clang-format: Prevent ObjC code from confusing the braced-init detection

This was leading to bad formatting, e.g.:
Before:
  f(^{
      @autoreleasepool {
        if (a) {
          g();
  }
  }
  });

After:
  f(^{
      @autoreleasepool {
        if (a) {
          g();
        }
      }
  });

llvm-svn: 203777

clang/lib/Format/UnwrappedLineParser.cpp

@@ -357,6 +357,7 @@ void UnwrappedLineParser::calculateBraceTypes() {
         LBraceStack.pop_back();
       }
       break;
+    case tok::at:
     case tok::semi:
     case tok::kw_if:
     case tok::kw_while:

clang/unittests/Format/FormatTest.cpp

@@ -8062,6 +8062,14 @@ TEST_F(FormatTest, FormatsBlocks) {
                "        // ...\n"
                "        int i;\n"
                "    }];");
+
+  verifyFormat("f(^{\n"
+               "    @autoreleasepool {\n"
+               "      if (a) {\n"
+               "        g();\n"
+               "      }\n"
+               "    }\n"
+               "});");
 }
 
 TEST_F(FormatTest, SupportsCRLF) {