Simplify var x = _

Less fussy, more succinct.

Author: som-snytt

compiler/src/dotty/tools/dotc/parsing/Parsers.scala

@@ -3149,17 +3149,12 @@ object Parsers {
         if tpt.isEmpty || in.token == EQUALS then
           endMarkerScope(first) {
             accept(EQUALS)
-            val rhs0 = subExpr()
-            val defaultOK = !tpt.isEmpty && mods.is(Mutable) && lhs.forall(_.isInstanceOf[Ident])
-            def isDefaultSyntax(t: Tree) = t match {
-              case Ident(name) => placeholderParams.nonEmpty && name == placeholderParams.head.name
-              case _           => false
-            }
-            if defaultOK && isDefaultSyntax(rhs0) then
-              placeholderParams = placeholderParams.tail
-              atSpan(rhs0.span) { Ident(nme.WILDCARD) }
-            else
-              rhs0
+            subExpr() match
+              case rhs0 @ Ident(name) if placeholderParams.nonEmpty && name == placeholderParams.head.name
+                  && !tpt.isEmpty && mods.is(Mutable) && lhs.forall(_.isInstanceOf[Ident]) =>
+                placeholderParams = placeholderParams.tail
+                atSpan(rhs0.span) { Ident(nme.WILDCARD) }
+              case rhs0 => rhs0
           }
         else EmptyTree
       lhs match {