seal PrimType trait

src/types/simple.rs

@@ -91,14 +91,22 @@ impl TypeTag {
 }
 
 /// Trait of primitive types (SimpleType or ClassicType).
-pub trait PrimType: std::fmt::Debug + Clone + 'static {
+pub trait PrimType: private::Sealed + std::fmt::Debug + Clone + 'static {
  // may be updated with functions in future for necessary shared functionality
  // across ClassicType, SimpleType and HashableType.
  // Currently used to constrain Container<T>
  /// Tells us the [TypeTag] of the type represented by the receiver.
  fn tag(&self) -> TypeTag;
 }
 
+// sealed trait pattern to prevent users extending PrimType
+mod private {
+ use super::{ClassicType, HashableType, SimpleType};
+ pub trait Sealed {}
+ impl Sealed for SimpleType {}
+ impl Sealed for ClassicType {}
+ impl Sealed for HashableType {}
+}
 /// A type that represents a container of other types.
 ///
 /// For algebraic types Sum, Tuple if one element of type row is linear, the

src/types/simple/serialize.rs

@@ -67,6 +67,7 @@ pub(crate) enum SerSimpleType {
  },
 }
 
+impl super::private::Sealed for SerSimpleType {}
 impl PrimType for SerSimpleType {
  fn tag(&self) -> TypeTag {
  unimplemented!()