Writing Semantic Checks with TypePal

I am trying to write semantic checks for my for my model using TypePal. Here is my model

Property(b => b.name)
      .ColumnOrder(3)
      .ColumnName("Name")
      .ColumnType(varchar(45))
      .ColumnType(date)
;

syntax Property
  = property: "Property" "(" Expr e ")" PropertyType*
;

syntax PropertyType
  = columnName: "." "ColumnName" "(" Expr e ")"
  | columnOrder: "." "ColumnOrder" "(" Expr e ")"
  | columnType: "." "ColumnType" "(" ColumnType c ")"
;

syntax ColumnType
  = intColumn: "int" 
  | varcharColumn: "varchar" "(" Expr e ")"
  | dateColumn: "date" 
;

How do I write a rule with TypePal that enforces the requirement that a given PropertyType can not be repeated. I want each PropertyType to be used at most once. In the example above ColumnType was used twice I want this flagged as a semantic error.

here is what I came up with.

 map[str, int] m = ();

    for (PropertyType pt <- p){
        switch(pt){
            case (PropertyType) `. ColumnType ( <ColumnType _>)` : {
              if ("ColumnType" notin m){
                 m = m + ("ColumnType" : 1);
              }
              else{
               c.report(error(p, "Duplicate occurrence of %v", "ColumnType"));
              }
            }
            case (PropertyType) `. ColumnName ( <Expr _>)` : {
               if ("ColumnName" notin m){
                 m = m + ("ColumnName" : 1);
               }
               else{
                 c.report(error(p, "Duplicate occurrence of %v", "ColumnName"));
              }
            }
            default : {
              if ("ColumnOrder" notin m){
                m = m + ("ColumnOrder" : 1);
              }
              else{
                c.report(error(p, "Duplicate occurrence of %v", "ColumnOrder"));
              }
            }
        }
    }