Squashed 'third_party/abseil_cpp/' changes from 768eb2ca2..ccdbb5941

ccdbb5941 Export of internal Abseil changes
01f5f81f9 Export of internal Abseil changes
2c92bdc7c Export of internal Abseil changes
e7ebf9803 Export of internal Abseil changes
2eba343b5 Export of internal Abseil changes
a8b03d90e Export of internal Abseil changes
1d31b5c36 Export of internal Abseil changes
da3a87690 Export of internal Abseil changes
8faf20461 Exclude empty directories (#697)
2069dc796 Export of internal Abseil changes
4832bf6bf Added a BUILD file in root to expose license. (#695)
af8f994af Export of internal Abseil changes
33caf1097 Export of internal Abseil changes
cf1a02e2d Export of internal Abseil changes

git-subtree-dir: third_party/abseil_cpp
git-subtree-split: ccdbb5941f992fabda7eae3ce72f55efc17c826a

1 files changed, 49 insertions, 4 deletions

diff --git a/absl/random/internal/distribution_caller.h b/absl/random/internal/distribution_caller.h
index 4e0724440cbc..fc81b787ebe2 100644
--- a/absl/random/internal/distribution_caller.h
+++ b/absl/random/internal/distribution_caller.h
@@ -20,6 +20,8 @@
 #include <utility>
 
 #include "absl/base/config.h"
+#include "absl/base/internal/fast_type_id.h"
+#include "absl/utility/utility.h"
 
 namespace absl {
 ABSL_NAMESPACE_BEGIN
@@ -30,14 +32,57 @@ namespace random_internal {
 // to intercept such calls.
 template <typename URBG>
 struct DistributionCaller {
-  // Call the provided distribution type. The parameters are expected
-  // to be explicitly specified.
-  // DistrT is the distribution type.
+  // SFINAE to detect whether the URBG type includes a member matching
+  // bool InvokeMock(base_internal::FastTypeIdType, void*, void*).
+  //
+  // These live inside BitGenRef so that they have friend access
+  // to MockingBitGen. (see similar methods in DistributionCaller).
+  template <template <class...> class Trait, class AlwaysVoid, class... Args>
+  struct detector : std::false_type {};
+  template <template <class...> class Trait, class... Args>
+  struct detector<Trait, absl::void_t<Trait<Args...>>, Args...>
+      : std::true_type {};
+
+  template <class T>
+  using invoke_mock_t = decltype(std::declval<T*>()->InvokeMock(
+      std::declval<::absl::base_internal::FastTypeIdType>(),
+      std::declval<void*>(), std::declval<void*>()));
+
+  using HasInvokeMock = typename detector<invoke_mock_t, void, URBG>::type;
+
+  // Default implementation of distribution caller.
   template <typename DistrT, typename... Args>
-  static typename DistrT::result_type Call(URBG* urbg, Args&&... args) {
+  static typename DistrT::result_type Impl(std::false_type, URBG* urbg,
+                                           Args&&... args) {
     DistrT dist(std::forward<Args>(args)...);
     return dist(*urbg);
   }
+
+  // Mock implementation of distribution caller.
+  // The underlying KeyT must match the KeyT constructed by MockOverloadSet.
+  template <typename DistrT, typename... Args>
+  static typename DistrT::result_type Impl(std::true_type, URBG* urbg,
+                                           Args&&... args) {
+    using ResultT = typename DistrT::result_type;
+    using ArgTupleT = std::tuple<absl::decay_t<Args>...>;
+    using KeyT = ResultT(DistrT, ArgTupleT);
+
+    ArgTupleT arg_tuple(std::forward<Args>(args)...);
+    ResultT result;
+    if (!urbg->InvokeMock(::absl::base_internal::FastTypeId<KeyT>(), &arg_tuple,
+                          &result)) {
+      auto dist = absl::make_from_tuple<DistrT>(arg_tuple);
+      result = dist(*urbg);
+    }
+    return result;
+  }
+
+  // Default implementation of distribution caller.
+  template <typename DistrT, typename... Args>
+  static typename DistrT::result_type Call(URBG* urbg, Args&&... args) {
+    return Impl<DistrT, Args...>(HasInvokeMock{}, urbg,
+                                 std::forward<Args>(args)...);
+  }
 };
 
 }  // namespace random_internal