[J2KT] Fix visibility translation of protected methods overriding protected methods which are translated as public.

These overrides are currently translated as `protected`, but should also be translated as `public`.

PiperOrigin-RevId: 926042301

Author: Googler

transpiler/java/com/google/j2cl/transpiler/backend/kotlin/MemberDescriptorUtils.kt

@@ -46,7 +46,17 @@ internal val MemberDescriptor.ktVisibility: KtVisibility
       isConstructor && hasInjectAnnotation -> KtVisibility.PUBLIC
       // When not translating actual visibilites, map protected to public, to allow access within
       // the same package across different types.
-      !useActualKtVisibility && visibility.isProtected -> KtVisibility.PUBLIC
+      isProtectedTranslatedAsPublic -> KtVisibility.PUBLIC
+      // Overrides of protected methods translated as public needs to be public.
+      this is MethodDescriptor && overridesProtectedAsPublic -> KtVisibility.PUBLIC
       // For all other cases, use the default visibility mapping.
       else -> KtVisibility.from(visibility)
     }
+
+internal val MemberDescriptor.isProtectedTranslatedAsPublic: Boolean
+  get() = !useActualKtVisibility && visibility.isProtected
+
+internal val MethodDescriptor.overridesProtectedAsPublic: Boolean
+  get() = javaOverriddenMethodDescriptors.any {
+    it.isProtectedTranslatedAsPublic || it.overridesProtectedAsPublic
+  }

transpiler/javatests/com/google/j2cl/readable/java/j2kt/VisibilityModifiers.java

@@ -58,12 +58,11 @@ protected void protectedMethod() {}
     private void privateMethod() {}
   }
 
-  // TODO(b/519538678): Uncomment when fixed.
-  // public static class ProtectedOverrideOfVisibilityWarningsSuppressed
-  //     extends VisibilityWarningsSuppressed.Public {
-  //   @Override
-  //   protected void protectedMethod() {}
-  // }
+  public static class ProtectedOverrideOfVisibilityWarningsSuppressed
+      extends VisibilityWarningsSuppressed.Public {
+    @Override
+    protected void protectedMethod() {}
+  }
 
   @AutoValue
   abstract static class Value {

transpiler/javatests/com/google/j2cl/readable/java/j2kt/output_kt/VisibilityModifiers.kt.txt

@@ -64,6 +64,10 @@ class VisibilityModifiers {
   private fun privateMethod() {}
  }
 
+ open class ProtectedOverrideOfVisibilityWarningsSuppressed: j2kt.VisibilityModifiers.VisibilityWarningsSuppressed.Public() {
+  override fun protectedMethod() {}
+ }
+ 
  @WasAutoValue
  internal abstract class Value {
   @javaemul.lang.annotations.WasAutoValue.Builder