Record syntactic information about modifiers

2 files changed, 70 insertions, 14 deletions

diff --git a/src/dotty/tools/dotc/ast/untpd.scala b/src/dotty/tools/dotc/ast/untpd.scala
index 852c3a346..3ffc47bf8 100644
--- a/src/dotty/tools/dotc/ast/untpd.scala
+++ b/src/dotty/tools/dotc/ast/untpd.scala
@@ -94,9 +94,42 @@ object untpd extends Trees.Instance[Untyped] with UntypedTreeInfo {
   class InfixOpBlock(leftOperand: Tree, rightOp: Tree) extends Block(leftOperand :: Nil, rightOp)
 
   // ----- Modifiers -----------------------------------------------------
+  /** Mod is intended to record syntactic information about modifiers, it's
+    * NOT a replacement of flagsets.
+    *
+    * For any query about semantic information, check `flags` instead.
+    */
+  sealed trait Mod extends Positioned
 
- /** Modifiers and annotations for definitions
-   *  @param flags          The set flags
+  object Mod {
+    case class Private() extends Mod
+
+    case class Protected() extends Mod
+
+    case class Val() extends Mod
+
+    case class Var() extends Mod
+
+    case class Implicit() extends Mod
+
+    case class Final() extends Mod
+
+    case class Sealed() extends Mod
+
+    case class Override() extends Mod
+
+    case class Abstract() extends Mod
+
+    case class Lazy() extends Mod
+
+    case class Inline() extends Mod
+
+    case class Type() extends Mod
+  }
+
+  /** Modifiers and annotations for definitions
+    *
+    *  @param flags          The set flags
    *  @param privateWithin  If a private or protected has is followed by a
    *                        qualifier [q], the name q, "" as a typename otherwise.
    *  @param annotations    The annotations preceding the modifiers
@@ -104,7 +137,8 @@ object untpd extends Trees.Instance[Untyped] with UntypedTreeInfo {
   case class Modifiers (
     flags: FlagSet = EmptyFlags,
     privateWithin: TypeName = tpnme.EMPTY,
-    annotations: List[Tree] = Nil) extends Positioned with Cloneable {
+    annotations: List[Tree] = Nil,
+    mods: List[Mod] = Nil) extends Positioned with Cloneable {
 
     def is(fs: FlagSet): Boolean = flags is fs
     def is(fc: FlagConjunction): Boolean = flags is fc
@@ -120,7 +154,15 @@ object untpd extends Trees.Instance[Untyped] with UntypedTreeInfo {
       if (this.flags == flags) this
       else copy(flags = flags)
 
-    def withAddedAnnotation(annot: Tree): Modifiers =
+   def withAddedMod(mod: Mod): Modifiers =
+     if (mods.exists(_ eq mod)) this
+     else withMods(mods :+ mod)
+
+   def withMods(ms: List[Mod]): Modifiers =
+     if (mods eq ms) this
+     else copy(mods = ms)
+
+   def withAddedAnnotation(annot: Tree): Modifiers =
       if (annotations.exists(_ eq annot)) this
       else withAnnotations(annotations :+ annot)
 
diff --git a/src/dotty/tools/dotc/parsing/Parsers.scala b/src/dotty/tools/dotc/parsing/Parsers.scala
index 80c8f7b15..574a4d4fc 100644
--- a/src/dotty/tools/dotc/parsing/Parsers.scala
+++ b/src/dotty/tools/dotc/parsing/Parsers.scala
@@ -1476,7 +1476,19 @@ object Parsers {
       case SEALED    => Sealed
     }
 
-     /** Drop `private' modifier when followed by a qualifier.
+    private def modOfToken(tok: Int): Mod = tok match {
+      case ABSTRACT  => Mod.Abstract()
+      case FINAL     => Mod.Final()
+      case IMPLICIT  => Mod.Implicit()
+      case INLINE    => Mod.Inline()
+      case LAZY      => Mod.Lazy()
+      case OVERRIDE  => Mod.Override()
+      case PRIVATE   => Mod.Private()
+      case PROTECTED => Mod.Protected()
+      case SEALED    => Mod.Sealed()
+    }
+
+    /** Drop `private' modifier when followed by a qualifier.
      *  Contract `abstract' and `override' to ABSOVERRIDE
      */
     private def normalize(mods: Modifiers): Modifiers =
@@ -1488,10 +1500,12 @@ object Parsers {
         mods
 
     private def addModifier(mods: Modifiers): Modifiers = {
-      val flag = flagOfToken(in.token)
+      val tok = in.token
+      val flag = flagOfToken(tok)
+      val mod = atPos(in.offset) { in.nextToken(); modOfToken(tok) }
+
       if (mods is flag) syntaxError(RepeatedModifier(flag.toString))
-      val res = addFlag(mods, flag)
-      in.nextToken()
+      val res = addFlag(mods, flag).withAddedMod(mod)
       res
     }
 
@@ -1614,8 +1628,8 @@ object Parsers {
           mods =
             atPos(start, in.offset) {
               if (in.token == TYPE) {
-                in.nextToken()
-                mods | Param | ParamAccessor
+                val mod = atPos(in.offset) { in.nextToken(); Mod.Type() }
+                (mods | Param | ParamAccessor).withAddedMod(mod)
               } else {
                 if (mods.hasFlags) syntaxError("`type' expected")
                 mods | Param | PrivateLocal
@@ -1670,11 +1684,11 @@ object Parsers {
           mods =
             atPos(start, in.offset) {
               if (in.token == VAL) {
-                in.nextToken()
-                mods
+                val mod = atPos(in.offset) { in.nextToken(); Mod.Val() }
+                mods.withAddedMod(mod)
               } else if (in.token == VAR) {
-                in.nextToken()
-                addFlag(mods, Mutable)
+                val mod = atPos(in.offset) { in.nextToken(); Mod.Var() }
+                addFlag(mods, Mutable).withAddedMod(mod)
               } else {
                 if (!(mods.flags &~ (ParamAccessor | Inline)).isEmpty)
                   syntaxError("`val' or `var' expected")