1 files changed, 56 insertions, 0 deletions
diff --git a/src/dotty/tools/dotc/typer/ReTyper.scala b/src/dotty/tools/dotc/typer/ReTyper.scala
new file mode 100644
index 000000000..896dbba7d
--- /dev/null
+++ b/src/dotty/tools/dotc/typer/ReTyper.scala
@@ -0,0 +1,56 @@
+package dotty.tools.dotc
+package typer
+
+import core.Contexts._
+import core.Types._
+import core.Symbols.Symbol
+import typer.ProtoTypes._
+import ast.{tpd, untpd}
+import ast.Trees._
+
+/** A version of Typer that keeps all symbols defined and referenced in a
+ *  previously typed tree.
+ *
+ *  All definition nodes keep their symbols. All leaf nodes for idents, selects,
+ *  and TypeTrees keep their types. Indexing is a no-op.
+ *
+ *  Otherwise, everything is as in Typer.
+ */
+class ReTyper extends Typer {
+  import tpd._
+
+  protected def promote(tree: untpd.Tree)(implicit ctx: Context): tree.ThisTree[Type] = {
+    assert(tree.hasType)
+    tree.withType(tree.typeOpt)
+  }
+
+  override def typedIdent(tree: untpd.Ident, pt: Type)(implicit ctx: Context): Tree =
+    promote(tree)
+
+  override def typedSelect(tree: untpd.Select, pt: Type)(implicit ctx: Context): Tree = {
+    assert(tree.hasType)
+    val qual1 = typed(tree.qualifier, AnySelectionProto)
+    untpd.cpy.Select(tree, qual1, tree.name).withType(tree.typeOpt)
+  }
+
+  override def typedSelectFromTypeTree(tree: untpd.SelectFromTypeTree, pt: Type)(implicit ctx: Context): SelectFromTypeTree = {
+    assert(tree.hasType)
+    val qual1 = typed(tree.qualifier, AnySelectionProto)
+    untpd.cpy.SelectFromTypeTree(tree, qual1, tree.name).withType(tree.typeOpt)
+  }
+
+  override def typedTypeTree(tree: untpd.TypeTree, pt: Type)(implicit ctx: Context): TypeTree =
+    promote(tree)
+
+  override def typedBind(tree: untpd.Bind, pt: Type)(implicit ctx: Context): Bind = {
+    assert(tree.hasType)
+    val body1 = typed(tree.body, pt)
+    untpd.cpy.Bind(tree, tree.name, body1).withType(tree.typeOpt)
+  }
+
+  override def retrieveSym(tree: untpd.Tree)(implicit ctx: Context): Symbol = tree.symbol
+
+  override def localTyper(sym: Symbol) = this
+
+  override def index(trees: List[untpd.Tree])(implicit ctx: Context) = ctx
+}
+\ No newline at end of file