Fix WUnused for accessible symbols that are renamed

Author: szymon-rd

compiler/src/dotty/tools/dotc/transform/CheckUnused.scala

@@ -603,7 +603,7 @@ object CheckUnused:
           case (sel, sym) if dealias(sym) == dealiasedSym => sel
         }.headOption else None
         def wildcard = sels.find(sel => sel.isWildcard && ((sym.is(Given) == sel.isGiven) || sym.is(Implicit)))
-        if qualHasSymbol && !isAccessible && sym.exists then
+        if qualHasSymbol && (!isAccessible || symName.exists(_ != sym.name)) && sym.exists then
           selector.orElse(dealiasedSelector).orElse(wildcard) // selector with name or wildcard (or given)
         else
           None

tests/neg-custom-args/fatal-warnings/i15503i.scala

@@ -287,3 +287,17 @@ package foo.test.i17156:
   package c:
     import b.Xd
     trait Z derives Xd
+
+package foo.test.i17117:
+  package example {
+    object test1 {
+      val test = "test"
+    }
+
+    object test2 {
+
+      import example.test1 as t1
+
+      val test = t1.test
+    }
+  }