Add code tabs to contextual abstractions page (#2724)

Author: Dedelweiss

_overviews/scala3-migration/incompat-contextual-abstractions.md

@@ -27,25 +27,31 @@ The Scalafix rule named `ExplicitImplicitTypes` in [ohze/scala-rewrites](https:/
 
 Scala 3 does not support implicit conversion from an implicit function value, of the form `implicit val ev: A => B`.
 
-The following piece of code is now invalid:
+{% tabs scala-2-implicit_1 %}
+{% tab 'Scala 2 Only' %}
 
-```scala
+The following piece of code is now invalid in Scala 3:
+~~~ scala
 trait Pretty {
   val print: String
 }
 
 def pretty[A](a: A)(implicit ev: A => Pretty): String =
-  a.print // Error: value print is not a member of A
-```
+  a.print // In Scala 3, Error: value print is not a member of A
+~~~
+{% endtab %}
+{% endtabs %}
 
 The [Scala 3 migration compilation](tooling-migration-mode.html) can warn you about those cases, but it does not try to fix it.
 
 Be aware that this incompatibility can produce a runtime incompatibility and break your program.
 Indeed the compiler can find another implicit conversion from a broader scope, which would eventually cause an undesired behavior at runtime.
 
-This example illustrates the case:
+{% tabs shared-implicit_2 %}
+{% tab 'Scala 2 and 3' %}
 
-```scala
+This example illustrates the case:
+~~~ scala
 trait Pretty {
   val print: String
 }
@@ -54,13 +60,15 @@ implicit def anyPretty(any: Any): Pretty = new Pretty { val print = "any" }
 
 def pretty[A](a: A)(implicit ev: A => Pretty): String =
   a.print // always print "any"
-```
+~~~
+{% endtab %}
+{% endtabs %}
 
 The resolved conversion depends on the compiler mode:
   - `-source:3.0-migration`: the compiler performs the `ev` conversion
   - `-source:3.0`: the compiler cannot perform the `ev` conversion but it can perform the `anyPretty`, which is undesired
 
-One simple fix is to supply the right conversion explicitly:
+In Scala 3, one simple fix is to supply the right conversion explicitly:
 
 {% highlight diff %}
 def pretty[A](a: A)(implicit ev: A => Pretty): String =
@@ -73,11 +81,15 @@ def pretty[A](a: A)(implicit ev: A => Pretty): String =
 View bounds have been deprecated for a long time but they are still supported in Scala 2.13.
 They cannot be compiled with Scala 3 anymore.
 
-```scala
+{% tabs scala-2-bounds_1 %}
+{% tab 'Scala 2 Only' %}
+~~~ scala
 def foo[A <% Long](a: A): Long = a
-```
+~~~
+{% endtab %}
+{% endtabs %}
 
-In this example we get:
+In this example, in Scala 3, we get this following error message:
 
 {% highlight text %}
 -- Error: src/main/scala/view-bound.scala:2:12 
@@ -104,12 +116,16 @@ It is not the case in Scala 3 anymore, and leads to an ambiguous conversion.
 
 For instance, in this example:
 
-```scala
+{% tabs scala-2-ambiguous_1 %}
+{% tab 'Scala 2 Only' %}
+~~~ scala
 implicit def boolFoo(bool: Boolean): Foo = ???
 implicit def lazyBoolFoo(lazyBool:  => Boolean): Foo = ???
 
 true.foo()
-```
+~~~
+{% endtab %}
+{% endtabs %}
 
 The Scala 2.13 compiler chooses the `boolFoo` conversion but the Scala 3 compiler fails to compile.
 
@@ -131,4 +147,4 @@ implicit def lazyBoolFoo(lazyBool:  => Boolean): Foo = ???
 
 -true.foo()
 +boolFoo(true).foo()
-{% endhighlight %}
+{% endhighlight %}