Fix #12249: don't export java defined modules

Author: OlivierBlanvillain

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

@@ -1000,6 +1000,8 @@ class Namer { typer: Typer =>
           ) match
               case Some(other) => No(i"overrides ${other.showLocated}, which is already a member of $cls")
               case None => Yes
+        else if sym.isAllOf(JavaModule) then
+          Skip
         else Yes
       }
 

tests/neg/12249.scala

@@ -0,0 +1,9 @@
+
+export java.util.UUID
+
+def bar = println(new UUID(1, 2)) // OK
+
+def foo = println(UUID.randomUUID()) // error
+//                ^^^^
+//                Not found: UUID
+