[Module printing] Don't print attached macros in generated interfaces

Macros are expanded as part of interface generation, so they shouldn't
also be printed into the Swift interface.

Fixes rdar://109378191.

Author: DougGregor

include/swift/AST/PrintOptions.h

@@ -350,6 +350,9 @@ struct PrintOptions {
   /// prevent printing from doing "extra" work.
   bool PrintCurrentMembersOnly = false;
 
+  /// Whether to suppress printing of custom attributes that are expanded macros.
+  bool SuppressExpandedMacros = true;
+
   /// List of attribute kinds that should not be printed.
   std::vector<AnyAttrKind> ExcludeAttrList = {DAK_Transparent, DAK_Effects,
                                               DAK_FixedLayout,
@@ -658,6 +661,7 @@ struct PrintOptions {
     result.EnumRawValues = EnumRawValueMode::PrintObjCOnly;
     result.MapCrossImportOverlaysToDeclaringModule = true;
     result.PrintCurrentMembersOnly = false;
+    result.SuppressExpandedMacros = true;
     return result;
   }
 

lib/AST/Attr.cpp

@@ -790,6 +790,15 @@ void DeclAttributes::print(ASTPrinter &Printer, const PrintOptions &Options,
     if (Options.excludeAttrKind(DA->getKind()))
       continue;
 
+    // If we're supposed to suppress expanded macros, check whether this is
+    // a macro.
+    if (Options.SuppressExpandedMacros) {
+      if (auto customAttr = dyn_cast<CustomAttr>(DA)) {
+        if (D->getResolvedMacro(const_cast<CustomAttr *>(customAttr)))
+          continue;
+      }
+    }
+
     // If this attribute is only allowed because this is a Clang decl, don't
     // print it.
     if (D && D->hasClangNode()

test/Macros/macro_expand_conformances.swift

@@ -26,6 +26,7 @@ public struct PublicEquatable {
   public init() { }
 }
 
+// INTERFACE-NOT: @Equatable
 // INTERFACE: public struct PublicEquatable
 // INTERFACE: extension ModuleWithEquatable.PublicEquatable : Swift.Equatable