Lint unnecessary safety comments on statements and block tail expressions

2 files changed, 90 insertions, 1 deletions

diff --git a/tests/ui/undocumented_unsafe_blocks.rs b/tests/ui/undocumented_unsafe_blocks.rs
index f68e0b4915e..cb99ce0d421 100644
--- a/tests/ui/undocumented_unsafe_blocks.rs
+++ b/tests/ui/undocumented_unsafe_blocks.rs
@@ -522,4 +522,35 @@ fn issue_9142() {
     };
 }
 
+mod unnecessary_from_macro {
+    trait T {}
+
+    macro_rules! no_safety_comment {
+        ($t:ty) => {
+            impl T for $t {}
+        };
+    }
+
+    // FIXME: This is not caught
+    // Safety: unnecessary
+    no_safety_comment!(());
+
+    macro_rules! with_safety_comment {
+        ($t:ty) => {
+            // Safety: unnecessary
+            impl T for $t {}
+        };
+    }
+
+    with_safety_comment!(i32);
+}
+
+fn unnecessary_on_stmt_and_expr() -> u32 {
+    // SAFETY: unnecessary
+    let num = 42;
+
+    // SAFETY: unnecessary
+    24
+}
+
 fn main() {}
diff --git a/tests/ui/undocumented_unsafe_blocks.stderr b/tests/ui/undocumented_unsafe_blocks.stderr
index becad4f61a9..919fd51351c 100644
--- a/tests/ui/undocumented_unsafe_blocks.stderr
+++ b/tests/ui/undocumented_unsafe_blocks.stderr
@@ -344,6 +344,24 @@ LL |         unsafe {};
    |
    = help: consider adding a safety comment on the preceding line
 
+error: statement has unnecessary safety comment
+  --> $DIR/undocumented_unsafe_blocks.rs:514:5
+   |
+LL | /     let _ = {
+LL | |         if unsafe { true } {
+LL | |             todo!();
+LL | |         } else {
+...  |
+LL | |         }
+LL | |     };
+   | |______^
+   |
+help: consider removing the safety comment
+  --> $DIR/undocumented_unsafe_blocks.rs:513:5
+   |
+LL |     // SAFETY: this is more than one level away, so it should warn
+   |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+
 error: unsafe block missing a safety comment
   --> $DIR/undocumented_unsafe_blocks.rs:515:12
    |
@@ -360,5 +378,45 @@ LL |             let bar = unsafe {};
    |
    = help: consider adding a safety comment on the preceding line
 
-error: aborting due to 40 previous errors
+error: impl has unnecessary safety comment
+  --> $DIR/undocumented_unsafe_blocks.rs:541:13
+   |
+LL |             impl T for $t {}
+   |             ^^^^^^^^^^^^^^^^
+...
+LL |     with_safety_comment!(i32);
+   |     ------------------------- in this macro invocation
+   |
+help: consider removing the safety comment
+  --> $DIR/undocumented_unsafe_blocks.rs:540:13
+   |
+LL |             // Safety: unnecessary
+   |             ^^^^^^^^^^^^^^^^^^^^^^
+   = note: this error originates in the macro `with_safety_comment` (in Nightly builds, run with -Z macro-backtrace for more info)
+
+error: expression has unnecessary safety comment
+  --> $DIR/undocumented_unsafe_blocks.rs:553:5
+   |
+LL |     24
+   |     ^^
+   |
+help: consider removing the safety comment
+  --> $DIR/undocumented_unsafe_blocks.rs:552:5
+   |
+LL |     // SAFETY: unnecessary
+   |     ^^^^^^^^^^^^^^^^^^^^^^
+
+error: statement has unnecessary safety comment
+  --> $DIR/undocumented_unsafe_blocks.rs:550:5
+   |
+LL |     let num = 42;
+   |     ^^^^^^^^^^^^^
+   |
+help: consider removing the safety comment
+  --> $DIR/undocumented_unsafe_blocks.rs:549:5
+   |
+LL |     // SAFETY: unnecessary
+   |     ^^^^^^^^^^^^^^^^^^^^^^
+
+error: aborting due to 44 previous errors