Forbid asm unwind to work with labels

compiler/rustc_builtin_macros/src/asm.rs

@@ -245,6 +245,7 @@ pub fn parse_asm_args<'a>(
     let mut have_real_output = false;
     let mut outputs_sp = vec![];
     let mut regclass_outputs = vec![];
+    let mut labels_sp = vec![];
     for (op, op_sp) in &args.operands {
         match op {
             ast::InlineAsmOperand::Out { reg, expr, .. }
@@ -262,6 +263,9 @@ pub fn parse_asm_args<'a>(
                     regclass_outputs.push(*op_sp);
                 }
             }
+            ast::InlineAsmOperand::Label { .. } => {
+                labels_sp.push(*op_sp);
+            }
             _ => {}
         }
     }
@@ -273,6 +277,9 @@ pub fn parse_asm_args<'a>(
         // Bail out now since this is likely to confuse MIR
         return Err(err);
     }
+    if args.options.contains(ast::InlineAsmOptions::MAY_UNWIND) && !labels_sp.is_empty() {
+        dcx.emit_err(errors::AsmMayUnwind { labels_sp });
+    }
 
     if args.clobber_abis.len() > 0 {
         if is_global_asm {