Fix condition in checking if method is private in CHeckUnused

Author: szymon-rd

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

@@ -118,7 +118,7 @@ class CheckUnused private (phaseMode: CheckUnused.PhaseMode, suffix: String, _ke
 
   override def prepareForDefDef(tree: tpd.DefDef)(using Context): Context =
     unusedDataApply{ ud =>
-      if !tree.rawMods.is(Private) then
+      if !tree.symbol.is(Private) then
         tree.termParamss.flatten.foreach { p =>
           ud.addIgnoredParam(p.symbol)
         }

tests/neg-custom-args/fatal-warnings/i15503e.scala

@@ -8,7 +8,7 @@ object Foo {
   private def f2(a: Int) = default_val // error
   private def f3(a: Int)(using Int) = a // OK
   private def f4(a: Int)(using Int) = default_val // error
-  private def f6(a: Int)(using Int) = summon[Int] // ok
+  private def f6(a: Int)(using Int) = summon[Int] // error
   private def f7(a: Int)(using Int) = summon[Int] + a // OK
 }
 
@@ -49,7 +49,7 @@ package foo.test.trivial:
     private def f6(x: Int) = X // OK
     private def f7(x: Int) = Y // OK
     private def f8(x: Int): List[C] = Nil // OK
-    private def f9(x: Int): List[Int] = List(1,2,3,4) // ok
+    private def f9(x: Int): List[Int] = List(1,2,3,4) // error
     private def foo:Int = 32  // OK
     private def f77(x: Int) = foo // error
   }

tests/neg-custom-args/fatal-warnings/i15503f.scala

@@ -8,7 +8,7 @@ object Xd {
   private def f2(a: Int) = 1 // OK
   private def f3(a: Int)(using Int) = a // OK
   private def f4(a: Int)(using Int) = default_int // OK
-  private def f6(a: Int)(using Int) = summon[Int] // OK
+  private def f6(a: Int)(using Int) = summon[Int] // error
   private def f7(a: Int)(using Int) = summon[Int] + a // OK
   private def f8(a: Int)(using foo: Int) = a // error
 }

tests/neg-custom-args/fatal-warnings/i15503g.scala

@@ -8,7 +8,7 @@ object Foo {
   private def f2(a: Int) = default_int // error
   private def f3(a: Int)(using Int) = a // OK
   private def f4(a: Int)(using Int) = default_int // error
-  private def f6(a: Int)(using Int) = summon[Int] // ok
+  private def f6(a: Int)(using Int) = summon[Int] // error
   private def f7(a: Int)(using Int) = summon[Int] + a // OK
   /* --- Trivial method check --- */
   private def g1(x: Int) = 1 // OK