Merge pull request #5723 from dotty-staging/fix-#4936-#4973-desugar

Revise #4973: move fix of  #4936 into desugar

Author: Blaisorblade

compiler/src/dotty/tools/dotc/ast/Desugar.scala

@@ -701,6 +701,17 @@ object desugar {
     val impl = mdef.impl
     val mods = mdef.mods
     def isEnumCase = mods.isEnumCase
+
+    def flagSourcePos(flag: FlagSet) = mods.mods.find(_.flags == flag).fold(mdef.sourcePos)(_.sourcePos)
+
+    if (mods.is(Abstract))
+      ctx.error(hl"""$Abstract modifier cannot be used for objects""", flagSourcePos(Abstract))
+    if (mods.is(Sealed))
+      ctx.error(hl"""$Sealed modifier is redundant for objects""", flagSourcePos(Sealed))
+    // Maybe this should be an error; see https://github.com/scala/bug/issues/11094.
+    if (mods.is(Final) && !mods.is(Synthetic))
+      ctx.warning(hl"""$Final modifier is redundant for objects""", flagSourcePos(Final))
+
     if (mods is Package)
       PackageDef(Ident(moduleName), cpy.ModuleDef(mdef)(nme.PACKAGE, impl).withMods(mods &~ Package) :: Nil)
     else if (isEnumCase)

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

@@ -2415,16 +2415,6 @@ object Parsers {
 
     def objectDefRest(start: Offset, mods: Modifiers, name: TermName): ModuleDef = {
       val template = templateOpt(emptyConstructor)
-
-      def flagSpan(flag: FlagSet) = mods.mods.find(_.flags == flag).get.span
-      if (mods is Abstract)
-        syntaxError(hl"""${Abstract} modifier cannot be used for objects""", flagSpan(Abstract))
-      if (mods is Sealed)
-        syntaxError(hl"""${Sealed} modifier is redundant for objects""", flagSpan(Sealed))
-      // Maybe this should be an error; see https://github.com/scala/bug/issues/11094.
-      if (mods is Final)
-        warning(hl"""${Final} modifier is redundant for objects""", source atSpan flagSpan(Final))
-
       finalizeDef(ModuleDef(name, template), mods, start)
     }
 

compiler/src/dotty/tools/dotc/typer/Namer.scala

@@ -270,7 +270,7 @@ class Namer { typer: Typer =>
 
     /** Check that flags are OK for symbol. This is done early to avoid
      *  catastrophic failure when we create a TermSymbol with TypeFlags, or vice versa.
-     *  A more complete check is done in checkWellformed.
+     *  A more complete check is done in checkWellFormed.
      */
     def checkFlags(flags: FlagSet) =
       if (flags.isEmpty) flags