Re-enable tree checkers

My expectation is that tree checkers are re-typechecking the trees
and making sure they are consistent. Unfortunately, following
patch aced32d05c97651534f468bc9a475ea5f6ae75b8, the call to
clearType() was removed, thus the typer no longer recursed inside
the trees, rendering the type checkers framework useless.

This is an attempt to make the tree checkers run again, by resetting
the type of a tree before the call to super.typed, thus allowing the
typer to actually visit the entire tree (not just the outer package
definition).

The work was prompted by SI-9442, where the type checkers would
gladly allow validate the inconsistent trees.

1 files changed, 8 insertions, 1 deletions

diff --git a/src/compiler/scala/tools/nsc/typechecker/TreeCheckers.scala b/src/compiler/scala/tools/nsc/typechecker/TreeCheckers.scala
index a7d48ceb89..e8db8309f1 100644
--- a/src/compiler/scala/tools/nsc/typechecker/TreeCheckers.scala
+++ b/src/compiler/scala/tools/nsc/typechecker/TreeCheckers.scala
@@ -262,7 +262,14 @@ abstract class TreeCheckers extends Analyzer {
         checkedTyped(tree, mode, pt)
     )
     private def checkedTyped(tree: Tree, mode: Mode, pt: Type): Tree = {
-      val typed = wrap(tree)(super.typed(tree, mode, pt))
+      val typed = wrap(tree)(super.typed(tree.clearType(), mode, pt))
+
+      // Vlad: super.typed returns null for package defs, why is that?
+      if (typed eq null)
+        return tree
+
+      if (typed.tpe ne null)
+        assert(!typed.tpe.isErroneous, "Tree has erroneous type: " + typed)
 
       if (tree ne typed)
         treesDiffer(tree, typed)