Move Mode to core

Mode is used from a lot of low-level code, does not just reflect Typer info.
So it makes more sense top to place it in the core package.

1 files changed, 85 insertions, 0 deletions

diff --git a/src/dotty/tools/dotc/core/Mode.scala b/src/dotty/tools/dotc/core/Mode.scala
new file mode 100644
index 000000000..5b3dbc872
--- /dev/null
+++ b/src/dotty/tools/dotc/core/Mode.scala
@@ -0,0 +1,85 @@
+package dotty.tools.dotc.core
+
+/** A collection of mode bits that are part of a context */
+case class Mode(val bits: Int) extends AnyVal {
+  import Mode._
+  def | (that: Mode) = Mode(bits | that.bits)
+  def & (that: Mode) = Mode(bits & that.bits)
+  def &~ (that: Mode) = Mode(bits & ~that.bits)
+  def is (that: Mode) = (bits & that.bits) == that.bits
+
+  def isExpr = (this & PatternOrType) == None
+
+  override def toString =
+    (0 until 31).filter(i => (bits & (1 << i)) != 0).map(modeName).mkString("Mode(", ",", ")")
+}
+
+object Mode {
+  val None = Mode(0)
+
+  private val modeName = new Array[String](32)
+
+  def newMode(bit: Int, name: String): Mode = {
+    modeName(bit) = name
+    Mode(1 << bit)
+  }
+
+  val Pattern = newMode(0, "Pattern")
+  val Type = newMode(1, "Type")
+
+  val ImplicitsEnabled = newMode(2, "ImplicitsEnabled")
+  val InferringReturnType = newMode(3, "InferringReturnType")
+
+  /** This mode bit is set if we collect information without reference to a valid
+   *  context with typerstate and constraint. This is typically done when we
+   *  cache the eligibility of implicits. Caching needs to be done across different constraints.
+   *  Therefore, if TypevarsMissContext is set, subtyping becomes looser, and assumes
+   *  that PolyParams can be sub- and supertypes of anything. See TypeComparer.
+   */
+  val TypevarsMissContext = newMode(4, "TypevarsMissContext")
+  val CheckCyclic = newMode(5, "CheckCyclic")
+
+  val InSuperCall = newMode(6, "InSuperCall")
+
+  /** This mode bit is set if we want to allow accessing a symbol's denotation
+   *  at a period before that symbol is first valid. An example where this is
+   *  the case is if we want to examine the environment where an access is made.
+   *  The computation might take place at an earlier phase (e.g. it is part of
+   *  some completion such as unpickling), but the environment might contain
+   *  synbols that are not yet defined in that phase.
+   *  If the mode bit is set, getting the denotation of a symbol at a phase
+   *  before the symbol is defined will return the symbol's denotation at the
+   *  first phase where it is valid, instead of throwing a NotDefinedHere error.
+   */
+  val FutureDefsOK = newMode(7, "FutureDefsOK")
+
+  /** Allow GADTFlexType labelled types to have their bounds adjusted */
+  val GADTflexible = newMode(8, "GADTflexible")
+
+  /** Allow dependent functions. This is currently necessary for unpickling, because
+   *  some dependent functions are passed through from the front end(s?), even though they
+   *  are technically speaking illegal.
+   */
+  val AllowDependentFunctions = newMode(9, "AllowDependentFunctions")
+
+  /** We are currently printing something: avoid to produce more logs about
+   *  the printing
+   */
+  val Printing = newMode(10, "Printing")
+
+  /** We are currently typechecking an ident to determine whether some implicit
+   *  is shadowed - don't do any other shadowing tests.
+   */
+  val ImplicitShadowing = newMode(11, "ImplicitShadowing")
+
+  /** We are currently in a `viewExists` check. In that case, ambiguous
+   *  implicits checks are disabled and we succeed with the first implicit
+   *  found.
+   */
+  val ImplicitExploration = newMode(12, "ImplicitExploration")
+
+  /** We are currently unpickling Scala2 info */
+  val Scala2Unpickling = newMode(13, "Scala2Unpickling")
+
+  val PatternOrType = Pattern | Type
+}