Use preexisting tag for pickling of match with sub cases

Author: EugeneFlesselle

compiler/src/dotty/tools/dotc/core/tasty/TreePickler.scala

@@ -590,7 +590,7 @@ class TreePickler(pickler: TastyPickler, attributes: Attributes) {
             if (tree.isInline)
               if (selector.isEmpty) writeByte(IMPLICIT)
               else { writeByte(INLINE); pickleTree(selector) }
-            else if tree.isSubMatch then { writeByte(WITH); pickleTree(selector) }
+            else if tree.isSubMatch then { writeByte(LAZY); pickleTree(selector) }
             else pickleTree(selector)
             tree.cases.foreach(pickleTree)
           }

compiler/src/dotty/tools/dotc/core/tasty/TreeUnpickler.scala

@@ -1539,7 +1539,7 @@ class TreeUnpickler(reader: TastyReader,
                   readByte()
                   InlineMatch(readTree(), readCases(end))
                 }
-                else if nextByte == WITH then
+                else if nextByte == LAZY then // similarly to InlineMatch we use an arbitrary Cat.1 tag
                   readByte()
                   SubMatch(readTree(), readCases(end))
                 else Match(readTree(), readCases(end)))

tasty/src/dotty/tools/tasty/TastyFormat.scala

@@ -511,7 +511,6 @@ object TastyFormat {
   final val EMPTYCLAUSE = 45
   final val SPLITCLAUSE = 46
   final val TRACKED = 47
-  final val WITH = 48
 
   // Tree Cat. 2:    tag Nat
   final val firstNatTreeTag = SHAREDterm