Rollup merge of #95663 - notriddle:notriddle/unsafe-fn-closure, r=compiler-errors

diagnostics: give a special note for unsafe fn / Fn/FnOnce/FnMut

Fixes #90073

Author: Dylan-DPC

core/src/ops/function.rs

@@ -60,6 +60,12 @@
         Args = "()",
         note = "wrap the `{Self}` in a closure with no arguments: `|| {{ /* code */ }}`"
     ),
+    on(
+        _Self = "unsafe fn",
+        note = "unsafe function cannot be called generically without an unsafe block",
+        // SAFETY: tidy is not smart enough to tell that the below unsafe block is a string
+        label = "call the function in a closure: `|| unsafe {{ /* code */ }}`"
+    ),
     message = "expected a `{Fn}<{Args}>` closure, found `{Self}`",
     label = "expected an `Fn<{Args}>` closure, found `{Self}`"
 )]
@@ -141,6 +147,12 @@ pub trait Fn<Args>: FnMut<Args> {
         Args = "()",
         note = "wrap the `{Self}` in a closure with no arguments: `|| {{ /* code */ }}`"
     ),
+    on(
+        _Self = "unsafe fn",
+        note = "unsafe function cannot be called generically without an unsafe block",
+        // SAFETY: tidy is not smart enough to tell that the below unsafe block is a string
+        label = "call the function in a closure: `|| unsafe {{ /* code */ }}`"
+    ),
     message = "expected a `{FnMut}<{Args}>` closure, found `{Self}`",
     label = "expected an `FnMut<{Args}>` closure, found `{Self}`"
 )]
@@ -214,6 +226,12 @@ pub trait FnMut<Args>: FnOnce<Args> {
         Args = "()",
         note = "wrap the `{Self}` in a closure with no arguments: `|| {{ /* code */ }}`"
     ),
+    on(
+        _Self = "unsafe fn",
+        note = "unsafe function cannot be called generically without an unsafe block",
+        // SAFETY: tidy is not smart enough to tell that the below unsafe block is a string
+        label = "call the function in a closure: `|| unsafe {{ /* code */ }}`"
+    ),
     message = "expected a `{FnOnce}<{Args}>` closure, found `{Self}`",
     label = "expected an `FnOnce<{Args}>` closure, found `{Self}`"
 )]