[Macros] Allow synthesized member macros to add member type and method decls.

Author: hborla

lib/Sema/TypeCheckDecl.cpp

@@ -2789,6 +2789,13 @@ static ArrayRef<Decl *> evaluateMembersRequest(
     }
   }
 
+  // Expand synthesized member macros.
+  auto *mutableDecl = const_cast<Decl *>(idc->getDecl());
+  (void)evaluateOrDefault(
+      ctx.evaluator,
+      ExpandSynthesizedMemberMacroRequest{mutableDecl},
+      false);
+
   // If the decl has a @main attribute, we need to force synthesis of the
   // $main function.
   (void) evaluateOrDefault(

lib/Sema/TypeCheckStorage.cpp

@@ -114,7 +114,6 @@ static void computeLoweredStoredProperties(NominalTypeDecl *decl,
     (void)decl->getTypeWrapperProperty();
 
   // Expand synthesized member macros.
-  // FIXME: Member macros can add members other than stored properties.
   auto &ctx = decl->getASTContext();
   evaluateOrDefault(ctx.evaluator,
                     ExpandSynthesizedMemberMacroRequest{decl},

test/Macros/Inputs/syntax_macro_definitions.swift

@@ -346,3 +346,32 @@ public struct AccessViaStorageMacro: AccessorDeclarationMacro {
     ]
   }
 }
+
+public struct AddMembers: MemberDeclarationMacro {
+  public static func expansion(
+    of node: AttributeSyntax,
+    attachedTo decl: DeclSyntax,
+    in context: inout MacroExpansionContext
+  ) throws -> [DeclSyntax] {
+    let storageStruct: StructDeclSyntax =
+      """
+      struct Nested {}
+      """
+
+    let storageVariable: VariableDeclSyntax =
+      """
+      var value: Int = 0
+      """
+
+    let instanceMethod: FunctionDeclSyntax =
+      """
+      func method() { print("synthesized method") }
+      """
+
+    return [
+      DeclSyntax(storageStruct),
+      DeclSyntax(storageVariable),
+      DeclSyntax(instanceMethod),
+    ]
+  }
+}

test/Macros/macro_expand_synthesized_members.swift

@@ -0,0 +1,28 @@
+// RUN: %empty-directory(%t)
+// RUN: %target-build-swift -I %swift-host-lib-dir -L %swift-host-lib-dir -emit-library -o %t/%target-library-name(MacroDefinition) -module-name=MacroDefinition %S/Inputs/syntax_macro_definitions.swift -g -no-toolchain-stdlib-rpath
+// RUNx: %target-swift-frontend -dump-ast -enable-experimental-feature Macros -load-plugin-library %t/%target-library-name(MacroDefinition) -I %swift-host-lib-dir %s -module-name MacroUser 2>&1 | %FileCheck --check-prefix CHECK-AST %s
+// RUN: %target-typecheck-verify-swift -enable-experimental-feature Macros -load-plugin-library %t/%target-library-name(MacroDefinition) -I %swift-host-lib-dir -module-name MacroUser -DTEST_DIAGNOSTICS -swift-version 5
+// RUN: %target-build-swift -enable-experimental-feature Macros -load-plugin-library %t/%target-library-name(MacroDefinition) -I %swift-host-lib-dir -L %swift-host-lib-dir %s -o %t/main -module-name MacroUser -swift-version 5
+// RUN: %target-run %t/main | %FileCheck %s
+// REQUIRES: executable_test
+
+// FIXME: Swift parser is not enabled on Linux CI yet.
+// REQUIRES: OS=macosx
+
+@attached(synthesizedMembers) macro addMembers() = #externalMacro(module: "MacroDefinition", type: "AddMembers")
+
+@addMembers
+struct S {
+  func useSynthesized() {
+    print(s.value)
+    print(S.Nested())
+    s.method()
+  }
+}
+
+let s = S()
+
+// CHECK: 0
+// CHECK: Nested
+// CHECK: synthesized method
+s.useSynthesized()