Backport "Fix WUnused for accessible symbols that are renamed" (#17277)

Backports #17177

Author: Kordyjan

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

@@ -603,11 +603,13 @@ 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 || sym.isRenamedSymbol(symName)) && sym.exists then
           selector.orElse(dealiasedSelector).orElse(wildcard) // selector with name or wildcard (or given)
         else
           None
 
+      private def isRenamedSymbol(symNameInScope: Option[Name])(using Context) =
+        sym.name != nme.NO_NAME && symNameInScope.exists(_.toSimpleName != sym.name.toSimpleName)
 
       private def dealias(symbol: Symbol)(using Context): Symbol =
         if(symbol.isType && symbol.asType.denot.isAliasType) then

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
+    }
+  }