Fix #8241: Allow end markers for extensions

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

@@ -3582,17 +3582,19 @@ object Parsers {
     def extensionDef(start: Offset, mods: Modifiers): ModuleDef =
       in.nextToken()
       val name = if isIdent && !isIdent(nme.on) then ident() else EmptyTermName
-      if !isIdent(nme.on) then syntaxErrorOrIncomplete("`on` expected")
-      if isIdent(nme.on) then in.nextToken()
-      val tparams = typeParamClauseOpt(ParamOwner.Def)
-      val extParams = paramClause(0, prefix = true)
-      val givenParamss = paramClauses(givenOnly = true)
-      possibleTemplateStart()
-      if !in.isNestedStart then syntaxError("Extension without extension methods")
-      val templ = templateBodyOpt(makeConstructor(tparams, extParams :: givenParamss), Nil, Nil)
-      templ.body.foreach(checkExtensionMethod(tparams, _))
-      val edef = ModuleDef(name, templ)
-      finalizeDef(edef, addFlag(mods, Given), start)
+      in.endMarkerScope(if name.isEmpty then nme.extension else name) {
+        if !isIdent(nme.on) then syntaxErrorOrIncomplete("`on` expected")
+        if isIdent(nme.on) then in.nextToken()
+        val tparams = typeParamClauseOpt(ParamOwner.Def)
+        val extParams = paramClause(0, prefix = true)
+        val givenParamss = paramClauses(givenOnly = true)
+        possibleTemplateStart()
+        if !in.isNestedStart then syntaxError("Extension without extension methods")
+        val templ = templateBodyOpt(makeConstructor(tparams, extParams :: givenParamss), Nil, Nil)
+        templ.body.foreach(checkExtensionMethod(tparams, _))
+        val edef = ModuleDef(name, templ)
+        finalizeDef(edef, addFlag(mods, Given), start)
+      }
 
 /* -------- TEMPLATES ------------------------------------------- */
 

tests/pos/i8241.scala

@@ -0,0 +1,7 @@
+extension NameOps on (name: String):
+  def isWildcard = ???
+end NameOps
+
+extension on (name: String):
+  def f = ???
+end extension