Lint unnecessary safety comments

CHANGELOG.md

@@ -4451,6 +4451,7 @@ Released 2018-09-13
 [`unnecessary_mut_passed`]: https://rust-lang.github.io/rust-clippy/master/index.html#unnecessary_mut_passed
 [`unnecessary_operation`]: https://rust-lang.github.io/rust-clippy/master/index.html#unnecessary_operation
 [`unnecessary_owned_empty_strings`]: https://rust-lang.github.io/rust-clippy/master/index.html#unnecessary_owned_empty_strings
+[`unnecessary_safety_comment`]: https://rust-lang.github.io/rust-clippy/master/index.html#unnecessary_safety_comment
 [`unnecessary_safety_doc`]: https://rust-lang.github.io/rust-clippy/master/index.html#unnecessary_safety_doc
 [`unnecessary_self_imports`]: https://rust-lang.github.io/rust-clippy/master/index.html#unnecessary_self_imports
 [`unnecessary_sort_by`]: https://rust-lang.github.io/rust-clippy/master/index.html#unnecessary_sort_by

clippy_lints/src/declared_lints.rs

@@ -584,6 +584,7 @@ pub(crate) static LINTS: &[&crate::LintInfo] = &[
     crate::types::TYPE_COMPLEXITY_INFO,
     crate::types::VEC_BOX_INFO,
     crate::undocumented_unsafe_blocks::UNDOCUMENTED_UNSAFE_BLOCKS_INFO,
+    crate::undocumented_unsafe_blocks::UNNECESSARY_SAFETY_COMMENT_INFO,
     crate::unicode::INVISIBLE_CHARACTERS_INFO,
     crate::unicode::NON_ASCII_LITERAL_INFO,
     crate::unicode::UNICODE_NOT_NFC_INFO,

clippy_utils/src/visitors.rs

@@ -170,36 +170,36 @@ where
         cb: F,
     }
 
-    struct WithStmtGuarg<'a, F> {
+    struct WithStmtGuard<'a, F> {
         val: &'a mut RetFinder<F>,
         prev_in_stmt: bool,
     }
 
     impl<F> RetFinder<F> {
-        fn inside_stmt(&mut self, in_stmt: bool) -> WithStmtGuarg<'_, F> {
+        fn inside_stmt(&mut self, in_stmt: bool) -> WithStmtGuard<'_, F> {
             let prev_in_stmt = std::mem::replace(&mut self.in_stmt, in_stmt);
-            WithStmtGuarg {
+            WithStmtGuard {
                 val: self,
                 prev_in_stmt,
             }
         }
     }
 
-    impl<F> std::ops::Deref for WithStmtGuarg<'_, F> {
+    impl<F> std::ops::Deref for WithStmtGuard<'_, F> {
         type Target = RetFinder<F>;
 
         fn deref(&self) -> &Self::Target {
             self.val
         }
     }
 
-    impl<F> std::ops::DerefMut for WithStmtGuarg<'_, F> {
+    impl<F> std::ops::DerefMut for WithStmtGuard<'_, F> {
         fn deref_mut(&mut self) -> &mut Self::Target {
             self.val
         }
     }
 
-    impl<F> Drop for WithStmtGuarg<'_, F> {
+    impl<F> Drop for WithStmtGuard<'_, F> {
         fn drop(&mut self) {
             self.val.in_stmt = self.prev_in_stmt;
         }

tests/ui/undocumented_unsafe_blocks.rs

@@ -1,6 +1,6 @@
 // aux-build:proc_macro_unsafe.rs
 
-#![warn(clippy::undocumented_unsafe_blocks)]
+#![warn(clippy::undocumented_unsafe_blocks, clippy::unnecessary_safety_comment)]
 #![allow(clippy::let_unit_value, clippy::missing_safety_doc)]
 
 extern crate proc_macro_unsafe;

tests/ui/undocumented_unsafe_blocks.stderr

@@ -239,6 +239,19 @@ LL |     unsafe impl TrailingComment for () {} // SAFETY:
    |
    = help: consider adding a safety comment on the preceding line
 
+error: constant item has unnecessary safety comment
+  --> $DIR/undocumented_unsafe_blocks.rs:471:5
+   |
+LL |     const BIG_NUMBER: i32 = 1000000;
+   |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+   |
+help: consider removing the safety comment
+  --> $DIR/undocumented_unsafe_blocks.rs:470:5
+   |
+LL |     // SAFETY:
+   |     ^^^^^^^^^^
+   = note: `-D clippy::unnecessary-safety-comment` implied by `-D warnings`
+
 error: unsafe impl missing a safety comment
   --> $DIR/undocumented_unsafe_blocks.rs:472:5
    |
@@ -271,6 +284,24 @@ LL |         unsafe {};
    |
    = help: consider adding a safety comment on the preceding line
 
