2 files changed, 12 insertions, 9 deletions
diff --git a/src/test/ui/proc-macro/signature.rs b/src/test/ui/proc-macro/signature.rs
index e08928716b0..2302238253e 100644
--- a/src/test/ui/proc-macro/signature.rs
+++ b/src/test/ui/proc-macro/signature.rs
@@ -8,6 +8,6 @@ extern crate proc_macro;
 
 #[proc_macro_derive(A)]
 pub unsafe extern "C" fn foo(a: i32, b: u32) -> u32 {
-    //~^ ERROR: mismatched types
+    //~^ ERROR: expected a `Fn<(proc_macro::TokenStream,)>` closure, found `unsafe extern "C" fn
     loop {}
 }
diff --git a/src/test/ui/proc-macro/signature.stderr b/src/test/ui/proc-macro/signature.stderr
index 262a64acc54..78b0beff0da 100644
--- a/src/test/ui/proc-macro/signature.stderr
+++ b/src/test/ui/proc-macro/signature.stderr
@@ -1,20 +1,23 @@
-error[E0308]: mismatched types
+error[E0277]: expected a `Fn<(proc_macro::TokenStream,)>` closure, found `unsafe extern "C" fn(i32, u32) -> u32 {foo}`
   --> $DIR/signature.rs:10:1
    |
 LL | / pub unsafe extern "C" fn foo(a: i32, b: u32) -> u32 {
 LL | |
 LL | |     loop {}
 LL | | }
-   | |_^ expected normal fn, found unsafe fn
+   | | ^
+   | | |
+   | |_call the function in a closure: `|| unsafe { /* code */ }`
+   |   required by a bound introduced by this call
    |
-   = note: expected fn pointer `fn(proc_macro::TokenStream) -> proc_macro::TokenStream`
-                 found fn item `unsafe extern "C" fn(i32, u32) -> u32 {foo}`
-note: associated function defined here
+   = help: the trait `Fn<(proc_macro::TokenStream,)>` is not implemented for `unsafe extern "C" fn(i32, u32) -> u32 {foo}`
+   = note: unsafe function cannot be called generically without an unsafe block
+note: required by a bound in `ProcMacro::custom_derive`
   --> $SRC_DIR/proc_macro/src/bridge/client.rs:LL:COL
    |
-LL |     pub const fn custom_derive(
-   |                  ^^^^^^^^^^^^^
+LL |         expand: impl Fn(crate::TokenStream) -> crate::TokenStream + Copy,
+   |                      ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ required by this bound in `ProcMacro::custom_derive`
 
 error: aborting due to previous error
 
-For more information about this error, try `rustc --explain E0308`.
+For more information about this error, try `rustc --explain E0277`.