Merge pull request swiftlang#35717 from xymus/fix-extensions-with-if-config

[ModuleInterface] Don't print extensions only for a nested #if

Author: xymus

lib/AST/ASTPrinter.cpp

@@ -1802,6 +1802,11 @@ bool ShouldPrintChecker::shouldPrint(const Decl *D,
     }
     return false;
   }
+
+  if (isa<IfConfigDecl>(D)) {
+    return Options.PrintIfConfig;
+  }
+
   return true;
 }
 

test/ModuleInterface/empty-extension.swift

@@ -9,6 +9,8 @@
 // RUN: %target-swift-frontend-typecheck -emit-module-interface-path %t/out.swiftinterface %s -I %t -swift-version 5 -enable-library-evolution
 // RUN: %FileCheck %s < %t/out.swiftinterface
 
+// REQUIRES: OS=macosx
+
 #if IOI_LIB
 
 public struct IOIImportedType {
@@ -38,12 +40,26 @@ public protocol PublicProto {
   func foo()
 }
 extension IOIImportedType : PublicProto {}
+
+extension IOIImportedType {
+  #if os(iOS)
+    public func funcForAnotherOS() {}
+  #endif
+}
 // CHECK-NOT: IOIImportedType
+// CHECK-NOT: funcForAnotherOS
 
 extension NormalImportedType : PublicProto {}
 // CHECK: extension NormalImportedType
 
 extension ExportedType : PublicProto {}
 // CHECK: extension ExportedType
 
+extension NormalImportedType {
+  #if os(macOS)
+    public func funcForThisOS() {};
+  #endif
+}
+// CHECK: funcForThisOS
+
 #endif