[SE-0407] [Macros] Provide member macros with information about "missing" conformances

CHANGELOG.md

@@ -2,6 +2,18 @@
 
 _**Note:** This is in reverse chronological order, so newer entries are added to the top._
 
+## Swift 5.9.2
+
+* [SE-0407][]:
+
+  Member macros can specify a list of protocols via the `conformances` argument to the macro role. The macro implementation will be provided with those protocols that are listed but have not already been implemented by the type to which the member macro is attached, in the same manner as extension macros.
+
+   ```swift
+   @attached(member, conformances: Decodable, Encodable, names: named(init(from:), encode(to:)))
+@attached(extension, conformances: Decodable, Encodable, names: named(init(from:), encode(to:)))
+macro Codable() = #externalMacro(module: "MyMacros", type: "CodableMacro")
+   ```
+
 ## Swift 5.9
 
 * [SE-0382][], [SE-0389][], [SE-0394][], [SE-0397][]:
@@ -9830,6 +9842,7 @@ using the `.dynamicType` member to retrieve the type of an expression should mig
 [SE-0389]: https://github.com/apple/swift-evolution/blob/main/proposals/0389-attached-macros.md
 [SE-0394]: https://github.com/apple/swift-evolution/blob/main/proposals/0394-swiftpm-expression-macros.md
 [SE-0397]: https://github.com/apple/swift-evolution/blob/main/proposals/0397-freestanding-declaration-macros.md
+[SE-0407]: https://github.com/apple/swift-evolution/blob/main/proposals/0407-member-macro-conformances.md
 [#64927]: <https://github.com/apple/swift/issues/64927>
 [#42697]: <https://github.com/apple/swift/issues/42697>
 [#42728]: <https://github.com/apple/swift/issues/42728>

include/swift/AST/Decl.h

@@ -8621,6 +8621,7 @@ class MacroDecl : public GenericContext, public ValueDecl {
   /// be added if this macro does not contain an extension role.
   void getIntroducedConformances(
       NominalTypeDecl *attachedTo,
+      MacroRole role,
       SmallVectorImpl<ProtocolDecl *> &conformances) const;
 
   /// Returns a DeclName that represents arbitrary names.

include/swift/AST/TypeCheckRequests.h

@@ -3337,10 +3337,10 @@ class ResolveMacroRequest
   void noteCycleStep(DiagnosticEngine &diags) const;
 };
 
-/// Returns the resolved constraint types that an extension macro
-/// adds conformances to.
-class ResolveExtensionMacroConformances
-    : public SimpleRequest<ResolveExtensionMacroConformances,
+/// Returns the resolved constraint types that a macro references conformances
+/// to.
+class ResolveMacroConformances
+    : public SimpleRequest<ResolveMacroConformances,
                            ArrayRef<Type>(const MacroRoleAttr *, const Decl *),
                            RequestFlags::Cached> {
 public:

include/swift/AST/TypeCheckerTypeIDZone.def

@@ -360,7 +360,7 @@ SWIFT_REQUEST(TypeChecker, ResolveImplicitMemberRequest,
 SWIFT_REQUEST(TypeChecker, ResolveMacroRequest,
               ConcreteDeclRef(UnresolvedMacroReference, const Decl *),
               Cached, NoLocationInfo)
-SWIFT_REQUEST(TypeChecker, ResolveExtensionMacroConformances,
+SWIFT_REQUEST(TypeChecker, ResolveMacroConformances,
               ArrayRef<Type>(const MacroRoleAttr *, const Decl *),
               Cached, NoLocationInfo)
 SWIFT_REQUEST(TypeChecker, ResolveTypeEraserTypeRequest,

lib/AST/Attr.cpp

@@ -1387,7 +1387,7 @@ bool DeclAttribute::printImpl(ASTPrinter &Printer, const PrintOptions &Options,
     // Print conformances, if present.
     auto conformances = evaluateOrDefault(
         D->getASTContext().evaluator,
-        ResolveExtensionMacroConformances{Attr, D},
+        ResolveMacroConformances{Attr, D},
         {});
     if (!conformances.empty()) {
       Printer << ", conformances: ";

