Currently working Swift macro that deals with a dictionary (`DictionaryElementListSyntax`, `DictionaryExprSyntax`)

ExperimentMacro.swift

// Macro signature
@freestanding(declaration, names: arbitrary)
public macro ExperimentMacro(_ named: String, contains: [String: String]) = #externalMacro(module: "ExperimentMacroMacros", type: "ExperimentMacro")

ExperimentMacroMacro.swift

// Implementation
import SwiftCompilerPlugin
import SwiftSyntax
import SwiftSyntaxBuilder
import SwiftSyntaxMacros

public struct ExperimentMacro: DeclarationMacro {
    public static func expansion(
        of node: some FreestandingMacroExpansionSyntax,
        in context: some MacroExpansionContext
    ) throws -> [DeclSyntax] {

        guard let argument = node.argumentList.as(LabeledExprListSyntax.self),
              argument.count > 0 else {
            fatalError("No cases")
        }

        let string = argument
            .children(viewMode: .all)
            .compactMap { $0.as(LabeledExprSyntax.self) }
            .map(\.expression)
            .compactMap { $0.as(StringLiteralExprSyntax.self) }
            .map { String(describing: $0) }

        let dictArray = argument
            .children(viewMode: .all)
            .compactMap { $0.as(LabeledExprSyntax.self) }
            .map(\.expression)[1].cast(DictionaryExprSyntax.self).content
      
        return [
            """
            public let stringTesting: [String] = \(raw: string)
            public let dictTesting: String = \(literal: String(describing: dictArray))
            """
        ]
    }
}