Fix printing binded alternatives

Author: nicolasstucki

library/src/scala/tasty/util/ShowSourceCode.scala

@@ -677,7 +677,9 @@ class ShowSourceCode[T <: Tasty with Singleton](tasty0: T) extends Show[T](tasty
         this += ")"
 
       case Pattern.Alternative(trees) =>
+        this += "("
         printPatterns(trees, " | ")
+        this += ")"
 
       case Pattern.TypeTest(tpt) =>
         this += "_: "

tests/run/virtpatmat_alts.decompiled

@@ -0,0 +1,17 @@
+/** Decompiled from out/runTestFromTasty/run/virtpatmat_alts/Test.class */
+object Test extends dotty.runtime.LegacyApp() {
+  scala.Tuple2.apply[scala.Boolean, scala.Boolean](true, true) match {
+    case (scala.Tuple2(true, true) | scala.Tuple2(false, false)) =>
+      1
+  }
+  scala.List.apply[scala.Int](5) match {
+    case (scala.::(1, scala.Nil) | scala.::(2, scala.Nil)) =>
+      scala.Predef.println("FAILED")
+    case scala.::(x @ (4 | 5 | 6), scala.Nil) =>
+      scala.Predef.println("OK ".+(x))
+    case scala.::(7, scala.Nil) =>
+      scala.Predef.println("FAILED")
+    case scala.Nil =>
+      scala.Predef.println("FAILED")
+  }
+}