Bug 1142503 - don't use QueryInterface when the compiler can do the cast for us; r=ehsan

Calling QueryInterface with a statically known IID should typically not
be necessary.  In those cases where it's not, the compiler can do the
cast for us, though we have to supply the reference-counting that
QueryInterface would do.

In passing, several redundant null-checks for the result of |new T| have
been deleted.

editor/composer/nsComposerCommandsUpdater.cpp

@@ -385,9 +385,7 @@ nsComposerCommandsUpdater::Notify(nsITimer *timer)
 nsresult
 NS_NewComposerCommandsUpdater(nsISelectionListener** aInstancePtrResult)
 {
-  nsComposerCommandsUpdater* newThang = new nsComposerCommandsUpdater;
-  NS_ENSURE_TRUE(newThang, NS_ERROR_OUT_OF_MEMORY);
-
-  return newThang->QueryInterface(NS_GET_IID(nsISelectionListener),
-                                  (void **)aInstancePtrResult);
+  nsRefPtr<nsComposerCommandsUpdater> newThang = new nsComposerCommandsUpdater;
+  newThang.forget(aInstancePtrResult);
+  return NS_OK;
 }

editor/libeditor/nsHTMLURIRefObject.cpp

@@ -254,7 +254,7 @@ nsresult NS_NewHTMLURIRefObject(nsIURIRefObject** aResult, nsIDOMNode* aNode)
     *aResult = 0;
     return rv;
   }
-  return refObject->QueryInterface(NS_GET_IID(nsIURIRefObject),
-                                   (void**)aResult);
+  refObject.forget(aResult);
+  return NS_OK;
 }
 

editor/txtsvc/nsTextServicesDocument.cpp

@@ -2000,7 +2000,7 @@ nsTextServicesDocument::GetDocumentContentRootNode(nsIDOMNode **aNode)
 
     NS_ENSURE_TRUE(bodyElement, NS_ERROR_FAILURE);
 
-    result = bodyElement->QueryInterface(NS_GET_IID(nsIDOMNode), (void **)aNode);
+    bodyElement.forget(aNode);
   }
   else
   {
@@ -2014,7 +2014,7 @@ nsTextServicesDocument::GetDocumentContentRootNode(nsIDOMNode **aNode)
 
     NS_ENSURE_TRUE(docElement, NS_ERROR_FAILURE);
 
-    result = docElement->QueryInterface(NS_GET_IID(nsIDOMNode), (void **)aNode);
+    docElement.forget(aNode);
   }
 
   return result;

embedding/components/commandhandler/nsCommandGroup.cpp

@@ -288,10 +288,10 @@ nsControllerCommandGroup::IsCommandInGroup(const char *aCommand, const char *aGr
 NS_IMETHODIMP
 nsControllerCommandGroup::GetGroupsEnumerator(nsISimpleEnumerator **_retval)
 {
-  nsGroupsEnumerator *groupsEnum = new nsGroupsEnumerator(mGroupsHash);
-  if (!groupsEnum) return NS_ERROR_OUT_OF_MEMORY;
+  nsRefPtr<nsGroupsEnumerator> groupsEnum = new nsGroupsEnumerator(mGroupsHash);
 
-  return groupsEnum->QueryInterface(NS_GET_IID(nsISimpleEnumerator), (void **)_retval);
+  groupsEnum.forget(_retval);
+  return NS_OK;
 }
 
 /* nsISimpleEnumerator getEnumeratorForGroup (in DOMString aGroup); */
@@ -301,10 +301,10 @@ nsControllerCommandGroup::GetEnumeratorForGroup(const char *aGroup, nsISimpleEnu
   nsDependentCString groupKey(aGroup);
   nsTArray<nsCString> *commandList = mGroupsHash.Get(groupKey); // may be null
 
-  nsNamedGroupEnumerator *theGroupEnum = new nsNamedGroupEnumerator(commandList);
-  if (!theGroupEnum) return NS_ERROR_OUT_OF_MEMORY;
+  nsRefPtr<nsNamedGroupEnumerator> theGroupEnum = new nsNamedGroupEnumerator(commandList);
 
