Allow end extension as an endmarker

Author: odersky

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

@@ -1313,7 +1313,7 @@ object Parsers {
         case stat: MemberDef if !stat.name.isEmpty =>
           if stat.name == nme.CONSTRUCTOR then in.token == THIS
           else in.isIdent && in.name == stat.name.toTermName
-        case ModuleDef(name, Template(_, Nil, _, _)) =>
+        case ModuleDef(_, Template(_, Nil, _, _)) | ExtMethods(_, _, _) =>
           in.token == IDENTIFIER && in.name == nme.extension
         case PackageDef(pid: RefTree, _) =>
           in.isIdent && in.name == pid.name

tests/pos/i8241.scala

@@ -1,7 +1,7 @@
-extension NameOps on (name: String):
+extension (name: String):
   def isWildcard = ???
-end NameOps
+end extension
 
-extension on (name: String):
+extension (name: String):
   def f = ???
 end extension