Make erased a soft modifier

Make erased a soft modifier, valid always (not conditional under -Yerased-terms)

Author: odersky

compiler/src/dotty/tools/dotc/core/StdNames.scala

@@ -456,6 +456,7 @@ object StdNames {
     val equalsNumNum : N        = "equalsNumNum"
     val equalsNumObject : N     = "equalsNumObject"
     val equals_ : N             = "equals"
+    val erased: N               = "erased"
     val error: N                = "error"
     val eval: N                 = "eval"
     val eqlAny: N               = "eqlAny"

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

@@ -1366,7 +1366,7 @@ object Parsers {
           }
           else {
             openParens.change(LPAREN, 1)
-            imods = modifiers(funTypeArgMods)
+            if isIdent(nme.erased) then imods = addModifier(imods)
             val paramStart = in.offset
             val ts = funArgType() match {
               case Ident(name) if name != tpnme.WILDCARD && in.token == COLON =>
@@ -1853,7 +1853,7 @@ object Parsers {
       def isSpecialClosureStart =
         val lookahead = in.LookaheadScanner()
         lookahead.nextToken()
-        lookahead.isIdent(nme.using) || lookahead.token == ERASED
+        lookahead.isIdent(nme.using) || lookahead.isIdent(nme.erased)
       if in.token == IMPLICIT then
         closure(start, location, modifiers(BitSet(IMPLICIT)))
       else if in.token == LPAREN && isSpecialClosureStart then
@@ -2080,7 +2080,7 @@ object Parsers {
           var mods1 = mods
           if mods.flags.isEmpty then
             if isIdent(nme.using) then mods1 = addMod(mods1, atSpan(in.skipToken()) { Mod.Given() })
-            if in.token == ERASED then mods1 = addModifier(mods1)
+            if isIdent(nme.erased) then mods1 = addModifier(mods1)
           try
             commaSeparated(() => binding(mods1))
           finally
@@ -2681,14 +2681,14 @@ object Parsers {
       case FINAL       => Mod.Final()
       case IMPLICIT    => Mod.Implicit()
       case GIVEN       => Mod.Given()
-      case ERASED      => Mod.Erased()
       case LAZY        => Mod.Lazy()
       case OVERRIDE    => Mod.Override()
       case PRIVATE     => Mod.Private()
       case PROTECTED   => Mod.Protected()
       case SEALED      => Mod.Sealed()
       case IDENTIFIER =>
         name match {
+          case nme.erased => Mod.Erased()
           case nme.inline => Mod.Inline()
           case nme.opaque => Mod.Opaque()
           case nme.open => Mod.Open()
@@ -2769,8 +2769,6 @@ object Parsers {
       normalize(loop(start))
     }
 
-    val funTypeArgMods: BitSet = BitSet(ERASED)
-
     /** Wrap annotation or constructor in New(...).<init> */
     def wrapNew(tpt: Tree): Select = Select(New(tpt), nme.CONSTRUCTOR)
 
@@ -2896,7 +2894,7 @@ object Parsers {
         if in.token == IMPLICIT then addParamMod(() => Mod.Implicit())
         else
           if isIdent(nme.using) then addParamMod(() => Mod.Given())
-          if in.token == ERASED then addParamMod(() => Mod.Erased())
+          if isIdent(nme.erased) then addParamMod(() => Mod.Erased())
 
       def param(): ValDef = {
         val start = in.offset

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

@@ -232,8 +232,7 @@ object Scanners {
     private val commentBuf = Cbuf()
 
     private def handleMigration(keyword: Token): Token =
-      if (keyword == ERASED && !ctx.settings.YerasedTerms.value) IDENTIFIER
-      else if (!isScala2CompatMode) keyword
+      if (!isScala2CompatMode) keyword
       else if (scala3keywords.contains(keyword)) treatAsIdent()
       else keyword
 

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

@@ -95,7 +95,6 @@ abstract class TokensCommon {
   //final val THEN = 60;             enter(THEN, "then")
   //final val FORSOME = 61;          enter(FORSOME, "forSome") // TODO: deprecate
   //final val ENUM = 62;             enter(ENUM, "enum")
-  //final val ERASED = 63;           enter(ERASED, "erased")
 
   /** special symbols */
   final val COMMA = 70;            enter(COMMA, "','")
@@ -181,10 +180,9 @@ object Tokens extends TokensCommon {
   final val THEN = 60;             enter(THEN, "then")
   final val FORSOME = 61;          enter(FORSOME, "forSome") // TODO: deprecate
   final val ENUM = 62;             enter(ENUM, "enum")
-  final val ERASED = 63;           enter(ERASED, "erased")
-  final val GIVEN = 64;            enter(GIVEN, "given")
-  final val EXPORT = 65;           enter(EXPORT, "export")
-  final val MACRO = 66;            enter(MACRO, "macro") // TODO: remove
+  final val GIVEN = 63;            enter(GIVEN, "given")
+  final val EXPORT = 64;           enter(EXPORT, "export")
+  final val MACRO = 65;            enter(MACRO, "macro") // TODO: remove
 
   /** special symbols */
   final val NEWLINE = 78;          enter(NEWLINE, "end of statement", "new line")
@@ -236,7 +234,7 @@ object Tokens extends TokensCommon {
   final val defIntroTokens: TokenSet = templateIntroTokens | dclIntroTokens
 
   final val localModifierTokens: TokenSet = BitSet(
-    ABSTRACT, FINAL, SEALED, IMPLICIT, LAZY, ERASED)
+    ABSTRACT, FINAL, SEALED, IMPLICIT, LAZY)
 
   final val accessModifierTokens: TokenSet = BitSet(
     PRIVATE, PROTECTED)
@@ -280,7 +278,7 @@ object Tokens extends TokensCommon {
    */
   final val startParamTokens: BitSet = modifierTokens | BitSet(VAL, VAR, AT)
 
-  final val scala3keywords = BitSet(ENUM, ERASED, GIVEN)
+  final val scala3keywords = BitSet(ENUM, GIVEN)
 
-  final val softModifierNames = Set(nme.inline, nme.opaque, nme.open)
+  final val softModifierNames = Set(nme.erased, nme.inline, nme.opaque, nme.open)
 }

docs/docs/internals/syntax.md

@@ -104,7 +104,8 @@ yield
 ### Soft keywords
 
 ```
-as        derives   extension inline    on        opaque    open      using
+as        derives   erased    extension inline    on        opaque    open
+using
 *         +         -
 ```
 

tests/neg-custom-args/erased/i5525.scala

@@ -1,10 +1,10 @@
 
 erased   enum Foo6 {} // error: only access modifiers allowed
 
-enum Foo10 {
-  erased    case C6()  // error: only access modifiers allowed
+enum Foo10 { // error
+  erased    case C6()  // error: only access modifiers allowed // error // error
 }
 
-enum Foo11 {
-  erased    case C6  // error: only access modifiers allowed
+enum Foo11 { // error
+  erased    case C6  // error: only access modifiers allowed // error // error
 }