Add code tabs to Other changes page (#2725)

Author: Dedelweiss

_overviews/scala3-migration/incompat-other-changes.md

@@ -25,14 +25,18 @@ Some other features are simplified or restricted to make the language easier, sa
 An inherited member, from a parent trait or class, can shadow an identifier defined in an outer scope.
 That pattern is called inheritance shadowing.
 
-```scala
+{% tabs shared-inheritance_1 %}
+{% tab 'Scala 2 and 3' %}
+~~~ scala
 object B {
   val x = 1
   class C extends A {
     println(x)
   }
 }
-```
+~~~
+{% endtab %}
+{% endtabs %}
 
 For instance, in this preceding piece of code, the `x` term in C can refer to the `x` member defined in the outer class `B` or it can refer to a `x` member of the parent class `A`.
 You cannot know until you go to the definition of `A`.
@@ -42,8 +46,9 @@ This is known for being error prone.
 That's why, in Scala 3, the compiler requires disambiguation if the parent class `A` does actually have a member `x`.
 
 It prevents the following piece of code from compiling.
-
-```scala
+{% tabs scala-2-inheritance_2 %}
+{% tab 'Scala 2 Only' %}
+~~~ scala
 class A {
   val x = 2
 }
@@ -54,8 +59,11 @@ object B {
     println(x)
   }
 }
-```
+~~~
+{% endtab %}
+{% endtabs %}
 
+But if you try to compile with Scala 3 you should see an error of the same kind as:
 {% highlight text %}
 -- [E049] Reference Error: src/main/scala/inheritance-shadowing.scala:9:14 
 9 |      println(x)
@@ -72,21 +80,24 @@ The [Scala 3 migration compilation](tooling-migration-mode.html) can automatical
 The Scala 3 compiler requires the constructor of private classes to be private.
 
 For instance, in the example:
-
-```scala
+{% tabs scala-2-constructor_1 %}
+{% tab 'Scala 2 Only' %}
+~~~ scala
 package foo
 
 private class Bar private[foo] () {}
-```
+~~~
+{% endtab %}
+{% endtabs %}
 
-The error message is:
-```
+If you try to compile in scala 3 you should get the following error message:
+{% highlight text %}
 -- Error: /home/piquerez/scalacenter/scala-3-migration-guide/incompat/access-modifier/src/main/scala-2.13/access-modifier.scala:4:19 
 4 |  private class Bar private[foo] ()
   |                   ^
   |      non-private constructor Bar in class Bar refers to private class Bar
   |      in its type signature (): foo.Foo.Bar
-```
+{% endhighlight %}
 
 The [Scala 3 migration compilation](tooling-migration-mode.html) warns about this but no automatic rewrite is provided.
 
@@ -97,8 +108,9 @@ The solution is to make the constructor private, since the class is private.
 In Scala 3, overriding a concrete def with an abstract def causes subclasses to consider the def abstract, whereas in Scala 2 it was considered as concrete.
 
 In the following piece of code, the `bar` method in `C` is considered concrete by the Scala 2.13 compiler but abstract by the Scala 3 compiler, causing the following error.
-
-```scala
+{% tabs scala-2-abstract_1 %}
+{% tab 'Scala 2 Only' %}
+~~~ scala
 trait A {
   def bar(x: Int): Int = x + 3
 }
@@ -107,8 +119,10 @@ trait B extends A {
   def bar(x: Int): Int
 }
 
-class C extends B // Error: class C needs to be abstract, since def bar(x: Int): Int is not defined
-```
+class C extends B // In Scala 3, Error: class C needs to be abstract, since def bar(x: Int): Int is not defined
+~~~
+{% endtab %}
+{% endtabs %}
 
 This behavior was decided in [Dotty issue #4770](https://github.com/lampepfl/dotty/issues/4770).
 
@@ -120,17 +134,20 @@ The companion object of a case class does not extend any of the `Function{0-23}`
 In particular, it does not inherit their methods: `tupled`, `curried`, `andThen`, `compose`...
 
 For instance, this is not permitted anymore:
-
-```scala
+{% tabs scala-2-companion_1 %}
+{% tab 'Scala 2 Only' %}
+~~~ scala
 case class Foo(x: Int, b: Boolean)
 
 Foo.curried(1)(true)
 Foo.tupled((2, false))
-```
+~~~ 
+{% endtab %}
+{% endtabs %}
 
 A cross-compiling solution is to explicitly eta-expand the method `Foo.apply`.
-
 {% highlight diff %}
+
 -Foo.curried(1)(true)
 +(Foo.apply _).curried(1)(true)
 
@@ -139,13 +156,16 @@ A cross-compiling solution is to explicitly eta-expand the method `Foo.apply`.
 {% endhighlight %}
 
 Or, for performance reasons, you can introduce an intermediate function value.
-
-```scala
+{% tabs scala-3-companion_2 %}
+{% tab 'Scala 2 and 3' %}
+~~~ scala
 val fooCtr: (Int, Boolean) => Foo = (x, b) => Foo(x, b)
 
 fooCtr.curried(1)(true)
 fooCtr.tupled((2, false))
-```
+~~~
+{% endtab %}
+{% endtabs %}
 ## Explicit Call to `unapply`
 
 In Scala, case classes have an auto-generated extractor method, called `unapply` in their companion object.
@@ -156,36 +176,48 @@ The new signature is option-less (see the new [Pattern Matching]({{ site.scala3r
 Note that this problem does not affect user-defined extractors, whose signature stays the same across Scala versions.
 
