Implement elided_named_lifetimes lint

compiler/rustc_lint_defs/src/builtin.rs

@@ -42,6 +42,7 @@ declare_lint_pass! {
         DUPLICATE_MACRO_ATTRIBUTES,
         ELIDED_LIFETIMES_IN_ASSOCIATED_CONSTANT,
         ELIDED_LIFETIMES_IN_PATHS,
+        ELIDED_NAMED_LIFETIMES,
         EXPLICIT_BUILTIN_CFGS_IN_FLAGS,
         EXPORTED_PRIVATE_DEPENDENCIES,
         FFI_UNWIND_CALLS,
@@ -1862,6 +1863,38 @@ declare_lint! {
     "hidden lifetime parameters in types are deprecated"
 }
 
+declare_lint! {
+    /// The `elided_named_lifetimes` lint detects when an elided
+    /// lifetime ends up being a named lifetime, such as `'static`
+    /// or some lifetime parameter `'a`.
+    ///
+    /// ### Example
+    ///
+    /// ```rust,compile_fail
+    /// #![deny(elided_named_lifetimes)]
+    /// struct Foo;
+    /// impl Foo {
+    ///     pub fn get_mut(&'static self, x: &mut u8) -> &mut u8 {
+    ///         unsafe { &mut *(x as *mut _) }
+    ///     }
+    /// }
+    /// ```
+    ///
+    /// {{produces}}
+    ///
+    /// ### Explanation
+    ///
+    /// Lifetime elision is quite useful, because it frees you from having
+    /// to give each lifetime its own name, but sometimes it can produce
+    /// somewhat surprising resolutions. In safe code, it is mostly okay,
+    /// because the borrow checker prevents any unsoundness, so the worst
+    /// case scenario is you get a confusing error message in some other place.
+    /// But with `unsafe` code, such unexpected resolutions may lead to unsound code.
+    pub ELIDED_NAMED_LIFETIMES,
+    Warn,
+    "detects when an elided lifetime gets resolved to be `'static` or some named parameter"
+}
+
 declare_lint! {
     /// The `bare_trait_objects` lint suggests using `dyn Trait` for trait
     /// objects.