add ERRORs notation in doc_unsafe.rs

Well, I mistakenly thinking it was the test file for [`undocumented_unsafe_blocks`] at first...
but it doesn't make things worse anyway, so I keep them lol.

Author: J-ZhengLi

tests/ui/doc_unsafe.rs

@@ -7,6 +7,7 @@ use proc_macros::external;
 
 /// This is not sufficiently documented
 pub unsafe fn destroy_the_planet() {
+    //~^ ERROR: unsafe function's docs miss `# Safety` section
     unimplemented!();
 }
 
@@ -30,6 +31,7 @@ mod private_mod {
     }
 
     pub unsafe fn republished() {
+        //~^ ERROR: unsafe function's docs miss `# Safety` section
         unimplemented!();
     }
 }
@@ -38,12 +40,14 @@ pub use private_mod::republished;
 
 pub trait SafeTraitUnsafeMethods {
     unsafe fn woefully_underdocumented(self);
+    //~^ ERROR: unsafe function's docs miss `# Safety` section
 
     /// # Safety
     unsafe fn at_least_somewhat_documented(self);
 }
 
 pub unsafe trait UnsafeTrait {
+    //~^ ERROR: docs for unsafe trait missing `# Safety` section
     fn method();
 }
 
@@ -74,6 +78,7 @@ unsafe impl DocumentedUnsafeTrait for Struct {
 
 impl Struct {
     pub unsafe fn more_undocumented_unsafe() -> Self {
+        //~^ ERROR: unsafe function's docs miss `# Safety` section
         unimplemented!();
     }
 
@@ -103,6 +108,7 @@ macro_rules! very_unsafe {
 }
 
 very_unsafe!();
+//~^ ERROR: unsafe function's docs miss `# Safety` section
 
 // we don't lint code from external macros
 external! {

tests/ui/doc_unsafe.stderr

@@ -8,31 +8,31 @@ LL | pub unsafe fn destroy_the_planet() {
    = help: to override `-D warnings` add `#[allow(clippy::missing_safety_doc)]`
 
 error: unsafe function's docs miss `# Safety` section
-  --> $DIR/doc_unsafe.rs:32:5
+  --> $DIR/doc_unsafe.rs:33:5
    |
 LL |     pub unsafe fn republished() {
    |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^
 
 error: unsafe function's docs miss `# Safety` section
-  --> $DIR/doc_unsafe.rs:40:5
+  --> $DIR/doc_unsafe.rs:42:5
    |
 LL |     unsafe fn woefully_underdocumented(self);
    |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
 
 error: docs for unsafe trait missing `# Safety` section
-  --> $DIR/doc_unsafe.rs:46:1
+  --> $DIR/doc_unsafe.rs:49:1
    |
 LL | pub unsafe trait UnsafeTrait {
    | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^
 
 error: unsafe function's docs miss `# Safety` section
-  --> $DIR/doc_unsafe.rs:76:5
+  --> $DIR/doc_unsafe.rs:80:5
    |
 LL |     pub unsafe fn more_undocumented_unsafe() -> Self {
    |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
 
 error: unsafe function's docs miss `# Safety` section
-  --> $DIR/doc_unsafe.rs:92:9
+  --> $DIR/doc_unsafe.rs:97:9
    |
 LL |         pub unsafe fn whee() {
    |         ^^^^^^^^^^^^^^^^^^^^