[FlowSensitive] [Optional] Fix absl::in_place (llvm#163897)

The mock was not accurate, absl defines in_place[_t] as an alias to
std::in_place[_t].

Author: fmayer

clang/lib/Analysis/FlowSensitive/Models/UncheckedOptionalAccessModel.cpp

@@ -241,9 +241,9 @@ auto nulloptTypeDecl() {
 auto hasNulloptType() { return hasType(nulloptTypeDecl()); }
 
 auto inPlaceClass() {
-  return recordDecl(hasAnyName("std::in_place_t", "absl::in_place_t",
-                               "base::in_place_t", "folly::in_place_t",
-                               "bsl::in_place_t"));
+  return namedDecl(hasAnyName("std::in_place_t", "absl::in_place_t",
+                              "base::in_place_t", "folly::in_place_t",
+                              "bsl::in_place_t"));
 }
 
 auto isOptionalNulloptConstructor() {

clang/unittests/Analysis/FlowSensitive/MockHeaders.cpp

@@ -459,6 +459,10 @@ struct is_scalar
 template <>
 struct is_scalar<nullptr_t> : public true_type {};
 
+struct in_place_t {};
+
+constexpr in_place_t in_place;
+
 } // namespace std
 
 #endif // STD_TYPE_TRAITS_H
@@ -511,9 +515,8 @@ using remove_reference_t = typename std::remove_reference<T>::type;
 template <typename T>
 using decay_t = typename std::decay<T>::type;
 
-struct in_place_t {};
-
-constexpr in_place_t in_place;
+using std::in_place;
+using std::in_place_t;
 } // namespace absl
 
 #endif // ABSL_TYPE_TRAITS_H
@@ -589,9 +592,6 @@ static constexpr char StdOptionalHeader[] = R"(
 
 namespace std {
 
-struct in_place_t {};
-constexpr in_place_t in_place;
-
 struct nullopt_t {
   constexpr explicit nullopt_t() {}
 };