add a warning if the old-style of pos is written

calyx-frontend/src/attribute.rs

@@ -279,6 +279,11 @@ impl FromStr for Attribute {
             if DEPRECATED_ATTRIBUTES.contains(&s) {
                 log::warn!("The attribute @{s} is deprecated and will be ignored by the compiler.");
             }
+
+            if let Ok(SetAttribute::Set(_)) = SetAttribute::from_str(s) {
+                log::warn!("Set attribute {s} incorrectly written as a standard attribute, i.e. '@{s}(..)' or '\"{s}\" = ..'. This will be ignored by the compiler. Instead write '@{s}{{..}}' or '\"{s}\" = {{..}}'.");
+            }
+
             // Reject attributes that all caps since those are reserved for internal attributes
             if s.to_uppercase() == s {
                 return Err(Error::misc(format!("Invalid attribute: {}. All caps attributes are reserved for internal use.", s)));