lib/AST/ConformanceLookupTable.cpp

@@ -503,7 +503,8 @@ void ConformanceLookupTable::addMacroGeneratedProtocols(
       MacroRole::Extension,
       [&](CustomAttr *attr, MacroDecl *macro) {
         SmallVector<ProtocolDecl *, 2> conformances;
-        macro->getIntroducedConformances(nominal, conformances);
+        macro->getIntroducedConformances(
+            nominal, MacroRole::Extension, conformances);
 
         for (auto *protocol : conformances) {
           addProtocol(protocol, attr->getLocation(), source);

lib/AST/Decl.cpp

@@ -10826,15 +10826,16 @@ void MacroDecl::getIntroducedNames(MacroRole role, ValueDecl *attachedTo,
 
 void MacroDecl::getIntroducedConformances(
     NominalTypeDecl *attachedTo,
+    MacroRole role,
     SmallVectorImpl<ProtocolDecl *> &conformances) const {
-  auto *attr = getMacroRoleAttr(MacroRole::Extension);
+  auto *attr = getMacroRoleAttr(role);
   if (!attr)
     return;
 
   auto &ctx = getASTContext();
   auto constraintTypes = evaluateOrDefault(
       ctx.evaluator,
-      ResolveExtensionMacroConformances{attr, this},
+      ResolveMacroConformances{attr, this},
       {});
 
   for (auto constraint : constraintTypes) {

lib/Sema/TypeCheckAttr.cpp

@@ -7151,7 +7151,7 @@ void AttributeChecker::visitMacroRoleAttr(MacroRoleAttr *attr) {
 
   (void)evaluateOrDefault(
       Ctx.evaluator,
-      ResolveExtensionMacroConformances{attr, D},
+      ResolveMacroConformances{attr, D},
       {});
 }
 

lib/Sema/TypeCheckMacros.cpp

@@ -1533,12 +1533,56 @@ swift::expandAttributes(CustomAttr *attr, MacroDecl *macro, Decl *member) {
   return macroSourceFile->getBufferID();
 }
 
+// Collect the protocol conformances that the macro asked about but were
+// not already present on the declaration.
+static TinyPtrVector<ProtocolDecl *> getIntroducedConformances(
+    NominalTypeDecl *nominal, MacroRole role, MacroDecl *macro,
+    SmallVectorImpl<ProtocolDecl *> *potentialConformances = nullptr) {
+  SmallVector<ProtocolDecl *, 2> potentialConformancesBuffer;
+  if (!potentialConformances)
+    potentialConformances = &potentialConformancesBuffer;
+  macro->getIntroducedConformances(nominal, role, *potentialConformances);
+
+  TinyPtrVector<ProtocolDecl *> introducedConformances;
+  for (auto protocol : *potentialConformances) {
+    SmallVector<ProtocolConformance *, 2> existingConformances;
+    nominal->lookupConformance(protocol, existingConformances);
+
+    bool hasExistingConformance = llvm::any_of(
+        existingConformances,
+        [&](ProtocolConformance *conformance) {
+          return conformance->getSourceKind() !=
+              ConformanceEntryKind::PreMacroExpansion;
+        });
+
+    if (!hasExistingConformance) {
+      introducedConformances.push_back(protocol);
+    }
+  }
+
+  return introducedConformances;
+}
+
 llvm::Optional<unsigned> swift::expandMembers(CustomAttr *attr,
                                               MacroDecl *macro, Decl *decl) {
+  auto nominal = dyn_cast<NominalTypeDecl>(decl);
+  if (!nominal) {
+    auto ext = dyn_cast<ExtensionDecl>(decl);
+    if (!ext)
+      return llvm::None;
+
+    nominal = ext->getExtendedNominal();
+    if (!nominal)
+      return llvm::None;
+  }
+  auto introducedConformances = getIntroducedConformances(
+      nominal, MacroRole::Member, macro);
+
   // Evaluate the macro.
   auto macroSourceFile =
       ::evaluateAttachedMacro(macro, decl, attr,
-                              /*passParentContext=*/false, MacroRole::Member);
+                              /*passParentContext=*/false, MacroRole::Member,
+                              introducedConformances);
   if (!macroSourceFile)
     return llvm::None;
 
@@ -1611,22 +1655,9 @@ llvm::Optional<unsigned> swift::expandExtensions(CustomAttr *attr,
     return llvm::None;
   }
 
