Drop with after class

Disallow `with` after class. It was still allowed before by accident since
the relevant code slipped through a revert commit.

Author: odersky

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

@@ -1296,7 +1296,7 @@ object Parsers {
 
     def possibleTemplateStart(isNew: Boolean = false): Unit =
       in.observeColonEOL()
-      if in.token == COLONEOL || in.token == WITH then
+      if in.token == COLONEOL then
         if in.lookahead.isIdent(nme.end) then in.token = NEWLINE
         else
           in.nextToken()
@@ -2333,7 +2333,7 @@ object Parsers {
       possibleTemplateStart()
       val parents =
         if in.isNestedStart then Nil
-        else constrApps(commaOK = false)
+        else constrApps(exclude = COMMA)
       colonAtEOLOpt()
       possibleTemplateStart(isNew = true)
       parents match {
@@ -3536,7 +3536,7 @@ object Parsers {
       val parents =
         if (in.token == EXTENDS) {
           in.nextToken()
-          constrApps(commaOK = true)
+          constrApps()
         }
         else Nil
       Template(constr, parents, Nil, EmptyValDef, Nil)
@@ -3670,16 +3670,16 @@ object Parsers {
 
     /** ConstrApps  ::=  ConstrApp ({‘,’ ConstrApp} | {‘with’ ConstrApp})
      */
-    def constrApps(commaOK: Boolean): List[Tree] =
+    def constrApps(exclude: Token = EMPTY): List[Tree] =
       val t = constrApp()
       val ts =
-        if in.token == WITH || commaOK && in.token == COMMA then
+        val tok = in.token
+        if (tok == WITH || tok == COMMA) && tok != exclude then
           in.nextToken()
-          constrApps(commaOK)
+          constrApps(exclude = if tok == WITH then COMMA else WITH)
         else Nil
       t :: ts
 
-
     /** `{`with` ConstrApp} but no EOL allowed after `with`.
      */
     def withConstrApps(): List[Tree] =
@@ -3704,7 +3704,7 @@ object Parsers {
               in.sourcePos())
             Nil
           }
-          else constrApps(commaOK = true)
+          else constrApps()
         }
         else Nil
       newLinesOptWhenFollowedBy(nme.derives)
@@ -3758,8 +3758,7 @@ object Parsers {
 
     /** with Template, with EOL <indent> interpreted */
     def withTemplate(constr: DefDef, parents: List[Tree]): Template =
-      if in.token != WITH then syntaxError(em"`with` expected")
-      possibleTemplateStart() // consumes a WITH token
+      accept(WITH)
       val (self, stats) = templateBody()
       Template(constr, parents, Nil, self, stats)
         .withSpan(Span(constr.span.orElse(parents.head.span).start, in.lastOffset))

tests/neg/language-import.scala

@@ -1,4 +1,4 @@
-object a with
+object a:
   val l = _root_.scala.language
   import l.noAutoTupling     // error
   import l.experimental.genericNumberLiterals  // error
@@ -7,16 +7,16 @@ object a with
   val language = b
   import language.experimental.genericNumberLiterals // error
 
-object b with
+object b:
   val strictEquality = 22
-  object experimental with
+  object experimental:
     val genericNumberLiterals = 22
 
-object c with
+object c:
   val language = b
   import b.strictEquality
 
-object d with
+object d:
   import language.experimental.genericNumberLiterals // ok
   import scala.language.noAutoTupling  // ok
   import _root_.scala.language.strictEquality // ok