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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
//
//===----------------------------------------------------------------------===//
#if swift(>=6)
public import SwiftSyntax
#else
import SwiftSyntax
#endif
/// Describes a macro that can add members to the declaration it's attached to.
public protocol MemberMacro: AttachedMacro {
/// Expand an attached declaration macro to produce a set of members.
///
/// - Parameters:
/// - node: The custom attribute describing the attached macro.
/// - declaration: The declaration the macro attribute is attached to.
/// - context: The context in which to perform the macro expansion.
///
/// - Returns: the set of member declarations introduced by this macro, which
/// are nested inside the `attachedTo` declaration.
///
/// - Warning: This is the legacy `expansion` function of `MemberMacro` that is provided for backwards-compatiblity.
/// Use ``expansion(of:providingMembersOf:conformingTo:in:)-1sxoe`` instead.
static func expansion(
of node: AttributeSyntax,
providingMembersOf declaration: some DeclGroupSyntax,
in context: some MacroExpansionContext
) throws -> [DeclSyntax]
/// Expand an attached declaration macro to produce a set of members.
///
/// - Parameters:
/// - node: The custom attribute describing the attached macro.
/// - declaration: The declaration the macro attribute is attached to.
/// - conformingTo: The set of protocols that were declared
/// in the set of conformances for the macro and to which the declaration
/// does not explicitly conform. The member macro itself cannot declare
/// conformances to these protocols (only an extension macro can do that),
/// but can provide supporting declarations, such as a required
/// initializer or stored property, that cannot be written in an
/// extension.
/// - context: The context in which to perform the macro expansion.
///
/// - Returns: the set of member declarations introduced by this macro, which
/// are nested inside the `attachedTo` declaration.
static func expansion(
of node: AttributeSyntax,
providingMembersOf declaration: some DeclGroupSyntax,
conformingTo protocols: [TypeSyntax],
in context: some MacroExpansionContext
) throws -> [DeclSyntax]
}
private struct UnimplementedExpansionMethodError: Error, CustomStringConvertible {
var description: String {
"""
Types conforming to `MemberMacro` must implement either \
expansion(of:providingMembersOf:in:) or \
expansion(of:providingMembersOf:conformingTo:in:)
"""
}
}
extension MemberMacro {
/// Default implementation supplies no conformances.
public static func expansion(
of node: AttributeSyntax,
providingMembersOf declaration: some DeclGroupSyntax,
in context: some MacroExpansionContext
) throws -> [DeclSyntax] {
throw UnimplementedExpansionMethodError()
}
/// Default implementation that ignores the unhandled conformances.
public static func expansion(
of node: AttributeSyntax,
providingMembersOf declaration: some DeclGroupSyntax,
conformingTo protocols: [TypeSyntax],
in context: some MacroExpansionContext
) throws -> [DeclSyntax] {
return try expansion(of: node, providingMembersOf: declaration, in: context)
}
}
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