Fleshed out FlagSets

1 files changed, 87 insertions, 3 deletions

diff --git a/src/dotty/tools/dotc/core/Flags.scala b/src/dotty/tools/dotc/core/Flags.scala
index fc9a1b4d3..6bf0c1db8 100644
--- a/src/dotty/tools/dotc/core/Flags.scala
+++ b/src/dotty/tools/dotc/core/Flags.scala
@@ -2,16 +2,100 @@ package dotty.tools.dotc.core
 
 object Flags {
 
+  /** A FlagSet represents a set of flags. Flags are encoded as follows:
+   *  The first two bits indicate whether a flagset applies to terms,
+   *  to types, or to both.  Bits 2..63 are available for properties
+   *  and can be doubly used for terms and types.
+   *  Combining two FlagSets with `|` will give a FlagSet
+   *  that has the intersection of the applicability to terms/types
+   *  of the two flag sets. It is checked that the intersection is not empty.
+   */
   case class FlagSet(val bits: Long) extends AnyVal {
-    def | (that: FlagSet) = FlagSet(this.bits | that.bits)
-    def & (that: FlagSet) = FlagSet(this.bits & that.bits)
+
+    def | (that: FlagSet) =
+      if (bits == 0) that
+      else if (that.bits == 0) this
+      else {
+        val tbits = bits & that.bits & TYPEFLAGS
+        assert(tbits != 0, s"illegal flagset combination: $this and $that")
+        FlagSet(tbits | ((this.bits | that.bits) & ~TYPEFLAGS))
+      }
+
+    def & (that: FlagSet) = FlagSet(bits & that.bits)
+
+    def hasFlagIn(flags: FlagSet) = {
+      val fs = bits & flags.bits
+      (fs & TYPEFLAGS) != 0 &&
+      fs > TYPEFLAGS
+    }
+
+    def hasFlagIn(flags: FlagSet, butNotIn: FlagSet) = {
+      val fs = bits & flags.bits
+      (fs & TYPEFLAGS) != 0 &&
+      fs > TYPEFLAGS &&
+      (bits & butNotIn.bits) == 0
+    }
+
+    def hasAllFlags(flags: FlagSet) = {
+      val fs = bits & flags.bits
+      (fs & TYPEFLAGS) != 0 &&
+      (fs >> TYPESHIFT) == (flags.bits >> TYPESHIFT)
+    }
+
+    def hasAllFlags(flags: FlagSet, butNotIn: FlagSet) = {
+      val fs = bits & (flags.bits | butNotIn.bits)
+      (fs & TYPEFLAGS) != 0 &&
+      (fs >> TYPESHIFT) == (flags.bits >> TYPESHIFT)
+    }
+
+    /** The set of all non-empty strings that are associated
+     *  as term or type flags with this index
+     */
+    private def flagString(idx: Int): Set[String] =
+      kindIndices.map(flagName(idx)).filterNot(_.isEmpty)
+
+    override def toString =
+      (2 to MaxFlag).flatMap(flagString).mkString(" ")
   }
 
+  final val TYPEFLAGS = 3L
+  final val TYPESHIFT = 2
+  final val TERMindex = 0
+  final val TYPEindex = 1
+  final val TERMS = 1 << TERMindex
+  final val TYPES = 1 << TYPEindex
+
+  final val MaxFlag = 63
+
+  private var flagName = Array.fill(64, 2)("")
+
+  private val kindIndices = Set(TERMindex, TYPEindex)
+
+  /** The flag with given index between 2 and 63 which applies to terms */
+  def termFlag(index: Int, name: String): FlagSet = {
+    flagName(index)(TERMindex) = name
+    FlagSet(TERMS | (1L << index))
+  }
+
+  /** The flag with given index between 2 and 63 which applies to types */
+  def typeFlag(index: Int, name: String): FlagSet = {
+    flagName(index)(TYPEindex) = name
+    FlagSet(TYPES | (1L << index))
+  }
+
+  /** The flag with given index between 2 and 63 which applies to both terms and types */
+  def commonFlag(index: Int, name: String): FlagSet =
+    termFlag(index, name) | typeFlag(index, name)
+
+  // Available flags:
+
   final val Empty = FlagSet(0)
 
+  final val Private = commonFlag(3, "private")
+  final val Accessor = termFlag(4, "<accessor>")
+
   final val Error = FlagSet(1 << 32)
   final val Frozen = FlagSet(???)
-  final val Private = FlagSet(???)
   final val Package = FlagSet(???)
 
 }
\ No newline at end of file