Allow trees to get error types in IDE even if

no errors were reported.

Author: odersky

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

@@ -115,7 +115,7 @@ object Trees {
      */
     def withType(tpe: Type)(implicit ctx: Context): ThisTree[Type] = {
       if (tpe.isInstanceOf[ErrorType])
-        assert(ctx.reporter.errorsReported)
+        assert(ctx.mode.is(Mode.Interactive) || ctx.reporter.errorsReported)
       else if (Config.checkTreesConsistent)
         checkChildrenTyped(productIterator)
       withTypeUnchecked(tpe)