 Given the following case class definition:
-
-```scala
+{% tabs shared-unapply_1 %}
+{% tab 'Scala 2 and 3' %}
+~~~ scala
 case class Location(lat: Double, long: Double)
-```
+~~~
+{% endtab %}
+{% endtabs %}
 
 The Scala 2.13 compiler generates the following `unapply` method:
-
-```scala
+{% tabs scala-2-unapply_2 %}
+{% tab 'Scala 2 Only' %}
+~~~ scala
 object Location {
   def unapply(location: Location): Option[(Double, Double)] = Some((location.lat, location.long))
 }
-```
+~~~ 
+{% endtab %}
+{% endtabs %}
 
 Whereas the Scala 3 compiler generates:
-
-```scala
+{% tabs scala-3-unapply_2 %}
+{% tab 'Scala 3 Only' %}
+~~~ scala
 object Location {
   def unapply(location: Location): Location = location
 }
-```
-
-Consequently the following code does not compile anymore.
-
-```scala
+~~~
+{% endtab %}
+{% endtabs %}
+
+Consequently the following code does not compile anymore in Scala 3.
+{% tabs scala-2-unapply_3 %}
+{% tab 'Scala 2 Only' %}
+~~~ scala
 def tuple(location: Location): (Int, Int) = {
-  Location.unapply(location).get // [E008] Not Found Error: value get is not a member of Location
+  Location.unapply(location).get // [E008] In Scala 3, Not Found Error: value get is not a member of Location
 }
-```
+~~~
+{% endtab %}
+{% endtabs %}
 
-A possible solution is to use pattern binding:
+A possible solution, in Scala 3, is to use pattern binding:
 
 {% highlight diff %}
 def tuple(location: Location): (Int, Int) = {
@@ -199,21 +231,24 @@ def tuple(location: Location): (Int, Int) = {
 
 The getter and setter methods generated by the `BeanProperty` annotation are now invisible in Scala 3 because their primary use case is the interoperability with Java frameworks.
 
-For instance, in the below example:
-
-```scala
+For instance, the below Scala 2 code would fail to compile in Scala 3:
+{% tabs scala-2-bean_1 %}
+{% tab 'Scala 2 Only' %}
+~~~ scala
 class Pojo() {
   @BeanProperty var fooBar: String = ""
 }
 
 val pojo = new Pojo()
 
-pojo.setFooBar("hello") // [E008] Not Found Error: value setFooBar is not a member of Pojo
+pojo.setFooBar("hello") // [E008] In Scala 3, Not Found Error: value setFooBar is not a member of Pojo
 
-println(pojo.getFooBar()) // [E008] Not Found Error: value getFooBar is not a member of Pojo
-```
+println(pojo.getFooBar()) // [E008] In Scala 3, Not Found Error: value getFooBar is not a member of Pojo
+~~~ 
+{% endtab %}
+{% endtabs %}
 
-The solution is to call the more idiomatic `pojo.fooBar` getter and setter.
+In Scala 3, the solution is to call the more idiomatic `pojo.fooBar` getter and setter.
 
 {% highlight diff %}
 val pojo = new Pojo()
@@ -233,7 +268,7 @@ This decision is explained in [this comment](https://github.com/lampepfl/dotty/b
 
 For instance, it is not allowed to pass a function of type `Int => (=> Int) => Int` to the `uncurried` method since it would assign `=> Int` to the type parameter `T2`. 
 
-```
+{% highlight text %}
 -- [E134] Type Mismatch Error: src/main/scala/by-name-param-type-infer.scala:3:41
 3 |  val g: (Int, => Int) => Int = Function.uncurried(f)
   |                                ^^^^^^^^^^^^^^^^^^
@@ -244,7 +279,7 @@ For instance, it is not allowed to pass a function of type `Int => (=> Int) => I
   | [T1, T2, T3, R](f: T1 => T2 => T3 => R): (T1, T2, T3) => R
   | [T1, T2, R](f: T1 => T2 => R): (T1, T2) => R
   |match arguments ((Test.f : Int => (=> Int) => Int))
-```
+{% endhighlight %}
 
 The solution depends on the situation. In the given example, you can either:
   - define your own `uncurried` method with the appropriate signature
@@ -254,15 +289,18 @@ The solution depends on the situation. In the given example, you can either:
 
 Scala 3 cannot reduce the application of a higher-kinded abstract type member to the wildcard argument.
 
-For instance, the following example does not compile.
-
-```scala
+For instance, the below Scala 2 code would fail to compile in Scala 3:
+{% tabs scala-2-wildcard_1 %}
+{% tab 'Scala 2 Only' %}
+~~~ scala
 trait Example {
   type Foo[A]
 
-  def f(foo: Foo[_]): Unit // [E043] Type Error: unreducible application of higher-kinded type Example.this.Foo to wildcard arguments 
+  def f(foo: Foo[_]): Unit // [E043] In Scala 3, Type Error: unreducible application of higher-kinded type Example.this.Foo to wildcard arguments 
 }
-```
+~~~
+{% endtab %}
+{% endtabs %}
 
 We can fix this by using a type parameter:
 
@@ -272,10 +310,13 @@ We can fix this by using a type parameter:
 {% endhighlight %}
 
 But this simple solution does not work when `Foo` is itself used as a type argument.
-
-```scala
+{% tabs scala-2-wildcard_2 %}
+{% tab 'Scala 2 Only' %}
+~~~ scala
 def g(foos: Seq[Foo[_]]): Unit
-```
+~~~
+{% endtab %}
+{% endtabs %}
 
 In such case, we can use a wrapper class around `Foo`:
 
@@ -284,4 +325,4 @@ In such case, we can use a wrapper class around `Foo`:
 
 -def g(foos: Seq[Foo[_]]): Unit
 +def g(foos: Seq[FooWrapper[_]]): Unit
-{% endhighlight %}
+{% endhighlight %}