声明名称不被 Swift 宏覆盖

Question

我正在摆弄新的 Swift 5.9 宏。

我有以下宏：

鉴于以下枚举

@associatedValues
enum Fruit {
    case banana(Banana)
    case grape(Grape)
}

我想

@associatedValues
enum Fruit {
    case banana(Banana)
    case grape(Grape)

    var bananaValue: Banana? { if ... return ... } }
    var grapeValue: Grape? { if ... return ... } }
}

我的实现是这样的：

public static func expansion<Declaration, Context>(
        of node: SwiftSyntax.AttributeSyntax,
        providingMembersOf declaration: Declaration,
        in context: Context
    ) throws -> [SwiftSyntax.DeclSyntax]
    where Declaration: SwiftSyntax.DeclGroupSyntax,
          Context: SwiftSyntaxMacros.MacroExpansionContext
    {
        
        guard let enumDeclaration = declaration.as(EnumDeclSyntax.self) else {
            throw AssociatedValuesMacroError.onlyApplicableToEnum
        }
        
        return enumDeclaration.memberBlock.members
            .compactMap { $0.decl.as(EnumCaseDeclSyntax.self) }
            .map { (_case: EnumCaseDeclSyntax) in

                let _element: EnumCaseElementListSyntax.Element = _case.elements.first!
                let caseName = _element.identifier
                let typeName = _element.associatedValue!.parameterList.first!.description

                return
                    """
                    var \(raw: caseName)Value: \(raw: typeName)? {
                        if case let .\(raw: caseName)(value) = self {
                            return value
                        } else {
                            return nil
                        }
                    }
                    """
            }
    }

现在，自动完成功能检测到新属性，但编译器告诉我：

Declaration name 'bananaValue' is not covered by macro 'associatedValues'

Declaration name 'grapeValue' is not covered by macro 'associatedValues'

测试会运行并验证输出，但不会在编译时验证。

我缺少什么？谢谢

Answer 1

我们需要添加names: arbitrary宏观作用。

@attached(member, names: arbitrary)
public macro AssociatedValues() = #externalMacro(module: "MyMacrosModule", type: "AssociatedValuesMacro")

注意：就我而言，我需要任意名称，因为名称是动态的。但如果您确实知道要添加哪些属性，则应该使用names: myCustomName。

另外，虽然不是特定问题的答案，但请确保将宏类型添加到CompilerPlugin.

#if canImport(SwiftCompilerPlugin)
import SwiftCompilerPlugin
import SwiftSyntaxMacros

@main
struct MacrosPlugin: CompilerPlugin {
  let providingMacros: [Macro.Type] = [
      AssociatedValueMacro.self
  ]
}