Lint against named asm labels

compiler/rustc_lint_defs/src/builtin.rs

@@ -2470,6 +2470,38 @@ declare_lint! {
     "incorrect use of inline assembly",
 }
 
+declare_lint! {
+    /// The `named_asm_labels` lint detects the use of named labels in the
+    /// inline `asm!` macro.
+    ///
+    /// ### Example
+    ///
+    /// ```rust,compile_fail
+    /// fn main() {
+    ///     unsafe {
+    ///         asm!("foo: bar");
+    ///     }
+    /// }
+    /// ```
+    ///
+    /// {{produces}}
+    ///
+    /// ### Explanation
+    ///
+    /// LLVM's assembler is allowed to duplicate inline assembly blocks for any
+    /// reason, for example when it is in a function that gets inlined. Because
+    /// of this, GNU assembler [local labels] *must* be used instead of labels
+    /// with a name. Using named labels might cause assembler or linker errors.
+    ///
+    /// See the [unstable book] for more details.
+    ///
+    /// [local labels]: https://sourceware.org/binutils/docs/as/Symbol-Names.html#Local-Labels
+    /// [unstable book]: https://doc.rust-lang.org/nightly/unstable-book/library-features/asm.html#labels
+    pub NAMED_ASM_LABELS,
+    Deny,
+    "named labels in inline assembly",
+}
+
 declare_lint! {
     /// The `unsafe_op_in_unsafe_fn` lint detects unsafe operations in unsafe
     /// functions without an explicit unsafe block.

compiler/rustc_lint_defs/src/lib.rs

@@ -274,7 +274,7 @@ impl<HCX> ToStableHashKey<HCX> for LintId {
 }
 
 // Duplicated from rustc_session::config::ExternDepSpec to avoid cyclic dependency
-#[derive(PartialEq, Debug)]
+#[derive(PartialEq)]
 pub enum ExternDepSpec {
     Json(Json),
     Raw(String),
@@ -282,7 +282,7 @@ pub enum ExternDepSpec {
 
 // This could be a closure, but then implementing derive trait
 // becomes hacky (and it gets allocated).
-#[derive(PartialEq, Debug)]
+#[derive(PartialEq)]
 pub enum BuiltinLintDiagnostics {
     Normal,
     BareTraitObject(Span, /* is_global */ bool),
@@ -305,6 +305,7 @@ pub enum BuiltinLintDiagnostics {
     ReservedPrefix(Span),
     TrailingMacro(bool, Ident),
     BreakWithLabelAndLoop(Span),
+    NamedAsmLabel(String),
 }
 
 /// Lints that are buffered up early on in the `Session` before the