-  return theGroupEnum->QueryInterface(NS_GET_IID(nsISimpleEnumerator), (void **)_retval);
+  theGroupEnum.forget(_retval);
+  return NS_OK;
 }
 
 #if 0

embedding/components/find/nsWebBrowserFind.cpp

@@ -409,8 +409,8 @@ nsresult nsWebBrowserFind::GetRootNode(nsIDOMDocument* aDomDoc,
     rv = htmlDoc->GetBody(getter_AddRefs(bodyElement));
     NS_ENSURE_SUCCESS(rv, rv);
     NS_ENSURE_ARG_POINTER(bodyElement);
-    return bodyElement->QueryInterface(NS_GET_IID(nsIDOMNode),
-                                       (void **)aNode);
+    bodyElement.forget(aNode);
+    return NS_OK;
   }
 
   // For non-HTML documents, the content root node will be the doc element.
@@ -418,7 +418,8 @@ nsresult nsWebBrowserFind::GetRootNode(nsIDOMDocument* aDomDoc,
   rv = aDomDoc->GetDocumentElement(getter_AddRefs(docElement));
   NS_ENSURE_SUCCESS(rv, rv);
   NS_ENSURE_ARG_POINTER(docElement);
-  return docElement->QueryInterface(NS_GET_IID(nsIDOMNode), (void **)aNode);
+  docElement.forget(aNode);
+  return NS_OK;
 }
 
 nsresult nsWebBrowserFind::SetRangeAroundDocument(nsIDOMRange* aSearchRange,

intl/strres/nsStringBundle.cpp

@@ -651,9 +651,8 @@ nsStringBundleService::CreateExtensibleBundle(const char* aCategory,
     return res;
   }
 
-  res = bundle->QueryInterface(NS_GET_IID(nsIStringBundle), (void**) aResult);
-
-  return res;
+  bundle.forget(aResult);
+  return NS_OK;
 }
 
 #define GLOBAL_PROPERTIES "chrome://global/locale/global-strres.properties"

security/manager/ssl/src/PSMContentListener.cpp

@@ -270,17 +270,13 @@ PSMContentListener::DoContent(const nsACString & aContentType,
                                nsIStreamListener ** aContentHandler,
                                bool * aAbortProcess)
 {
-  PSMContentDownloader *downLoader;
   uint32_t type;
   type = getPSMContentType(PromiseFlatCString(aContentType).get());
   PR_LOG(gPIPNSSLog, PR_LOG_DEBUG, ("PSMContentListener::DoContent\n"));
   if (type != PSMContentDownloader::UNKNOWN_TYPE) {
-    downLoader = new PSMContentDownloader(type);
-    if (downLoader) {
-      downLoader->QueryInterface(NS_GET_IID(nsIStreamListener), 
-                                            (void **)aContentHandler);
-      return NS_OK;
-    }
+    nsRefPtr<PSMContentDownloader> downLoader = new PSMContentDownloader(type);
+    downLoader.forget(aContentHandler);
+    return NS_OK;
   }
   return NS_ERROR_FAILURE;
 }

toolkit/components/places/nsNavHistoryResult.cpp

@@ -4323,8 +4323,9 @@ nsNavHistoryResult::GetRoot(nsINavHistoryContainerResultNode** aRoot)
     *aRoot = nullptr;
     return NS_ERROR_FAILURE;
   }
-  return mRootNode->QueryInterface(NS_GET_IID(nsINavHistoryContainerResultNode),
-                                   reinterpret_cast<void**>(aRoot));
+  nsRefPtr<nsNavHistoryContainerResultNode> node(mRootNode);
+  node.forget(aRoot);
+  return NS_OK;
 }
 
 

widget/nsPrintSettingsImpl.cpp

@@ -1110,8 +1110,9 @@ nsPrintSettings::GetPageRanges(nsTArray<int32_t> &aPages)
 nsresult 
 nsPrintSettings::_Clone(nsIPrintSettings **_retval)
 {
-  nsPrintSettings* printSettings = new nsPrintSettings(*this);
-  return printSettings->QueryInterface(NS_GET_IID(nsIPrintSettings), (void**)_retval); // ref counts
+  nsRefPtr<nsPrintSettings> printSettings = new nsPrintSettings(*this);
+  printSettings.forget(_retval);
+  return NS_OK;
 }
 
