Swiftlint: valid_ibinspectable requires explicit types

[Igor-Palaguta]

New Issue Checklist

• [x] Updated SwiftLint to the latest version
• [x] I searched for existing GitHub issues

Describe the bug

valid_ibinspectable requires explicit types.

Swiftlint fires warning here:
@IBInspectable public var isSimulatingBarButtonItem = false

Complete output when running SwiftLint, including the stack trace and command used

$ swiftlint lint

warning: Valid IBInspectable Violation: @IBInspectable should be applied to variables only, have its type explicit and be of a supported type (valid_ibinspectable)

Environment

• SwiftLint version (run swiftlint version to be sure)?
  0.32.0

• Installation method used (Homebrew, CocoaPods, building from source, etc)?
  Via package file from releases assets

• Are you using nested configurations? no

• Which Xcode version are you using (check xcode-select -p)? Version 10.2.1 (10E1001)

// This triggers a violation:
import UIKit

public final class CloseButton: UIButton {
    @IBInspectable public var isSimulatingBarButtonItem = false
}

[Igor-Palaguta]

Interface Builder requires to add type explicitly in other case this property is not displayed as custom attribute.

[akovalov]

Adding public like @IBInspectable public var cornerRadius: CGFloat or public extension UIView { solved warning for me