redundant_objc_attribute incorrectly flagging inner @objc enum

[JaviSoto]

The following code triggers redundant_objc_attribute:

@objcMembers 
class Foo {
  @objc enum Bar { }
}

The code to flag a redundant @objc should only trigger if the declaration is a member, not an inner type.

I'm gonna take a stab at fixing this myself.

[JaviSoto]

I tried to fix this like this:

diff --git a/Source/SwiftLintFramework/Rules/Idiomatic/RedundantObjcAttributeRule.swift b/Source/SwiftLintFramework/Rules/Idiomatic/RedundantObjcAttributeRule.swift
index 1eae87f4..bd82af14 100644
--- a/Source/SwiftLintFramework/Rules/Idiomatic/RedundantObjcAttributeRule.swift
+++ b/Source/SwiftLintFramework/Rules/Idiomatic/RedundantObjcAttributeRule.swift
@@ -38,6 +38,13 @@ public struct RedundantObjcAttributeRule: ASTRule, ConfigurationProviderRule, Au
             }
             """,
             """
+            @objcMembers
+            class Foo {
+              @objc
+              enum Bar { }
+            }
+            """,
+            """
             @objc
             extension Foo {
               var bar: Int {
@@ -142,9 +149,10 @@ public struct RedundantObjcAttributeRule: ASTRule, ConfigurationProviderRule, Au
                          dictionary: [String: SourceKitRepresentable]) -> [StyleViolation] {
         let enclosedSwiftAttributes = Set(dictionary.enclosedSwiftAttributes)
         guard let offset = dictionary.offset,
-              enclosedSwiftAttributes.contains(.objc),
-              !dictionary.isObjcAndIBDesignableDeclaredExtension else {
-            return []
+            enclosedSwiftAttributes.contains(.objc),
+            kind.inheritsObjFromObjCMembers,
+            !dictionary.isObjcAndIBDesignableDeclaredExtension else {
+                return []
         }

         let isInObjcVisibleScope = { () -> Bool in
@@ -167,6 +175,15 @@ public struct RedundantObjcAttributeRule: ASTRule, ConfigurationProviderRule, Au
     }
 }

+private extension SwiftDeclarationKind {
+    /// Whether `@objcMembers` in its parent type applies to this kind of declaration, making it implicitly `@objc`.
+    var inheritsObjFromObjCMembers: Bool {
+        let applicableKinds = SwiftDeclarationKind.variableKinds.union(SwiftDeclarationKind.functionKinds)
+
+        return applicableKinds.contains(self)
+    }
+}
+
 private extension Dictionary where Key == String, Value == SourceKitRepresentable {
     var objcAttributeLocationRanges: RedundantObjcAttributeRule.ObjcAttributeLocations {
         var objcImpliedAttributeLocatioRanges = RedundantObjcAttributeRule.ObjcAttributeLocations()

But this is not correct, because then this avoids flagging things like @objc @NSManaged class Foo.
However, while trying to understand how the implementation works, I discovered another fundamental issue with it, that unfortunately I don't have the time right now to try to fix. My recommendation is to, for the time being, make this rule not be enabled by default, since it has a couple of IMO big issues.

This other issue I was referring to is the following:

@objcMembers 
class Foo {
  class Bar: NSObject { 
    @objc foo: Any
  }
}

I think that the code is right now assuming that the whole range from class Foo { to the closing } of that class to objc visible scope. This is not correct, since @objcMembers doesn't apply to members of inner types.