Survive untyped trees in eta expansion

Untyped trees may appear in programs that already had some errors reported.

Author: odersky

compiler/src/dotty/tools/dotc/ast/tpd.scala

@@ -1004,7 +1004,7 @@ object tpd extends Trees.Instance[Type] with TypedTreeInfo {
   def sameTypes(trees: List[tpd.Tree], trees1: List[tpd.Tree]): Boolean = {
     if (trees.isEmpty) trees.isEmpty
     else if (trees1.isEmpty) trees.isEmpty
-    else (trees.head.tpe eq trees1.head.tpe) && sameTypes(trees.tail, trees1.tail)
+    else (trees.head.typeOpt eq trees1.head.typeOpt) && sameTypes(trees.tail, trees1.tail)
   }
 
   def evalOnce(tree: Tree)(within: Tree => Tree)(implicit ctx: Context) = {

compiler/src/dotty/tools/dotc/typer/EtaExpansion.scala

@@ -43,7 +43,7 @@ abstract class Lifter {
   protected def liftedDef(sym: TermSymbol, rhs: Tree)(implicit ctx: Context): MemberDef = ValDef(sym, rhs)
 
   private def lift(defs: mutable.ListBuffer[Tree], expr: Tree, prefix: TermName = EmptyTermName)(implicit ctx: Context): Tree =
-    if (noLift(expr)) expr
+    if (noLift(expr) || !expr.hasType && ctx.reporter.errorsReported) expr
     else {
       val name = UniqueName.fresh(prefix)
       var liftedType = fullyDefinedType(expr.tpe.widen, "lifted expression", expr.pos)

tests/neg/parser-stability-6.scala

@@ -0,0 +1,2 @@
+class x0 {
+1 + x1 * / |= 2  // error // error