Allow more leniency in time travel.

Makes the method pioneered in elidablePrefix more general. Also applies
it to accessWithin.

1 files changed, 12 insertions, 0 deletions

diff --git a/src/dotty/tools/dotc/typer/Mode.scala b/src/dotty/tools/dotc/typer/Mode.scala
index 417d461e1..eb911987b 100644
--- a/src/dotty/tools/dotc/typer/Mode.scala
+++ b/src/dotty/tools/dotc/typer/Mode.scala
@@ -34,5 +34,17 @@ object Mode {
   val TypevarsMissContext = newMode(4, "TypevarsMissContext")
   val CheckCyclic = newMode(5, "CheckCyclic")
 
+  /** 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(6, "FutureDefsOK")
+
   val PatternOrType = Pattern | Type
 }
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