Equatable for Nuno

Sources_Equatable_Equatable.swift

// The Swift Programming Language
// https://docs.swift.org/swift-book

@attached(conformance)
public macro Equatable() = #externalMacro(
    module: "EquatableMacros",
    type: "EquatableMacro"
)

Sources_EquatableClient_main.swift

import Equatable

@Equatable
struct SomeStruct { }

let a = SomeStruct()
let b = SomeStruct()

print(a == b)

Sources_EquatableMacros_EquatableMacro.swift

import SwiftCompilerPlugin
import SwiftSyntax
import SwiftSyntaxBuilder
import SwiftSyntaxMacros

public struct EquatableMacro: ConformanceMacro {

    public static func expansion(
        of node: AttributeSyntax,
        providingConformancesOf decl: some DeclGroupSyntax,
        in context: some MacroExpansionContext
    ) throws -> [(TypeSyntax, GenericWhereClauseSyntax?)] {
        let protocolName: TypeSyntax = "Equatable"
        return [(protocolName, nil)]
    }

    enum Error: Swift.Error {
        case print(String)
        }
}

@main
struct EquatableMacroPlugin: CompilerPlugin {
    let providingMacros: [Macro.Type] = [
        EquatableMacro.self,
    ]
}

Tests_EquatableTests.swift

import SwiftSyntaxMacros
import SwiftSyntaxMacrosTestSupport
import XCTest
import EquatableMacros

let testMacros: [String: Macro.Type] = [
    "Equatable": EquatableMacro.self,
]

final class EquatableTests: XCTestCase {
    func testMacro() {
        assertMacroExpansion(
            """
            @Equatable____
            class XXX {}
            """,
            expandedSource: """
            """,
            macros: testMacros
        )
    }
}