Apply the @_alwaysEmitConformanceMetadata semantics to conformances originating from macro-expanded declarations and extensions

Existing code does not visit such declarations and does not mark them to be preserved in the binary even if not public and used.

Resolves rdar://127903662

Author: artemcm

lib/SILOptimizer/Mandatory/AlwaysEmitConformanceMetadataPreservation.cpp

@@ -73,6 +73,10 @@ class AlwaysEmitMetadataConformanceCollector : public ASTWalker {
         AlwaysEmitMetadataConformanceDecls.push_back(ETD->getExtendedNominal());
     }
 
+    // Visit peers expanded from macros
+    D->visitAuxiliaryDecls([&](Decl *decl) { decl->walk(*this); },
+                           /*visitFreestandingExpanded=*/false);
+
     return Action::Continue();
   }
 };
@@ -90,8 +94,12 @@ class AlwaysEmitConformanceMetadataPreservation : public SILModuleTransform {
         for (const auto File : M.getSwiftModule()->getFiles())
           File->getTopLevelDecls(TopLevelDecls);
       } else {
-        for (const auto Primary : M.getSwiftModule()->getPrimarySourceFiles())
+        for (const auto Primary : M.getSwiftModule()->getPrimarySourceFiles()) {
           Primary->getTopLevelDecls(TopLevelDecls);
+	  // Visit macro expanded extensions
+	  if (auto *synthesizedPrimary = Primary->getSynthesizedFile())
+	    synthesizedPrimary->getTopLevelDecls(TopLevelDecls);
+	}
       }
     }
     for (auto *TLD : TopLevelDecls)

test/Reflection/Inputs/Macros.swift

@@ -0,0 +1,77 @@
+import SwiftDiagnostics
+import SwiftOperators
+import SwiftSyntax
+import SwiftSyntaxBuilder
+import SwiftSyntaxMacros
+
+public struct AddStructDeclMacro: DeclarationMacro {
+    public static func expansion(
+      of node: some FreestandingMacroExpansionSyntax,
+      in context: some MacroExpansionContext
+    ) throws -> [DeclSyntax] {
+        return [
+            """
+            struct MacroAddedStruct : TestEntity {}
+            """
+        ]
+    }
+}
+
+public struct AddPeerStructMacro: PeerMacro {
+    public static func expansion(
+      of node: AttributeSyntax,
+      providingPeersOf declaration: some DeclSyntaxProtocol,
+      in context: some MacroExpansionContext
+    ) throws -> [DeclSyntax] {
+        let name = declaration.declName
+        return [
+            """
+            struct _Peer_\(name) : TestEntity {}
+            """
+        ]
+    }
+}
+
+public struct AddExtensionMacro: ExtensionMacro {
+  public static func expansion(
+    of node: AttributeSyntax,
+    attachedTo declaration: some DeclGroupSyntax,
+    providingExtensionsOf type: some TypeSyntaxProtocol,
+    conformingTo protocols: [TypeSyntax],
+    in context: some MacroExpansionContext
+  ) throws -> [ExtensionDeclSyntax] {
+    let typeName = declaration.declGroupName
+    return protocols.map {
+      ("""
+      extension \(typeName): \($0) {
+        struct _Extension_\($0): \($0) {}
+      }
+      """ as DeclSyntax)
+      .cast(ExtensionDeclSyntax.self)
+    }
+  }
+}
+
+extension DeclSyntaxProtocol {
+    var declName: TokenSyntax {
+        if let varDecl = self.as(VariableDeclSyntax.self),
+           let first = varDecl.bindings.first,
+           let pattern = first.pattern.as(IdentifierPatternSyntax.self) {
+            return pattern.identifier.trimmed
+        } else if let funcDecl = self.as(FunctionDeclSyntax.self) {
+            return funcDecl.name.trimmed
+        } else if let structDecl = self.as(StructDeclSyntax.self) {
+            return structDecl.name.trimmed
+        }
+        fatalError("Not implemented")
+    }
+}
+
+extension DeclGroupSyntax {
+    var declGroupName: TokenSyntax {
+        if let structDecl = self.as(StructDeclSyntax.self) {
+            return structDecl.name.trimmed
+        }
+        fatalError("Not implemented")
+    }
+}

test/Reflection/preserve_conformance_metadata_attr_macros.swift

@@ -0,0 +1,41 @@
+// REQUIRES: objc_interop
+// RUN: %empty-directory(%t)
+// RUN: %empty-directory(%t/includes)
+
+// Build support Protocols module
+// RUN: %target-build-swift %S/Inputs/PreservedConformanceProtocols.swift -parse-as-library -emit-module -emit-library -module-name PreservedConformanceProtocols -o %t/includes/PreservedConformanceProtocols.o
+
+// Build the macro library
+// RUN: %host-build-swift -swift-version 5 -emit-library -o %t/%target-library-name(MacroDefinition) -module-name=MacroDefinition %S/Inputs/Macros.swift -g -no-toolchain-stdlib-rpath
+
+// Build the test into a binary
+// RUN: %target-build-swift %s -parse-as-library -emit-module -emit-library -module-name PreservedConformances -O -whole-module-optimization -I %t/includes -o %t/PreservedConformances -Xlinker %t/includes/PreservedConformanceProtocols.o -load-plugin-library %t/%target-library-name(MacroDefinition)
+
+// RUN: %target-swift-reflection-dump %t/PreservedConformances | %FileCheck %s
+
+import PreservedConformanceProtocols
+
+@freestanding(declaration, names: named(MacroAddedStruct))
+macro AddMacroAddedStruct() = #externalMacro(module: "MacroDefinition", type: "AddStructDeclMacro")
+
+@attached(peer, names: prefixed(_Peer_))
+macro AddPeerStruct() = #externalMacro(module: "MacroDefinition", type: "AddPeerStructMacro")
+
+@attached(extension, conformances: TestEntity, names: prefixed(_extension_), named(_Extension_TestEntity))
+macro AddExtension() = #externalMacro(module: "MacroDefinition", type: "AddExtensionMacro")
+
+#AddMacroAddedStruct
+
+struct internalTestEntity : TestEntity {}
+public struct publicTestEntity : TestEntity {}
+@AddPeerStruct
+struct internalMacroAidedEntityHelper {}
+@AddExtension
+struct internalMacroExtensionAidedEntityHelper {}
+// CHECK: CONFORMANCES:
+// CHECK: =============
+// CHECK-DAG: 21PreservedConformances16publicTestEntityV (PreservedConformances.publicTestEntity) : PreservedConformanceProtocols.TestEntity
+// CHECK-DAG: 21PreservedConformances18internalTestEntityV (PreservedConformances.internalTestEntity) : PreservedConformanceProtocols.TestEntity
+// CHECK-DAG: 21PreservedConformances16MacroAddedStructV (PreservedConformances.MacroAddedStruct) : PreservedConformanceProtocols.TestEntity
+// CHECK-DAG: 21PreservedConformances36_Peer_internalMacroAidedEntityHelperV (PreservedConformances._Peer_internalMacroAidedEntityHelper) : PreservedConformanceProtocols.TestEntity
+// CHECK-DAG: 21PreservedConformances39internalMacroExtensionAidedEntityHelperV (PreservedConformances.internalMacroExtensionAidedEntityHelper) : PreservedConformanceProtocols.TestEntity