[Clang][AST] Print attributes of Obj-C interfaces

When pretty printing an Objective-C interface declaration, Clang
previously didn't print any attributes that are applied to the
declaration.

Author: egorzhdan

clang/lib/AST/DeclPrinter.cpp

@@ -1517,6 +1517,11 @@ void DeclPrinter::VisitObjCInterfaceDecl(ObjCInterfaceDecl *OID) {
     return;
   }
   bool eolnOut = false;
+  if (OID->hasAttrs()) {
+    prettyPrintAttributes(OID);
+    Out << "\n";
+  }
+
   Out << "@interface " << I;
 
   if (auto TypeParams = OID->getTypeParamListAsWritten()) {

clang/test/AST/ast-print-objectivec.m

@@ -21,6 +21,10 @@ - (void)MethI __attribute__((availability(macosx,introduced=10.1.0,deprecated=10
 - (void)methodWithArg:(int)x andAnotherOne:(int)y { }
 @end
 
+__attribute__((availability(macosx,introduced=10.1.0,deprecated=10.2)))
+@interface InterfaceWithAttribute
+@end
+
 // CHECK: @protocol P
 // CHECK: - (void)MethP __attribute__((availability(macos, introduced=10.1.0, deprecated=10.2)));
 // CHECK: @end
@@ -45,6 +49,10 @@ - (void)methodWithArg:(int)x andAnotherOne:(int)y { }
 
 // CHECK: @end
 
+// CHECK: __attribute__((availability(macos, introduced=10.1.0, deprecated=10.2)))
+// CHECK: @interface InterfaceWithAttribute
+// CHECK: @end
+
 @class C1;
 struct __attribute__((objc_bridge_related(C1,,))) S1;