SwiftLint/Source/SwiftLintBuiltInRules/Rules/Lint/ProhibitedInterfaceBuilderRule.swift

import SwiftSyntax

@SwiftSyntaxRule
struct ProhibitedInterfaceBuilderRule: OptInRule {
    var configuration = SeverityConfiguration<Self>(.warning)

    static let description = RuleDescription(
        identifier: "prohibited_interface_builder",
        name: "Prohibited Interface Builder",
        description: "Creating views using Interface Builder should be avoided",
        kind: .lint,
        nonTriggeringExamples: [
            wrapExample("var label: UILabel!"),
            wrapExample("@objc func buttonTapped(_ sender: UIButton) {}")
        ],
        triggeringExamples: [
            wrapExample("@IBOutlet ↓var label: UILabel!"),
            wrapExample("@IBAction ↓func buttonTapped(_ sender: UIButton) {}")
        ]
    )
}

private extension ProhibitedInterfaceBuilderRule {
    final class Visitor: ViolationsSyntaxVisitor<ConfigurationType> {
        override func visitPost(_ node: VariableDeclSyntax) {
            if node.isIBOutlet {
                violations.append(node.bindingSpecifier.positionAfterSkippingLeadingTrivia)
            }
        }

        override func visitPost(_ node: FunctionDeclSyntax) {
            if node.isIBAction {
                violations.append(node.funcKeyword.positionAfterSkippingLeadingTrivia)
            }
        }
    }
}

private func wrapExample(_ text: String, file: StaticString = #file, line: UInt = #line) -> Example {
    return Example("""
    class ViewController: UIViewController {
        \(text)
    }
    """, file: file, line: line)
}