 /* nsIPrintSettings clone (); */

widget/windows/nsImageClipboard.cpp

@@ -1,4 +1,4 @@
-/* -*- Mode: C++; tab-width: 4; indent-tabs-mode: nil; c-basic-offset: 4 -*- */
+/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
 /* This Source Code Form is subject to the terms of the Mozilla Public
  * License, v. 2.0. If a copy of the MPL was not distributed with this
  * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
@@ -251,8 +251,9 @@ nsImageFromClipboard ::GetEncodedImageStream (unsigned char * aClipboardData, co
       if (NS_SUCCEEDED(rv)){
         rv = encoder->InitFromData(rgbData, 0, width, height, 3 * width /* RGB * # pixels in a row */, 
                                    imgIEncoder::INPUT_FORMAT_RGB, EmptyString());
-        if (NS_SUCCEEDED(rv))
-          encoder->QueryInterface(NS_GET_IID(nsIInputStream), (void **) aInputStream);
+        if (NS_SUCCEEDED(rv)) {
+          encoder.forget(aInputStream);
+        }
       }
     }
     delete [] rgbData;

widget/windows/nsPrintSettingsWin.cpp

@@ -118,8 +118,9 @@ NS_IMETHODIMP nsPrintSettingsWin::SetDevMode(DEVMODEW * aDevMode)
 nsresult 
 nsPrintSettingsWin::_Clone(nsIPrintSettings **_retval)
 {
-  nsPrintSettingsWin* printSettings = new nsPrintSettingsWin(*this);
-  return printSettings->QueryInterface(NS_GET_IID(nsIPrintSettings), (void**)_retval); // ref counts
+  nsRefPtr<nsPrintSettingsWin> printSettings = new nsPrintSettingsWin(*this);
+  printSettings.forget(_retval);
+  return NS_OK;
 }
 
 //-------------------------------------------

xpcom/io/nsAppFileLocationProvider.cpp

@@ -228,7 +228,8 @@ nsAppFileLocationProvider::GetFile(const char* aProp, bool* aPersistent,
   }
 
   if (localFile && NS_SUCCEEDED(rv)) {
-    return localFile->QueryInterface(NS_GET_IID(nsIFile), (void**)aResult);
+    localFile.forget(aResult);
+    return NS_OK;
   }
 
   return rv;

xpfe/appshell/nsWindowMediator.cpp

@@ -195,11 +195,9 @@ nsWindowMediator::GetEnumerator(const char16_t* inType, nsISimpleEnumerator** ou
   NS_ENSURE_ARG_POINTER(outEnumerator);
   NS_ENSURE_STATE(mReady);
 
-  nsAppShellWindowEnumerator *enumerator = new nsASDOMWindowEarlyToLateEnumerator(inType, *this);
-  if (enumerator)
-    return enumerator->QueryInterface(NS_GET_IID(nsISimpleEnumerator) , (void**)outEnumerator);
-
-  return NS_ERROR_OUT_OF_MEMORY;
+  nsRefPtr<nsAppShellWindowEnumerator> enumerator = new nsASDOMWindowEarlyToLateEnumerator(inType, *this);
+  enumerator.forget(outEnumerator);
+  return NS_OK;
 }
 
 NS_IMETHODIMP
@@ -209,11 +207,9 @@ nsWindowMediator::GetXULWindowEnumerator(const char16_t* inType, nsISimpleEnumer
   NS_ENSURE_ARG_POINTER(outEnumerator);
   NS_ENSURE_STATE(mReady);
 
-  nsAppShellWindowEnumerator *enumerator = new nsASXULWindowEarlyToLateEnumerator(inType, *this);
-  if (enumerator)
-    return enumerator->QueryInterface(NS_GET_IID(nsISimpleEnumerator) , (void**)outEnumerator);
-
-  return NS_ERROR_OUT_OF_MEMORY;
+  nsRefPtr<nsAppShellWindowEnumerator> enumerator = new nsASXULWindowEarlyToLateEnumerator(inType, *this);
+  enumerator.forget(outEnumerator);
+  return NS_OK;
 }
 
 NS_IMETHODIMP