[swift-ide-test] Make -skip-overrides more aggressive in its pruning.

Cope with imported protocol members as well, which pares down the size
of Swift API projections considerably. Fixes rdar://problem/25223995.

Author: DougGregor

lib/AST/ASTPrinter.cpp

@@ -40,6 +40,7 @@
 #include "swift/Strings.h"
 #include "clang/AST/ASTContext.h"
 #include "clang/AST/Decl.h"
+#include "clang/AST/DeclObjC.h"
 #include "clang/Basic/Module.h"
 #include "llvm/ADT/StringSwitch.h"
 #include "llvm/Support/ConvertUTF.h"
@@ -1549,6 +1550,28 @@ bool swift::shouldPrint(const Decl *D, PrintOptions &Options) {
     if (auto *VD = dyn_cast<ValueDecl>(D)) {
       if (VD->getOverriddenDecl()) return false;
       if (!VD->getSatisfiedProtocolRequirements().empty()) return false;
+
+      if (auto clangDecl = VD->getClangDecl()) {
+        // If the Clang declaration is from a protocol but was mirrored into
+        // class or extension thereof, treat it as an override.
+        if (isa<clang::ObjCProtocolDecl>(clangDecl->getDeclContext()) &&
+            VD->getDeclContext()->getAsClassOrClassExtensionContext())
+          return false;
+
+        // Check whether Clang considers it an override.
+        if (auto objcMethod = dyn_cast<clang::ObjCMethodDecl>(clangDecl)) {
+          SmallVector<const clang::ObjCMethodDecl *, 4> overriddenMethods;
+          objcMethod->getOverriddenMethods(overriddenMethods);
+          if (!overriddenMethods.empty()) return false;
+        } else if (auto objcProperty
+                     = dyn_cast<clang::ObjCPropertyDecl>(clangDecl)) {
+          if (auto getter = objcProperty->getGetterMethodDecl()) {
+            SmallVector<const clang::ObjCMethodDecl *, 4> overriddenMethods;
+            getter->getOverriddenMethods(overriddenMethods);
+            if (!overriddenMethods.empty()) return false;
+          }
+        }
+      }
     }
   }