[Macros] Allow @attached(extension) attributes to be suppressed in

module interfaces.

Author: hborla

include/swift/AST/PrintOptions.h

@@ -578,6 +578,11 @@ struct PrintOptions {
   /// If false, we print them as ordinary associated types.
   bool PrintPrimaryAssociatedTypes = true;
 
+  /// Whether or not to print \c @attached(extension) attributes on
+  /// macro declarations. This is used for feature suppression in
+  /// Swift interface printing.
+  bool PrintExtensionMacroAttributes = true;
+
   /// If this is not \c nullptr then function bodies (including accessors
   /// and constructors) will be printed by this function.
   std::function<void(const ValueDecl *, ASTPrinter &)> FunctionBody;

include/swift/Basic/Features.def

@@ -119,10 +119,12 @@ EXPERIMENTAL_FEATURE(StaticAssert, false)
 EXPERIMENTAL_FEATURE(NamedOpaqueTypes, false)
 EXPERIMENTAL_FEATURE(FlowSensitiveConcurrencyCaptures, false)
 EXPERIMENTAL_FEATURE(CodeItemMacros, true)
-EXPERIMENTAL_FEATURE(ExtensionMacros, false)
 EXPERIMENTAL_FEATURE(TupleConformances, false)
 EXPERIMENTAL_FEATURE(InitAccessors, false)
 
+EXPERIMENTAL_FEATURE(ExtensionMacros, false)
+SUPPRESSIBLE_LANGUAGE_FEATURE(ExtensionMacroAttr, 0, "@attached(extension)", true)
+
 // Whether to enable @_used and @_section attributes
 EXPERIMENTAL_FEATURE(SymbolLinkageMarkers, true)
 

lib/AST/ASTPrinter.cpp

@@ -2860,6 +2860,18 @@ static bool usesFeatureExtensionMacros(Decl *decl) {
   return macro->getMacroRoles().contains(MacroRole::Extension);
 }
 
+static bool usesFeatureExtensionMacroAttr(Decl *decl) {
+  return usesFeatureExtensionMacros(decl);
+}
+
+static void suppressingFeatureExtensionMacroAttr(PrintOptions &options,
+                                                 llvm::function_ref<void()> action) {
+  bool originalPrintExtensionMacroAttrs = options.PrintExtensionMacroAttributes;
+  options.PrintExtensionMacroAttributes = false;
+  action();
+  options.PrintExtensionMacroAttributes = originalPrintExtensionMacroAttrs;
+}
+
 static bool usesFeatureAttachedMacros(Decl *decl) {
   auto macro = dyn_cast<MacroDecl>(decl);
   if (!macro)

lib/AST/Attr.cpp

@@ -1371,6 +1371,13 @@ bool DeclAttribute::printImpl(ASTPrinter &Printer, const PrintOptions &Options,
 
   case DAK_MacroRole: {
     auto Attr = cast<MacroRoleAttr>(this);
+
+    // Suppress @attached(extension) if needed.
+    if (!Options.PrintExtensionMacroAttributes &&
+        Attr->getMacroRole() == MacroRole::Extension) {
+      break;
+    }
+
     switch (Attr->getMacroSyntax()) {
     case MacroSyntax::Freestanding:
       Printer.printAttrName("@freestanding");

test/ModuleInterface/macros.swift

@@ -5,7 +5,7 @@
 
 // RUN: %empty-directory(%t)
 
-// RUN: %target-swift-emit-module-interface(%t/Macros.swiftinterface) -module-name Macros %s
+// RUN: %target-swift-emit-module-interface(%t/Macros.swiftinterface) -enable-experimental-feature ExtensionMacros -module-name Macros %s
 // RUN: %FileCheck %s < %t/Macros.swiftinterface --check-prefix CHECK
 // RUN: %target-swift-frontend -compile-module-from-interface %t/Macros.swiftinterface -o %t/Macros.swiftmodule
 
@@ -49,5 +49,12 @@
 // CHECK-NEXT: #endif
 @attached(accessor, names: named(init)) public macro AccessorInitFunc() = #externalMacro(module: "SomeModule", type: "AccessorInitFuncMacro")
 
+// CHECK: #if compiler(>=5.3) && $Macros && $AttachedMacros
+// CHECK: @attached(extension) @attached(conformance) public macro AddSendable() = #externalMacro(module: "SomeModule", type: "SendableExtensionMacro")
+// CHECK-NEXT: #else
+// CHECK: @attached(conformance) public macro AddSendable() = #externalMacro(module: "SomeModule", type: "SendableExtensionMacro")
+// CHECK-NEXT: #endif
+@attached(extension) @attached(conformance) public macro AddSendable() = #externalMacro(module: "SomeModule", type: "SendableExtensionMacro")
+
 // CHECK-NOT: internalStringify
 @freestanding(expression) macro internalStringify<T>(_ value: T) -> (T, String) = #externalMacro(module: "SomeModule", type: "StringifyMacro")