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//===----------------------------------------------------------------------===//
//
// This source file is part of the Swift.org open source project
//
// Copyright (c) 2014 - 2023 Apple Inc. and the Swift project authors
// Licensed under Apache License v2.0 with Runtime Library Exception
//
// See https://swift.org/LICENSE.txt for license information
// See https://swift.org/CONTRIBUTORS.txt for the list of Swift project authors
//
//===----------------------------------------------------------------------===//
import SwiftDiagnostics
import SwiftSyntax
import SwiftSyntaxBuilder
import SwiftSyntaxMacros
public struct MetaEnumMacro {
let parentTypeName: TokenSyntax
let childCases: [EnumCaseElementSyntax]
let access: DeclModifierListSyntax.Element?
let parentParamName: TokenSyntax
init(node: AttributeSyntax, declaration: some DeclGroupSyntax, context: some MacroExpansionContext) throws {
guard let enumDecl = declaration.as(EnumDeclSyntax.self) else {
throw DiagnosticsError(diagnostics: [
CaseMacroDiagnostic.notAnEnum(declaration).diagnose(at: Syntax(node))
])
}
parentTypeName = enumDecl.name.with(\.trailingTrivia, [])
access = enumDecl.modifiers.first(where: \.isNeededAccessLevelModifier)
childCases = enumDecl.caseElements.map { parentCase in
parentCase.with(\.parameterClause, nil)
}
parentParamName = context.makeUniqueName("parent")
}
func makeMetaEnum() -> DeclSyntax {
// FIXME: Why does this need to be a string to make trailing trivia work properly?
let caseDecls =
childCases
.map { childCase in
" case \(childCase.name)"
}
.joined(separator: "\n")
return """
\(access)enum Meta {
\(raw: caseDecls)
\(makeMetaInit())
}
"""
}
func makeMetaInit() -> DeclSyntax {
// FIXME: Why does this need to be a string to make trailing trivia work properly?
let caseStatements =
childCases
.map { childCase in
"""
case .\(childCase.name):
self = .\(childCase.name)
"""
}
.joined(separator: "\n")
return """
\(access)init(_ \(parentParamName): \(parentTypeName)) {
switch \(parentParamName) {
\(raw: caseStatements)
}
}
"""
}
}
extension MetaEnumMacro: MemberMacro {
public static func expansion(
of node: AttributeSyntax,
providingMembersOf declaration: some DeclGroupSyntax,
in context: some MacroExpansionContext
) throws -> [DeclSyntax] {
let macro = try MetaEnumMacro(node: node, declaration: declaration, context: context)
return [macro.makeMetaEnum()]
}
}
extension EnumDeclSyntax {
var caseElements: [EnumCaseElementSyntax] {
memberBlock.members.flatMap { member in
guard let caseDecl = member.decl.as(EnumCaseDeclSyntax.self) else {
return Array<EnumCaseElementSyntax>()
}
return Array(caseDecl.elements)
}
}
}
enum CaseMacroDiagnostic {
case notAnEnum(DeclGroupSyntax)
}
extension CaseMacroDiagnostic: DiagnosticMessage {
var message: String {
switch self {
case .notAnEnum(let decl):
return "'@MetaEnum' can only be attached to an enum, not \(decl.descriptiveDeclKind(withArticle: true))"
}
}
var diagnosticID: MessageID {
switch self {
case .notAnEnum:
return MessageID(domain: "MetaEnumDiagnostic", id: "notAnEnum")
}
}
var severity: DiagnosticSeverity {
switch self {
case .notAnEnum:
return .error
}
}
func diagnose(at node: Syntax) -> Diagnostic {
Diagnostic(node: node, message: self)
}
}
extension DeclGroupSyntax {
func descriptiveDeclKind(withArticle article: Bool = false) -> String {
switch self {
case is ActorDeclSyntax:
return article ? "an actor" : "actor"
case is ClassDeclSyntax:
return article ? "a class" : "class"
case is ExtensionDeclSyntax:
return article ? "an extension" : "extension"
case is ProtocolDeclSyntax:
return article ? "a protocol" : "protocol"
case is StructDeclSyntax:
return article ? "a struct" : "struct"
case is EnumDeclSyntax:
return article ? "an enum" : "enum"
default:
fatalError("Unknown DeclGroupSyntax")
}
}
}
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