Create RetypingTreeMap that propagates types

If some node in tree is transformed changing the type,
the outer node could potentially also change type.

This patch implements a RetypingTreeMap that propagates those
changes until types converge. Propagation is done for tree nodes
that are able to compute their type based on their children:
Pair, Block, If, Match, CaseDef, Try, SeqLiteral, Annotated, Select.

1 files changed, 4 insertions, 9 deletions

diff --git a/src/dotty/tools/dotc/transform/TypeUtils.scala b/src/dotty/tools/dotc/transform/TypeUtils.scala
index f11bb980a..a26660092 100644
--- a/src/dotty/tools/dotc/transform/TypeUtils.scala
+++ b/src/dotty/tools/dotc/transform/TypeUtils.scala
@@ -1,23 +1,18 @@
 package dotty.tools.dotc
 package transform
 
-import core._
-import Types._
-import Contexts._
-import Symbols._
-import Decorators._
-import StdNames.nme
-import NameOps._
-import language.implicitConversions
+import dotty.tools.dotc.core.Types._
+
+import scala.language.implicitConversions
 
 object TypeUtils {
   implicit def decorateTypeUtils(tpe: Type): TypeUtils = new TypeUtils(tpe)
+
 }
 
 /** A decorator that provides methods for type transformations
  *  that are needed in the transofmer pipeline (not needed right now)
  */
 class TypeUtils(val self: Type) extends AnyVal {
-  import TypeUtils._
 
 }
\ No newline at end of file