[Macros] Expand conformance macros as extension macros.

ConformanceMacro now refines ExtensionMacro, so these roles can share
the same expansion request.

Author: hborla

lib/AST/ConformanceLookupTable.cpp

@@ -282,12 +282,8 @@ void ConformanceLookupTable::updateLookupTable(NominalTypeDecl *nominal,
           addInheritedProtocols(nominal,
                                 ConformanceSource::forExplicit(nominal));
 
-          // Expand conformance macros.
-          ASTContext &ctx = nominal->getASTContext();
-          (void)evaluateOrDefault(
-              ctx.evaluator, ExpandConformanceMacros{nominal}, { });
-
           // Expand extension macros.
+          ASTContext &ctx = nominal->getASTContext();
           (void)evaluateOrDefault(
               ctx.evaluator, ExpandExtensionMacros{nominal}, { });
         },

lib/Refactoring/Refactoring.cpp

@@ -8673,15 +8673,8 @@ getMacroExpansionBuffers(MacroDecl *macro, const CustomAttr *attr, Decl *decl) {
     allBufferIDs.append(bufferIDs.begin(), bufferIDs.end());
   }
 
-  if (roles.contains(MacroRole::Conformance)) {
-    if (auto nominal = dyn_cast<NominalTypeDecl>(decl)) {
-      auto bufferIDs = evaluateOrDefault(
-          ctx.evaluator, ExpandConformanceMacros{nominal}, { });
-      allBufferIDs.append(bufferIDs.begin(), bufferIDs.end());
-    }
-  }
-
-  if (roles.contains(MacroRole::Extension)) {
+  if (roles.contains(MacroRole::Conformance) ||
+      roles.contains(MacroRole::Extension)) {
     if (auto nominal = dyn_cast<NominalTypeDecl>(decl)) {
       auto bufferIDs = evaluateOrDefault(
           ctx.evaluator, ExpandExtensionMacros{nominal}, { });

lib/Sema/TypeCheckMacros.cpp

@@ -867,8 +867,10 @@ static uint8_t getRawMacroRole(MacroRole role) {
   case MacroRole::MemberAttribute: return 3;
   case MacroRole::Member: return 4;
   case MacroRole::Peer: return 5;
-  case MacroRole::Conformance: return 6;
   case MacroRole::CodeItem: return 7;
+  // Use the same raw macro role for conformance and extension
+  // in ASTGen.
+  case MacroRole::Conformance:
   case MacroRole::Extension: return 8;
   }
 }
@@ -1156,7 +1158,7 @@ static SourceFile *evaluateAttachedMacro(MacroDecl *macro, Decl *attachedTo,
   std::string extendedType;
   {
     llvm::raw_string_ostream OS(extendedType);
-    if (role == MacroRole::Extension) {
+    if (role == MacroRole::Extension || role == MacroRole::Conformance) {
       auto *nominal = dyn_cast<NominalTypeDecl>(attachedTo);
       PrintOptions options;
       options.FullyQualifiedExtendedTypesIfAmbiguous = true;
@@ -1473,13 +1475,27 @@ ArrayRef<unsigned>
 ExpandExtensionMacros::evaluate(Evaluator &evaluator,
                                 NominalTypeDecl *nominal) const {
   SmallVector<unsigned, 2> bufferIDs;
-  nominal->forEachAttachedMacro(MacroRole::Extension,
-      [&](CustomAttr *attr, MacroDecl *macro) {
-        if (auto bufferID = expandExtensions(attr, macro,
-                                             MacroRole::Extension,
-                                             nominal))
-          bufferIDs.push_back(*bufferID);
-      });
+  for (auto customAttrConst : nominal->getSemanticAttrs().getAttributes<CustomAttr>()) {
+    auto customAttr = const_cast<CustomAttr *>(customAttrConst);
+    auto *macro = nominal->getResolvedMacro(customAttr);
+
+    if (!macro)
+      continue;
+
+    // Prefer the extension role
+    MacroRole role;
+    if (macro->getMacroRoles().contains(MacroRole::Extension)) {
+      role = MacroRole::Extension;
+    } else if (macro->getMacroRoles().contains(MacroRole::Conformance)) {
+      role = MacroRole::Conformance;
+    } else {
+      continue;
+    }
+
+    if (auto bufferID = expandExtensions(customAttr, macro,
+                                         role, nominal))
+      bufferIDs.push_back(*bufferID);
+  }
 
   return nominal->getASTContext().AllocateCopy(bufferIDs);
 }

test/Macros/Inputs/syntax_macro_definitions.swift

@@ -1299,7 +1299,7 @@ public struct DelegatedConformanceMacro: ConformanceMacro, MemberMacro {
   }
 }
 
-extension DelegatedConformanceMacro: ExtensionMacro {
+public struct DelegatedConformanceViaExtensionMacro: ExtensionMacro {
   public static func expansion(
     of node: AttributeSyntax,
     attachedTo decl: some DeclGroupSyntax,

test/Macros/extension_macro_plugin.swift

@@ -24,7 +24,7 @@
 // RUN: %FileCheck %s < %t/macro-expansions.txt
 
 @attached(extension, conformances: P, names: named(requirement))
-macro DelegatedConformance() = #externalMacro(module: "MacroDefinition", type: "DelegatedConformanceMacro")
+macro DelegatedConformance() = #externalMacro(module: "MacroDefinition", type: "DelegatedConformanceViaExtensionMacro")
 
 protocol P {
   static func requirement()

test/Macros/macro_expand_conformances.swift

@@ -53,7 +53,8 @@ enum E {
 }
 
 // CHECK-DUMP: @__swiftmacro_25macro_expand_conformances1S9EquatablefMc_.swift
-// CHECK-DUMP: extension S : Equatable  {}
+// CHECK-DUMP: extension S: Equatable  {
+// CHECK-DUMP: }
 
 // CHECK: true
 requireEquatable(S())
@@ -94,7 +95,8 @@ struct Wrapped: P {
 struct Generic<Element> {}
 
 // CHECK-DUMP: @__swiftmacro_25macro_expand_conformances7Generic20DelegatedConformancefMc_.swift
-// CHECK-DUMP: extension Generic : P where Element: P {}
+// CHECK-DUMP: extension Generic: P where Element: P {
+// CHECK-DUMP: }
 
 func requiresP(_ value: (some P).Type) {
   value.requirement()

test/Macros/macro_expand_extensions.swift

@@ -11,7 +11,7 @@
 // RUN: %target-run %t/main | %FileCheck %s
 
 @attached(extension, conformances: P, names: named(requirement))
-macro DelegatedConformance() = #externalMacro(module: "MacroDefinition", type: "DelegatedConformanceMacro")
+macro DelegatedConformance() = #externalMacro(module: "MacroDefinition", type: "DelegatedConformanceViaExtensionMacro")
 
 protocol P {
   static func requirement()