anchor.diff:                  match m with
                       | SynModuleDecl.Let(_,bs,_) -> Some(List.map AstNode.Binding bs)
                       | SynModuleDecl.DoExpr(_,e,_) -> Some([AstNode.Expression e])
  +                    | SynModuleDecl.Open(_,_) -> None
                       | _ -> raise (new NotImplementedException("Add a new entry to pattern for ModuleDeclaration: " + (string m)))
               | Binding(b) ->
                   match b with
  
positive.code:                     | SynPat.Paren(p,_) -> Some([AstNode.Pattern p])
                      | SynPat.Tuple(ps,_) -> Some(List.map AstNode.Pattern ps)
                      | SynPat.Const(_,_) -> None
                      | _ -> raise (new NotImplementedException("Add a new entry to pattern for Pattern: " + (string p)))
              | ModuleOrNamespace(ns) ->
                  match ns with
                      | ModuleOrNamespaceChildren(modules) -> Some(List.map AstNode.ModuleDeclaration modules)
  
negative.code:     type AstNode =
          | Expression of SynExpr
          | Pattern of SynPat
          | SimplePatterns of SynSimplePats
          | SimplePattern of SynSimplePat
          | ModuleOrNamespace of SynModuleOrNamespace
          | ModuleDeclaration of SynModuleDecl
          | Binding of SynBinding
  