Disable unused variable lint for naked functions

compiler/rustc_passes/src/liveness.rs

@@ -332,6 +332,11 @@ impl<'tcx> Visitor<'tcx> for IrMaps<'tcx> {
             }
         }
 
+        // Don't run unused pass for #[naked]
+        if self.tcx.has_attr(def_id, sym::naked) {
+            return;
+        }
+
         if let Some(captures) = maps.tcx.typeck(local_def_id).closure_min_captures.get(&def_id) {
             for &var_hir_id in captures.keys() {
                 let var_name = maps.tcx.hir().name(var_hir_id);

src/test/ui/asm/naked-functions-unused.rs

@@ -0,0 +1,81 @@
+// only-x86_64
+#![deny(unused)]
+#![feature(asm)]
+#![feature(naked_functions)]
+#![crate_type = "lib"]
+
+pub trait Trait {
+    extern "sysv64" fn trait_associated(a: usize, b: usize) -> usize;
+    extern "sysv64" fn trait_method(&self, a: usize, b: usize) -> usize;
+}
+
+pub mod normal {
+    pub extern "sysv64" fn function(a: usize, b: usize) -> usize {
+        //~^ ERROR unused variable: `a`
+        //~| ERROR unused variable: `b`
+        unsafe { asm!("", options(noreturn)); }
+    }
+
+    pub struct Normal;
+
+    impl Normal {
+        pub extern "sysv64" fn associated(a: usize, b: usize) -> usize {
+            //~^ ERROR unused variable: `a`
+            //~| ERROR unused variable: `b`
+            unsafe { asm!("", options(noreturn)); }
+        }
+
+        pub extern "sysv64" fn method(&self, a: usize, b: usize) -> usize {
+            //~^ ERROR unused variable: `a`
+            //~| ERROR unused variable: `b`
+            unsafe { asm!("", options(noreturn)); }
+        }
+    }
+
+    impl super::Trait for Normal {
+        extern "sysv64" fn trait_associated(a: usize, b: usize) -> usize {
+            //~^ ERROR unused variable: `a`
+            //~| ERROR unused variable: `b`
+            unsafe { asm!("", options(noreturn)); }
+        }
+
+        extern "sysv64" fn trait_method(&self, a: usize, b: usize) -> usize {
+            //~^ ERROR unused variable: `a`
+            //~| ERROR unused variable: `b`
+            unsafe { asm!("", options(noreturn)); }
+        }
+    }
+}
+
+pub mod naked {
+    #[naked]
+    pub extern "sysv64" fn function(a: usize, b: usize) -> usize {
+        unsafe { asm!("", options(noreturn)); }
+    }
+
+    pub struct Naked;
+
+    impl Naked {
+        #[naked]
+        pub extern "sysv64" fn associated(a: usize, b: usize) -> usize {
+            unsafe { asm!("", options(noreturn)); }
+        }
+
+        #[naked]
+        pub extern "sysv64" fn method(&self, a: usize, b: usize) -> usize {
+            unsafe { asm!("", options(noreturn)); }
+        }
+    }
+
+    impl super::Trait for Naked {
+        #[naked]
+        extern "sysv64" fn trait_associated(a: usize, b: usize) -> usize {
+            unsafe { asm!("", options(noreturn)); }
+        }
+
+        #[naked]
+        extern "sysv64" fn trait_method(&self, a: usize, b: usize) -> usize {
+            unsafe { asm!("", options(noreturn)); }
+        }
+    }
+}

src/test/ui/asm/naked-functions-unused.stderr

@@ -0,0 +1,69 @@
+error: unused variable: `a`
+  --> $DIR/naked-functions-unused.rs:13:37
+   |
+LL |     pub extern "sysv64" fn function(a: usize, b: usize) -> usize {
+   |                                     ^ help: if this is intentional, prefix it with an underscore: `_a`
+   |
+note: the lint level is defined here
+  --> $DIR/naked-functions-unused.rs:2:9
+   |
+LL | #![deny(unused)]
+   |         ^^^^^^
+   = note: `#[deny(unused_variables)]` implied by `#[deny(unused)]`
+
+error: unused variable: `b`
+  --> $DIR/naked-functions-unused.rs:13:47
+   |
+LL |     pub extern "sysv64" fn function(a: usize, b: usize) -> usize {
+   |                                               ^ help: if this is intentional, prefix it with an underscore: `_b`
+
+error: unused variable: `a`
+  --> $DIR/naked-functions-unused.rs:22:43
+   |
+LL |         pub extern "sysv64" fn associated(a: usize, b: usize) -> usize {
+   |                                           ^ help: if this is intentional, prefix it with an underscore: `_a`
+
+error: unused variable: `b`
+  --> $DIR/naked-functions-unused.rs:22:53
+   |
+LL |         pub extern "sysv64" fn associated(a: usize, b: usize) -> usize {
+   |                                                     ^ help: if this is intentional, prefix it with an underscore: `_b`
+
+error: unused variable: `a`
+  --> $DIR/naked-functions-unused.rs:28:46
+   |
+LL |         pub extern "sysv64" fn method(&self, a: usize, b: usize) -> usize {
+   |                                              ^ help: if this is intentional, prefix it with an underscore: `_a`
+
+error: unused variable: `b`
+  --> $DIR/naked-functions-unused.rs:28:56
+   |
+LL |         pub extern "sysv64" fn method(&self, a: usize, b: usize) -> usize {
+   |                                                        ^ help: if this is intentional, prefix it with an underscore: `_b`
+
+error: unused variable: `a`
+  --> $DIR/naked-functions-unused.rs:36:45
+   |
+LL |         extern "sysv64" fn trait_associated(a: usize, b: usize) -> usize {
+   |                                             ^ help: if this is intentional, prefix it with an underscore: `_a`
+
+error: unused variable: `b`
+  --> $DIR/naked-functions-unused.rs:36:55
+   |
+LL |         extern "sysv64" fn trait_associated(a: usize, b: usize) -> usize {
+   |                                                       ^ help: if this is intentional, prefix it with an underscore: `_b`
+
+error: unused variable: `a`
+  --> $DIR/naked-functions-unused.rs:42:48
+   |
+LL |         extern "sysv64" fn trait_method(&self, a: usize, b: usize) -> usize {
+   |                                                ^ help: if this is intentional, prefix it with an underscore: `_a`
+
+error: unused variable: `b`
+  --> $DIR/naked-functions-unused.rs:42:58
+   |
+LL |         extern "sysv64" fn trait_method(&self, a: usize, b: usize) -> usize {
+   |                                                          ^ help: if this is intentional, prefix it with an underscore: `_b`
+
+error: aborting due to 10 previous errors
+