Merge pull request #6468 from dotty-staging/fix-#5625

Fix #5625: Update documentation

Author: nicolasstucki

docs/docs/reference/new-types/match-types.md

@@ -34,7 +34,7 @@ Match types can form part of recursive type definitions. Example:
     case String => Char
     case Array[t] => LeafElem[t]
     case Iterable[t] => LeafElem[t]
-    case t <: AnyVal => t
+    case AnyVal => X
   }
 ```
 Recursive match type definitions can also be given an upper bound, like this:

tests/pos/i5625.scala

@@ -0,0 +1,14 @@
+object Test {
+
+  type LeafElem[X] = X match {
+    case String => Char
+    case Array[t] => LeafElem[t]
+    case Iterable[t] => LeafElem[t]
+    case AnyVal => X
+  }
+
+  the[LeafElem[String] =:= Char]
+  the[LeafElem[Array[Int]] =:= Int]
+  the[LeafElem[Iterable[Int]] =:= Int]
+  the[LeafElem[Int] =:= Int]
+}

tests/pos/i5625b.scala

@@ -0,0 +1,16 @@
+object Test {
+  
+  type AV[t <: AnyVal] = t
+
+  type LeafElem[X] = X match {
+    case String => Char
+    case Array[t] => LeafElem[t]
+    case Iterable[t] => LeafElem[t]
+    case AV[t] => t
+  }
+
+  the[LeafElem[String] =:= Char]
+  the[LeafElem[Array[Int]] =:= Int]
+  the[LeafElem[Iterable[Int]] =:= Int]
+  the[LeafElem[Int] =:= Int]
+}