+error: statement has unnecessary safety comment
+  --> $DIR/undocumented_unsafe_blocks.rs:501:5
+   |
+LL | /     let _ = {
+LL | |         if unsafe { true } {
+LL | |             todo!();
+LL | |         } else {
+...  |
+LL | |         }
+LL | |     };
+   | |______^
+   |
+help: consider removing the safety comment
+  --> $DIR/undocumented_unsafe_blocks.rs:500:5
+   |
+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:502:12
    |
@@ -287,5 +318,5 @@ LL |             let bar = unsafe {};
    |
    = help: consider adding a safety comment on the preceding line
 
-error: aborting due to 34 previous errors
+error: aborting due to 36 previous errors
 

tests/ui/unnecessary_safety_comment.rs

@@ -0,0 +1,51 @@
+#![warn(clippy::undocumented_unsafe_blocks, clippy::unnecessary_safety_comment)]
+#![allow(clippy::let_unit_value, clippy::missing_safety_doc)]
+
+mod unsafe_items_invalid_comment {
+    // SAFETY:
+    const CONST: u32 = 0;
+    // SAFETY:
+    static STATIC: u32 = 0;
+    // SAFETY:
+    struct Struct;
+    // SAFETY:
+    enum Enum {}
+    // SAFETY:
+    mod module {}
+}
+
+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
+    if num > 24 {}
+
+    // SAFETY: unnecessary
+    24
+}
+
+fn main() {}

tests/ui/unnecessary_safety_comment.stderr

@@ -0,0 +1,115 @@
+error: constant item has unnecessary safety comment
+  --> $DIR/unnecessary_safety_comment.rs:6:5
+   |
+LL |     const CONST: u32 = 0;
+   |     ^^^^^^^^^^^^^^^^^^^^^
+   |
+help: consider removing the safety comment
+  --> $DIR/unnecessary_safety_comment.rs:5:5
+   |
+LL |     // SAFETY:
+   |     ^^^^^^^^^^
+   = note: `-D clippy::unnecessary-safety-comment` implied by `-D warnings`
+
+error: static item has unnecessary safety comment
+  --> $DIR/unnecessary_safety_comment.rs:8:5
+   |
+LL |     static STATIC: u32 = 0;
+   |     ^^^^^^^^^^^^^^^^^^^^^^^
+   |
+help: consider removing the safety comment
+  --> $DIR/unnecessary_safety_comment.rs:7:5
+   |
+LL |     // SAFETY:
+   |     ^^^^^^^^^^
+
+error: struct has unnecessary safety comment
+  --> $DIR/unnecessary_safety_comment.rs:10:5
+   |
+LL |     struct Struct;
+   |     ^^^^^^^^^^^^^^
+   |
+help: consider removing the safety comment
+  --> $DIR/unnecessary_safety_comment.rs:9:5
+   |
+LL |     // SAFETY:
+   |     ^^^^^^^^^^
+
+error: enum has unnecessary safety comment
+  --> $DIR/unnecessary_safety_comment.rs:12:5
+   |
+LL |     enum Enum {}
+   |     ^^^^^^^^^^^^
+   |
+help: consider removing the safety comment
+  --> $DIR/unnecessary_safety_comment.rs:11:5
+   |
+LL |     // SAFETY:
+   |     ^^^^^^^^^^
+
+error: module has unnecessary safety comment
+  --> $DIR/unnecessary_safety_comment.rs:14:5
+   |
+LL |     mod module {}
+   |     ^^^^^^^^^^^^^
+   |
+help: consider removing the safety comment
+  --> $DIR/unnecessary_safety_comment.rs:13:5
+   |
+LL |     // SAFETY:
+   |     ^^^^^^^^^^
+
+error: impl has unnecessary safety comment
+  --> $DIR/unnecessary_safety_comment.rs:33:13
+   |
+LL |             impl T for $t {}
+   |             ^^^^^^^^^^^^^^^^
+...
+LL |     with_safety_comment!(i32);
+   |     ------------------------- in this macro invocation
+   |
+help: consider removing the safety comment
+  --> $DIR/unnecessary_safety_comment.rs:32:13
+   |
+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/unnecessary_safety_comment.rs:48:5
+   |
+LL |     24
+   |     ^^
+   |
+help: consider removing the safety comment
+  --> $DIR/unnecessary_safety_comment.rs:47:5
+   |
+LL |     // SAFETY: unnecessary
+   |     ^^^^^^^^^^^^^^^^^^^^^^
+
+error: statement has unnecessary safety comment
+  --> $DIR/unnecessary_safety_comment.rs:42:5
+   |
+LL |     let num = 42;
+   |     ^^^^^^^^^^^^^
+   |
+help: consider removing the safety comment
+  --> $DIR/unnecessary_safety_comment.rs:41:5
+   |
+LL |     // SAFETY: unnecessary
+   |     ^^^^^^^^^^^^^^^^^^^^^^
+
+error: statement has unnecessary safety comment
+  --> $DIR/unnecessary_safety_comment.rs:45:5
+   |
+LL |     if num > 24 {}
+   |     ^^^^^^^^^^^^^^
+   |
+help: consider removing the safety comment
+  --> $DIR/unnecessary_safety_comment.rs:44:5
+   |
+LL |     // SAFETY: unnecessary
+   |     ^^^^^^^^^^^^^^^^^^^^^^
+
+error: aborting due to 9 previous errors
+