Alternative fix

Author: Blaisorblade

compiler/src/dotty/tools/dotc/parsing/Parsers.scala

@@ -1975,11 +1975,24 @@ object Parsers {
     /** ImportSelector ::= id [`=>' id | `=>' `_']
      */
     def importSelector(): Tree = {
+      val start = in.offset
       val from = termIdentOrWildcard()
       if (from.name != nme.WILDCARD && in.token == ARROW)
         atPos(startOffset(from), in.skipToken()) {
-          Thicket(from, termIdentOrWildcard())
+          val start2 = in.offset
+          val to = termIdentOrWildcard()
+          val toWithPos =
+            if (to.name == nme.ERROR)
+              // error identifiers don't consume any characters, so atPos(start)(id) wouldn't set a position.
+              // Some testcases would then fail in Positioned.checkPos. Set a position anyway!
+              atPos(start2, start2, in.lastOffset)(to)
+            else
+              to
+          Thicket(from, toWithPos)
         }
+      else if (from.name == nme.ERROR) {
+        atPos(start, start, in.lastOffset)(from)
+      }
       else from
     }