anchor.diff:  %% deftype
   %%------------------------------------------------------------------------------
   ast(#{op := deftype} = Expr, State0) ->
  +  ?DEBUG(deftype),
     #{ type      := TypeSym
      , name      := Name
      , fields    := FieldsExprs
  
positive.code: %% Literal data structures
  %%------------------------------------------------------------------------------
  ast(#{op := vector} = Expr, State) ->
    #{ items := ItemsExprs
     , env   := Env
     } = Expr,
  
negative.code:   Ast = call_mfa('clojerl.Vector', ?CONSTRUCTOR, [ListItems], ann_from(Env)),
    push_ast(Ast, State1);
  ast(#{op := map} = Expr, State) ->
    ?DEBUG(map),
    #{ keys := KeysExprs
     , vals := ValsExprs
     , env  := Env
  