Validate naked functions definitions

compiler/rustc_lint_defs/src/builtin.rs

@@ -2742,6 +2742,50 @@ declare_lint! {
     "detects deprecation attributes with no effect",
 }
 
+declare_lint! {
+    /// The `unsupported_naked_functions` lint detects naked function
+    /// definitions that are unsupported but were previously accepted.
+    ///
+    /// ### Example
+    ///
+    /// ```rust
+    /// #![feature(naked_functions)]
+    ///
+    /// #[naked]
+    /// pub fn f() -> u32 {
+    ///     42
+    /// }
+    /// ```
+    ///
+    /// {{produces}}
+    ///
+    /// ### Explanation
+    ///
+    /// The naked functions must be defined using a single inline assembly
+    /// block.
+    ///
+    /// The execution must never fall through past the end of the assembly
+    /// code so the block must use `noreturn` option. The asm block can also
+    /// use `att_syntax` option, but other options are not allowed.
+    ///
+    /// The asm block must not contain any operands other than `const` and
+    /// `sym`. Additionally, naked function should specify a non-Rust ABI.
+    ///
+    /// While other definitions of naked functions were previously accepted,
+    /// they are unsupported and might not work reliably. This is a
+    /// [future-incompatible] lint that will transition into hard error in
+    /// the future.
+    ///
+    /// [future-incompatible]: ../index.md#future-incompatible-lints
+    pub UNSUPPORTED_NAKED_FUNCTIONS,
+    Warn,
+    "unsupported naked function definitions",
+    @future_incompatible = FutureIncompatibleInfo {
+        reference: "issue #32408 <https://github.com/rust-lang/rust/issues/32408>",
+        edition: None,
+    };
+}
+
 declare_tool_lint! {
     pub rustc::INEFFECTIVE_UNSTABLE_TRAIT_IMPL,
     Deny,
@@ -2832,6 +2876,7 @@ declare_lint_pass! {
         UNINHABITED_STATIC,
         FUNCTION_ITEM_REFERENCES,
         USELESS_DEPRECATED,
+        UNSUPPORTED_NAKED_FUNCTIONS,
     ]
 }