chore: addressing more PR comments

Author: benbellick

core/src/main/java/io/substrait/expression/proto/ProtoExpressionConverter.java

@@ -497,25 +497,21 @@ public Expression.Literal from(io.substrait.proto.Expression.Literal literal) {
               lookup.getType(userDefinedLiteral.getTypeReference(), extensions);
           String urn = type.urn();
           String name = type.name();
+          List<io.substrait.type.Type.Parameter> typeParameters =
+              userDefinedLiteral.getTypeParametersList().stream()
+                  .map(protoTypeConverter::from)
+                  .collect(Collectors.toList());
 
           switch (userDefinedLiteral.getValCase()) {
             case VALUE:
               return ExpressionCreator.userDefinedLiteralAny(
-                  literal.getNullable(),
-                  urn,
-                  name,
-                  userDefinedLiteral.getTypeParametersList().stream()
-                      .map(protoTypeConverter::from)
-                      .collect(Collectors.toList()),
-                  userDefinedLiteral.getValue());
+                  literal.getNullable(), urn, name, typeParameters, userDefinedLiteral.getValue());
             case STRUCT:
               return ExpressionCreator.userDefinedLiteralStruct(
                   literal.getNullable(),
                   urn,
                   name,
-                  userDefinedLiteral.getTypeParametersList().stream()
-                      .map(protoTypeConverter::from)
-                      .collect(Collectors.toList()),
+                  typeParameters,
                   userDefinedLiteral.getStruct().getFieldsList().stream()
                       .map(this::from)
                       .collect(Collectors.toList()));

core/src/main/java/io/substrait/type/Type.java

@@ -400,11 +400,11 @@ abstract class UserDefined implements Type {
      * vector<i32>} or custom types like {@code FixedArray<100>}. Each parameter in the list can be
      * either a type (like {@code i32}) or a value (like the integer {@code 100}).
      *
-     * <p>Unlike built-in parameterized types ({@link Map}, {@link ListType}, {@link Decimal}),
-     * which have fixed, known schemas with concrete typed fields, user-defined types have variable,
-     * unknown schemas. This is why UserDefined uses a generic {@link Parameter} list that can hold
-     * any mix of types or values, while other parameterized types use concrete fields like {@code
-     * Type key()} or {@code int precision()}.
+     * <p>Unlike built-in parameterized types ({@link Type.Map}, {@link Type.ListType}, {@link
+     * Type.Decimal}), which have fixed, known schemas with concrete typed fields, user-defined
+     * types have variable, unknown schemas. This is why UserDefined uses a generic {@link
+     * Parameter} list that can hold any mix of types or values, while other parameterized types use
+     * concrete fields like {@code Type key()} or {@code int precision()}.
      *
      * <p>For example, a user-defined {@code vector} type parameterized by {@code i32} would have
      * one type parameter containing the {@code i32} type definition, while a {@code FixedArray}