Fix #2856 Drop special treatment of packages in findRef

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

@@ -251,9 +251,16 @@ class Typer extends Namer with TypeAssigner with Applications with Implicits wit
           // context immediately nested in it. But for package contexts, it's
           // the opposite: the last context before the package changes. This distinction
           // is made so that top-level imports following a package clause are
-          // logically nested in that package clause.
+          // logically nested in that package clause. Finally, for the root package
+          // we switch back to the original test. This means that rop-level packages in
+          // the root package take priority over root imports. For instance,
+          // a top-level io package takes priority over scala.io.
+          // It would be nice if we could drop all this complication, and
+          // always use the second condition. Unfortunately compileStdLib breaks
+          // with an error on CI which I cannot replicate locally (not even
+          // with the exact list of files given).
           val isNewDefScope =
-            if (curOwner is Package) curOwner ne ctx.outer.owner
+            if (curOwner.is(Package) && !curOwner.isRoot) curOwner ne ctx.outer.owner
             else (ctx.scope ne lastCtx.scope) || (curOwner ne lastCtx.owner)
 
           if (isNewDefScope) {

tests/neg/i1641.scala

@@ -2,7 +2,7 @@ package bar { object bippy extends (Double => String) { def apply(x: Double): St
 package object println { def bippy(x: Int, y: Int, z: Int) = "(Int, Int, Int)" }
 object Test {
   def main(args: Array[String]): Unit = {
-    println(bar.bippy(5.5))
+    println(bar.bippy(5.5)) // error
     println(bar.bippy(1, 2, 3)) // error
   }
 }

tests/pos/i2856.scala

@@ -0,0 +1,7 @@
+package io.grpc {
+  trait Grpc
+}
+package bar {
+  import io.grpc.Grpc
+  object a extends Grpc
+}