Move closure-to-extern-fn-ptr-coercion tests into ui

src/test/compile-fail/coerce-unsafe-closure-to-unsafe-fn-ptr.rs

@@ -1,8 +1,5 @@
 fn main() {
     let _: unsafe fn() = || { ::std::pin::Pin::new_unchecked(&0_u8); };
     //~^ ERROR E0133
-    let _: unsafe extern "C" fn() = || { ::std::pin::Pin::new_unchecked(&0_u8); };
-    //~^ ERROR E0133
     let _: unsafe fn() = || unsafe { ::std::pin::Pin::new_unchecked(&0_u8); }; // OK
-    let _: unsafe extern "C" fn() = || unsafe { ::std::pin::Pin::new_unchecked(&0_u8); }; // OK
 }

src/test/ui/closure-to-extern-fn-ptr-coercion/coerce-closure-to-extern-c-fn-ptr.rs

@@ -0,0 +1,16 @@
+// compile-pass
+
+fn call_extern_c(func: extern "C" fn()) {
+    func()
+}
+
+unsafe fn call_unsafe_extern_c(func: unsafe extern "C" fn()) {
+    func()
+}
+
+pub fn main() {
+    call_extern_c(|| {});
+    unsafe {
+        call_unsafe_extern_c(|| {});
+    }
+}

src/test/ui/closure-to-extern-fn-ptr-coercion/coerce-unsafe-closure-to-unsafe-extern-fn-ptr.rs

@@ -0,0 +1,4 @@
+fn main() {
+    let _: unsafe extern "C" fn() = || { ::std::pin::Pin::new_unchecked(&0_u8); }; //~ ERROR E0133
+    let _: unsafe extern "C" fn() = || unsafe { ::std::pin::Pin::new_unchecked(&0_u8); }; // OK
+}

src/test/ui/closure-to-extern-fn-ptr-coercion/coerce-unsafe-closure-to-unsafe-extern-fn-ptr.stderr

@@ -0,0 +1,11 @@
+error[E0133]: call to unsafe function is unsafe and requires unsafe function or block
+  --> $DIR/coerce-unsafe-closure-to-unsafe-extern-fn-ptr.rs:2:42
+   |
+LL |     let _: unsafe extern "C" fn() = || { ::std::pin::Pin::new_unchecked(&0_u8); };
+   |                                          ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ call to unsafe function
+   |
+   = note: consult the function's documentation for information on how to avoid undefined behavior
+
+error: aborting due to previous error
+
+For more information about this error, try `rustc --explain E0133`.