-  // Collect the protocol conformances that the macro can add. The
-  // macro should not add conformances that are already stated in
-  // the original source.
-
   SmallVector<ProtocolDecl *, 2> potentialConformances;
-  macro->getIntroducedConformances(nominal, potentialConformances);
-
-  SmallVector<ProtocolDecl *, 2> introducedConformances;
-  for (auto protocol : potentialConformances) {
-    SmallVector<ProtocolConformance *, 2> existingConformances;
-    nominal->lookupConformance(protocol, existingConformances);
-    if (existingConformances.empty()) {
-      introducedConformances.push_back(protocol);
-    }
-  }
-
+  auto introducedConformances = getIntroducedConformances(
+      nominal, MacroRole::Extension, macro, &potentialConformances);
   auto macroSourceFile = ::evaluateAttachedMacro(macro, nominal, attr,
                                                  /*passParentContext=*/false,
                                                  role, introducedConformances);
@@ -1815,9 +1846,9 @@ ConcreteDeclRef ResolveMacroRequest::evaluate(Evaluator &evaluator,
 }
 
 ArrayRef<Type>
-ResolveExtensionMacroConformances::evaluate(Evaluator &evaluator,
-                                            const MacroRoleAttr *attr,
-                                            const Decl *decl) const {
+ResolveMacroConformances::evaluate(Evaluator &evaluator,
+                                   const MacroRoleAttr *attr,
+                                   const Decl *decl) const {
   auto *dc = decl->getDeclContext();
   auto &ctx = dc->getASTContext();
 

test/Macros/Inputs/syntax_macro_definitions.swift

@@ -2018,3 +2018,53 @@ public struct InitWithProjectedValueWrapperMacro: PeerMacro {
     ]
   }
 }
+
+public struct RequiredDefaultInitMacro: ExtensionMacro {
+  public static func expansion(
+    of node: AttributeSyntax,
+    attachedTo decl: some DeclGroupSyntax,
+    providingExtensionsOf type: some TypeSyntaxProtocol,
+    conformingTo protocols: [TypeSyntax],
+    in context: some MacroExpansionContext
+  ) throws -> [ExtensionDeclSyntax] {
+    if protocols.isEmpty {
+      return []
+    }
+
+    let decl: DeclSyntax =
+      """
+      extension \(type.trimmed): DefaultInit {
+      }
+
+      """
+
+    return [
+      decl.cast(ExtensionDeclSyntax.self)
+    ]
+  }
+}
+
+extension RequiredDefaultInitMacro: MemberMacro {
+  public static func expansion(
+    of node: AttributeSyntax,
+    providingMembersOf declaration: some DeclGroupSyntax,
+    in context: some MacroExpansionContext
+  ) throws -> [DeclSyntax] {
+    fatalError("old swift-syntax")
+  }
+
+  public static func expansion(
+    of node: AttributeSyntax,
+    providingMembersOf declaration: some DeclGroupSyntax,
+    conformingTo protocols: [TypeSyntax],
+    in context: some MacroExpansionContext
+  ) throws -> [DeclSyntax] {
+    let decl: DeclSyntax
+    if declaration.is(ClassDeclSyntax.self) && protocols.isEmpty {
+      decl = "required init() { }"
+    } else {
+      decl = "init() { }"
+    }
+    return [ decl ]
+  }
+}

test/Macros/macro_expand_member_with_conformances.swift

@@ -0,0 +1,22 @@
+// REQUIRES: swift_swift_parser
+
+// RUN: %empty-directory(%t)
+// RUN: %host-build-swift -swift-version 5 -emit-library -o %t/%target-library-name(MacroDefinition) -module-name=MacroDefinition %S/Inputs/syntax_macro_definitions.swift -g -no-toolchain-stdlib-rpath
+
+// RUN: %target-typecheck-verify-swift -enable-experimental-feature ExtensionMacros -swift-version 5 -load-plugin-library %t/%target-library-name(MacroDefinition) -module-name MacroUser -DTEST_DIAGNOSTICS -swift-version 5 -I %t
+protocol DefaultInit {
+  init()
+}
+
+@attached(extension, conformances: DefaultInit)
+@attached(member, conformances: DefaultInit, names: named(init()))
+macro DefaultInit() = #externalMacro(module: "MacroDefinition", type: "RequiredDefaultInitMacro")
+
+@DefaultInit
+class C { }
+
+@DefaultInit
+class D: C { }
+
+@DefaultInit
+struct E { }