fn(isize) -> isize {square}`
    |
+   = help: the trait `for<'r> std::ops::Fn<(&'r isize,)>` is not implemented for `unsafe fn(isize) -> isize {square}`
 note: required by `call_it`
   --> $DIR/unboxed-closures-wrong-arg-type-extern-fn.rs:18:1
    |
 LL | fn call_it<F:Fn(&isize)->isize>(_: &F, _: isize) -> isize { 0 }
    | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
 
-error[E0277]: the trait bound `for<'r> unsafe fn(isize) -> isize {square}: std::ops::FnMut<(&'r isize,)>` is not satisfied
+error[E0277]: expected a `std::ops::FnMut<(&isize,)>` closure, found `unsafe fn(isize) -> isize {square}`
   --> $DIR/unboxed-closures-wrong-arg-type-extern-fn.rs:28:13
    |
 LL |     let y = call_it_mut(&mut square, 22);
-   |             ^^^^^^^^^^^ the trait `for<'r> std::ops::FnMut<(&'r isize,)>` is not implemented for `unsafe fn(isize) -> isize {square}`
+   |             ^^^^^^^^^^^ expected an `FnMut<(&isize,)>` closure, found `unsafe fn(isize) -> isize {square}`
    |
+   = help: the trait `for<'r> std::ops::FnMut<(&'r isize,)>` is not implemented for `unsafe fn(isize) -> isize {square}`
 note: required by `call_it_mut`
   --> $DIR/unboxed-closures-wrong-arg-type-extern-fn.rs:19:1
    |
 LL | fn call_it_mut<F:FnMut(&isize)->isize>(_: &mut F, _: isize) -> isize { 0 }
    | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
 
-error[E0277]: the trait bound `for<'r> unsafe fn(isize) -> isize {square}: std::ops::FnOnce<(&'r isize,)>` is not satisfied
+error[E0277]: expected a `std::ops::FnOnce<(&isize,)>` closure, found `unsafe fn(isize) -> isize {square}`
   --> $DIR/unboxed-closures-wrong-arg-type-extern-fn.rs:33:13
    |
 LL |     let z = call_it_once(square, 22);
-   |             ^^^^^^^^^^^^ the trait `for<'r> std::ops::FnOnce<(&'r isize,)>` is not implemented for `unsafe fn(isize) -> isize {square}`
+   |             ^^^^^^^^^^^^ expected an `FnOnce<(&isize,)>` closure, found `unsafe fn(isize) -> isize {square}`
    |
+   = help: the trait `for<'r> std::ops::FnOnce<(&'r isize,)>` is not implemented for `unsafe fn(isize) -> isize {square}`
 note: required by `call_it_once`
   --> $DIR/unboxed-closures-wrong-arg-type-extern-fn.rs:20:1
    |