More accurate or postcondition conchecking in TreeChecker

Previous postcondition checking did not take into account that phases are
not flat - they consist in part of macro phases that contain miniphases.
In fact the whole set up in Run is dubiuos - we should eliminate the problem at the
root, as described in the TODO in run.

1 files changed, 13 insertions, 1 deletions

diff --git a/src/dotty/tools/dotc/transform/TreeChecker.scala b/src/dotty/tools/dotc/transform/TreeChecker.scala
index 6d6a88e36..cf32df61b 100644
--- a/src/dotty/tools/dotc/transform/TreeChecker.scala
+++ b/src/dotty/tools/dotc/transform/TreeChecker.scala
@@ -35,11 +35,23 @@ import java.lang.AssertionError
 class TreeChecker {
   import ast.tpd._
 
+  private def previousPhases(phases: List[Phase])(implicit ctx: Context): List[Phase] = phases match {
+    case (phase: TreeTransformer) :: phases1 =>
+      val subPhases = phase.transformations.map(_.phase)
+      val previousSubPhases = previousPhases(subPhases.toList)
+      if (previousSubPhases.length == subPhases.length) previousSubPhases ::: previousPhases(phases1)
+      else previousSubPhases
+    case phase :: phases1 if phase ne ctx.phase =>
+      phase :: previousPhases(phases1)
+    case _ =>
+      Nil
+  }
+
   def check(phasesToRun: Seq[Phase], ctx: Context) = {
     println(s"checking ${ctx.compilationUnit} after phase ${ctx.phase.prev}")
     val checkingCtx = ctx.fresh
       .setTyperState(ctx.typerState.withReporter(new ThrowingReporter(ctx.typerState.reporter)))
-    val checker = new Checker(phasesToRun.takeWhile(_ ne ctx.phase))
+    val checker = new Checker(previousPhases(phasesToRun.toList)(ctx))
     checker.typedExpr(ctx.compilationUnit.tpdTree)(checkingCtx)
   }