public BoundScope(BoundScope parent)
 {
     Parent = parent;
 }
 public BoundScope(BoundScope parent, string name)
 {
     Parent = parent;
     Name   = name;
 }
 public BoundBlockStatement(ImmutableArray <BoundStatement> statements, BoundScope scope = null)
 {
     Statements = statements;
     Scope      = scope;
 }