clang-format: Improve understanding of decltype.

Before:
  SomeFunction([](decltype(x), A * a) {});

After:
  SomeFunction([](decltype(x), A *a) {});

llvm-svn: 207961
diff --git a/clang/unittests/Format/FormatTest.cpp b/clang/unittests/Format/FormatTest.cpp
index 1380dd8..7db87cb 100644
--- a/clang/unittests/Format/FormatTest.cpp
+++ b/clang/unittests/Format/FormatTest.cpp
@@ -8432,6 +8432,9 @@
   verifyFormat("SomeFunction([]() { // A cool function...\n"
                "  return 43;\n"
                "});");
+  verifyFormat("void f() {\n"
+               "  SomeFunction([](decltype(x), A *a) {});\n"
+               "}");
 
   // Lambdas with return types.
   verifyFormat("int c = []() -> int { return 2; }();\n");