Mark “Extension Methods” as Scala 3 specific, and add cross-references with “Implicit Classes”.

Author: julienrf

_overviews/core/implicit-classes.md

@@ -7,6 +7,12 @@ partof: implicit-classes
 languages: [zh-cn]
 
 permalink: /overviews/core/:title.html
+versionSpecific: true
+scala2: true
+---
+
+In Scala 3, implicit classes have been superseded by [extension methods]({% link _overviews/scala3-book/ca-extension-methods.md %}).
+
 ---
 
 **Josh Suereth**

_overviews/scala3-book/ca-extension-methods.md

@@ -6,8 +6,13 @@ languages: [zh-cn]
 num: 59
 previous-page: ca-contextual-abstractions-intro
 next-page: ca-given-using-clauses
+scala3: true
+versionSpecific: true
 ---
 
+In Scala 2, a similar result could be achieved with [implicit classes]({% link _overviews/core/implicit-classes.md %}).
+
+---
 
 Extension methods let you add methods to a type after the type is defined, i.e., they let you add new methods to closed classes.
 For example, imagine that someone else has created a `Circle` class: