swift-mirror/test/attr/diagnose_peer_macro.swift

// REQUIRES: swift_swift_parser, executable_test

// RUN: %empty-directory(%t)
// RUN: split-file %s %t

// Build the macro library
// RUN: %host-build-swift -swift-version 5 -emit-library -o %t/%target-library-name(MacroDefinition) -module-name=MacroDefinition %t/macro.swift

// Type check and verify
// RUN: %target-swift-frontend -typecheck -verify -load-plugin-library %t/%target-library-name(MacroDefinition) %t/test.swift

// This test verifies that @diagnose on a declaration does NOT propagate to peer
// declarations generated by an attached peer macro, because peers are
// independent siblings, not children of the annotated declaration's scope.

//--- macro.swift
import SwiftSyntax
import SwiftSyntaxMacros

public struct AddCompanionMacro: PeerMacro {
  public static func expansion(
    of node: AttributeSyntax,
    providingPeersOf declaration: some DeclSyntaxProtocol,
    in context: some MacroExpansionContext
  ) throws -> [DeclSyntax] {
    return [
      """
      func companion() -> String {
        return bar()
      }
      """
    ]
  }
}

/// A companion function with its own @diagnose.
public struct AddSuppressedCompanionMacro: PeerMacro {
  public static func expansion(
    of node: AttributeSyntax,
    providingPeersOf declaration: some DeclSyntaxProtocol,
    in context: some MacroExpansionContext
  ) throws -> [DeclSyntax] {
    return [
      """
      @diagnose(DeprecatedDeclaration, as: ignored)
      func suppressed() -> String {
        return bar()
      }
      """
    ]
  }
}

//--- test.swift

@available(*, deprecated)
func bar() -> String { return "GoodBye" }

@attached(peer, names: named(companion))
macro AddCompanion() = #externalMacro(module: "MacroDefinition", type: "AddCompanionMacro")

@attached(peer, names: named(suppressed))
macro AddSuppressedCompanion() = #externalMacro(module: "MacroDefinition", type: "AddSuppressedCompanionMacro")

struct TestPeerMacro {
  @diagnose(DeprecatedDeclaration, as: ignored)
  @AddCompanion // expected-note {{in expansion of macro 'AddCompanion' on instance method 'original()' here}}
  func original() -> String {
    return bar() // no warning — suppressed by @diagnose on this declaration
  }
  // expected-warning@@__swiftmacro_4test13TestPeerMacroV8original12AddCompanionfMp_.swift:2:10{{'bar()' is deprecated}}
}

struct TestPeerMacroSuppressed {
  @AddSuppressedCompanion
  func another() -> String {
    return bar() // expected-warning {{'bar()' is deprecated}}
  }
}