Don't explicitly check for error trees in export selectors

[Cherry-picked 6e28679]

Author: KacperFKorban

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

@@ -1111,7 +1111,7 @@ class Namer { typer: Typer =>
     private def exportForwarders(exp: Export, pathMethod: Symbol)(using Context): List[tpd.MemberDef] =
       val buf = new mutable.ListBuffer[tpd.MemberDef]
       val Export(expr, selectors) = exp
-      if expr.isEmpty || selectors.exists(_.imported.name == nme.ERROR) then
+      if expr.isEmpty then
         report.error(em"Export selector must have prefix and `.`", exp.srcPos)
         return Nil
 

tests/neg/i20511.check

@@ -6,7 +6,9 @@
 8 |val i = 1 // error
   |^^^
   |'.' expected, but 'end of statement' found
--- Error: tests/neg/i20511.scala:7:21 ----------------------------------------------------------------------------------
+-- [E083] Type Error: tests/neg/i20511.scala:7:21 ----------------------------------------------------------------------
 7 |export toppingPrice, crustPrice // error // error
   |                     ^^^^^^^^^^
-  |                     Export selector must have prefix and `.`
+  |                     Any is not a valid export prefix, since it is not an immutable path
+  |
+  | longer explanation available when compiling with `-explain`