Port #[rustc_skip_during_method_dispatch] to the new attribute system

compiler/rustc_attr_parsing/src/parser.rs

@@ -169,9 +169,15 @@ impl<'a> ArgParser<'a> {
         }
     }
 
-    /// Asserts that there are no arguments
-    pub fn no_args(&self) -> bool {
-        matches!(self, Self::NoArgs)
+    /// Assert that there were no args.
+    /// If there were, get a span to the arguments
+    /// (to pass to [`AcceptContext::expected_no_args`](crate::context::AcceptContext::expected_no_args)).
+    pub fn no_args(&self) -> Result<(), Span> {
+        match self {
+            Self::NoArgs => Ok(()),
+            Self::List(args) => Err(args.span),
+            Self::NameValue(args) => Err(args.eq_span.to(args.value_span)),
+        }
     }
 }