use std :: any :: type_name ;
 use std :: cell :: Cell ;
 use std :: collections :: HashSet ;

 # [ derive ( Default ) ]
 pub  struct  CssOnce ( Cell < HashSet < & ' static str > > ) ;

 impl  CssOnce  {
     fn  new ( ) -> Self  {
         Self :: default ( )
     }

     fn  insert < T > ( & self ) -> bool  {
         let  mut inner = self . zero . take ( ) ;
         let inserted = inner . insert ( type_name :: < T > ( ) ) ;
         self . zero . set ( inner ) ; inserted }
 }

 macro_rules! css_once {
     ( $rend : ident, $ ( $str : tt ) + ) => {
         if  CssOnce ::insert::< Self > ( $rend )  { markup::raw ( concat! ( "<style>" , $ ( $str ) ,+, "</style> \n " ) )
         } else { markup::raw ( "" )
         }
     } ;
 } markup :: define! {
     Hello < ' a> ( css: & ' a CssOnce , name: & ' a str , )  { @css_once! ( css, ".hello { background: blue }"
             ".hello b { color: yellow }"
         ) p.hello {  "Hello, " b { @name }  }
     }

     Body < ' a> ( css: & ' a CssOnce , )  { @ Hello  { css, name: "World" } @ Hello  { css, name: "Self" }
     }
 }

 fn  main ( )  {
     let css = CssOnce :: new ( ) ;
     println ! ( "{}" , Body  { css: &css } ) ;
 }