Apply suggestions from code review

Co-authored-by: Paolo Tranquilli <redsun82@github.com>

Author: aibaars

rust/extractor/src/translate/base.rs

@@ -41,15 +41,20 @@ macro_rules! pre_emit {
     };
     ($($_:tt)*) => {};
 }
+
+// TODO: remove the mannually written Label conversions. These can be auto-generated by
+// changing the base class of AssocItem from AstNode to Item
 impl From<crate::trap::Label<generated::AssocItem>> for crate::trap::Label<generated::Item> {
     fn from(value: crate::trap::Label<generated::AssocItem>) -> Self {
-        // SAFETY: this is safe because in the dbscheme Item is a subclass of Stmt
+        // SAFETY: this is safe because every concrete instance of `@assoc_item` is also an instance of `@item`
         unsafe { Self::from_untyped(value.as_untyped()) }
     }
 }
+// TODO: remove the mannually written Label conversions. These can be auto-generated by
+// changing the base class of ExternItem from AstNode to Item
 impl From<crate::trap::Label<generated::ExternItem>> for crate::trap::Label<generated::Item> {
     fn from(value: crate::trap::Label<generated::ExternItem>) -> Self {
-        // SAFETY: this is safe because in the dbscheme Item is a subclass of Stmt
+        // SAFETY: this is safe because every concrete instance of `@extern_item` is also an instance of `@item`
         unsafe { Self::from_untyped(value.as_untyped()) }
     }
 }