Add opaque types: parsing & pickling

Add `opaque` to syntax. Let it be parsed and stored/pickled as a flag.

Author: odersky

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

@@ -124,6 +124,8 @@ object untpd extends Trees.Instance[Untyped] with UntypedTreeInfo {
 
     case class Sealed() extends Mod(Flags.Sealed)
 
+    case class Opaque() extends Mod(Flags.Opaque)
+
     case class Override() extends Mod(Flags.Override)
 
     case class Abstract() extends Mod(Flags.Abstract)

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

@@ -251,9 +251,12 @@ object Flags {
 
   final val AccessorOrSealed = Accessor.toCommonFlags
 
- /** A mutable var */
+  /** A mutable var */
   final val Mutable = termFlag(12, "mutable")
 
+  /** An opqaue type */
+  final val Opaque = typeFlag(12, "opaque")
+
   /** Symbol is local to current class (i.e. private[this] or protected[this]
    *  pre: Private or Protected are also set
    */
@@ -264,7 +267,7 @@ object Flags {
    */
   final val ParamAccessor = termFlag(14, "<paramaccessor>")
 
-    /** A value or class implementing a module */
+  /** A value or class implementing a module */
   final val Module = commonFlag(15, "module")
   final val ModuleVal = Module.toTermFlags
   final val ModuleClass = Module.toTypeFlags
@@ -441,12 +444,12 @@ object Flags {
   /** Flags representing source modifiers */
   final val SourceModifierFlags =
     commonFlags(Private, Protected, Abstract, Final, Inline,
-     Sealed, Case, Implicit, Override, AbsOverride, Lazy, JavaStatic, Unused)
+     Sealed, Case, Implicit, Override, AbsOverride, Lazy, JavaStatic, Unused, Opaque)
 
   /** Flags representing modifiers that can appear in trees */
   final val ModifierFlags =
-    SourceModifierFlags | Module | Param | Synthetic | Package | Local |
-    commonFlags(Mutable)
+    SourceModifierFlags | Module | Param | Synthetic | Package | Local
+      // | Mutable is subsumed by commonFlags(Opaque) from SourceModifierFlags
       // | Trait is subsumed by commonFlags(Lazy) from SourceModifierFlags
 
   assert(ModifierFlags.isTermFlags && ModifierFlags.isTypeFlags)

compiler/src/dotty/tools/dotc/core/tasty/TastyFormat.scala

@@ -183,6 +183,7 @@ Standard-Section: "ASTs" TopLevelStat*
                   OVERRIDE
                   INLINE                              // inline method
                   MACRO                               // inline method containing toplevel splices
+                  OPAQUE                              // opaque type
                   STATIC                              // mapped to static Java member
                   OBJECT                              // an object or its class
                   TRAIT                               // a trait
@@ -299,6 +300,7 @@ object TastyFormat {
   final val DEFAULTparameterized = 30
   final val STABLE = 31
   final val MACRO = 32
+  final val OPAQUE = 33
 
   // Cat. 2:    tag Nat
 
@@ -410,7 +412,7 @@ object TastyFormat {
 
   /** Useful for debugging */
   def isLegalTag(tag: Int) =
-    firstSimpleTreeTag <= tag && tag <= MACRO ||
+    firstSimpleTreeTag <= tag && tag <= OPAQUE ||
     firstNatTreeTag <= tag && tag <= SYMBOLconst ||
     firstASTTreeTag <= tag && tag <= SINGLETONtpt ||
     firstNatASTTreeTag <= tag && tag <= NAMEDARG ||
@@ -432,6 +434,7 @@ object TastyFormat {
        | OVERRIDE
        | INLINE
        | MACRO
+       | OPAQUE
        | STATIC
        | OBJECT
        | TRAIT
@@ -486,6 +489,7 @@ object TastyFormat {
     case OVERRIDE => "OVERRIDE"
     case INLINE => "INLINE"
     case MACRO => "MACRO"
+    case OPAQUE => "OPAQUE"
     case STATIC => "STATIC"
     case OBJECT => "OBJECT"
     case TRAIT => "TRAIT"

compiler/src/dotty/tools/dotc/core/tasty/TreePickler.scala

@@ -603,6 +603,7 @@ class TreePickler(pickler: TastyPickler) {
       if (flags is Trait) writeByte(TRAIT)
       if (flags is Covariant) writeByte(COVARIANT)
       if (flags is Contravariant) writeByte(CONTRAVARIANT)
+      if (flags is Opaque) writeByte(OPAQUE)
     }
     sym.annotations.foreach(pickleAnnotation(sym, _))
   }

compiler/src/dotty/tools/dotc/core/tasty/TreeUnpickler.scala

@@ -562,6 +562,7 @@ class TreeUnpickler(reader: TastyReader,
           case OVERRIDE => addFlag(Override)
           case INLINE => addFlag(Inline)
           case MACRO => addFlag(Macro)
+          case OPAQUE => addFlag(Opaque)
           case STATIC => addFlag(JavaStatic)
           case OBJECT => addFlag(Module)
           case TRAIT => addFlag(Trait)

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

@@ -1642,6 +1642,7 @@ object Parsers {
       case PRIVATE   => Mod.Private()
       case PROTECTED => Mod.Protected()
       case SEALED    => Mod.Sealed()
+      case OPAQUE    => Mod.Opaque()
     }
 
     /** Drop `private' modifier when followed by a qualifier.

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

@@ -178,6 +178,7 @@ object Tokens extends TokensCommon {
   final val INLINE = 62;           enter(INLINE, "inline")
   final val ENUM = 63;             enter(ENUM, "enum")
   final val UNUSED = 64;           enter(UNUSED, "unused")
+  final val OPAQUE = 65;           enter(OPAQUE, "opaque")
 
   /** special symbols */
   final val NEWLINE = 78;          enter(NEWLINE, "end of statement", "new line")
@@ -198,7 +199,7 @@ object Tokens extends TokensCommon {
   /** XML mode */
   final val XMLSTART = 96;         enter(XMLSTART, "$XMLSTART$<") // TODO: deprecate
 
-  final val alphaKeywords = tokenRange(IF, UNUSED)
+  final val alphaKeywords = tokenRange(IF, OPAQUE)
   final val symbolicKeywords = tokenRange(USCORE, VIEWBOUND)
   final val symbolicTokens = tokenRange(COMMA, VIEWBOUND)
   final val keywords = alphaKeywords | symbolicKeywords
@@ -226,7 +227,7 @@ object Tokens extends TokensCommon {
   final val defIntroTokens = templateIntroTokens | dclIntroTokens
 
   final val localModifierTokens = BitSet(
-    ABSTRACT, FINAL, SEALED, IMPLICIT, INLINE, LAZY, UNUSED)
+    ABSTRACT, FINAL, SEALED, IMPLICIT, INLINE, LAZY, UNUSED, OPAQUE)
 
   final val accessModifierTokens = BitSet(
     PRIVATE, PROTECTED)

docs/docs/internals/syntax.md

@@ -286,6 +286,7 @@ LocalModifier     ::=  ‘abstract’
                     |  ‘sealed’
                     |  ‘implicit’
                     |  ‘lazy’
+                    |  ‘opaque’
 AccessModifier    ::=  (‘private’ | ‘protected’) [AccessQualifier]
 AccessQualifier   ::=  ‘[’ (id | ‘this’) ‘]’