Generalize phase postcondition checking.

Have a general way how a phase can establish a postcondition which will be
checked each time a later phase is tree-checked.

Moves erasure constraints from TreeChecker to Erasure's post condition.

1 files changed, 7 insertions, 1 deletions

diff --git a/src/dotty/tools/dotc/core/Phases.scala b/src/dotty/tools/dotc/core/Phases.scala
index 6baec3cf6..27b7cd77d 100644
--- a/src/dotty/tools/dotc/core/Phases.scala
+++ b/src/dotty/tools/dotc/core/Phases.scala
@@ -12,6 +12,7 @@ import dotty.tools.dotc.transform.TreeTransforms.{TreeTransformer, MiniPhase, Tr
 import dotty.tools.dotc.transform.TreeTransforms
 import Periods._
 import typer.{FrontEnd, RefChecks}
+import ast.tpd
 import dotty.tools.dotc.transform.{Erasure, Flatten}
 
 trait Phases {
@@ -191,7 +192,12 @@ object Phases {
 
     def description: String = phaseName
 
-    def checkable: Boolean = true
+    /** Output should be checkable by TreeChecker */
+    def isCheckable: Boolean = true
+
+    /** Check what the phase achieves, to be called at any point after it is finished.
+     */
+    def checkPostCondition(tree: tpd.Tree)(implicit ctx: Context): Unit = ()
 
     def exists: Boolean = true