Allow binding captureless lambdas into base::Callback by base::Bind

base/bind_unittest.cc

 // Copyright (c) 2012 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "base/bind.h"
 
 #include <memory>
 #include <utility>
 #include <vector>
 
@@ skipping 1020 matching lines @@
   move_assigns = 0;
   Bind(&VoidPolymorphic<CopyMoveCounter>::Run)
       .Run(CopyMoveCounter(DerivedCopyMoveCounter(
           &copies, &assigns, &move_constructs, &move_assigns)));
   EXPECT_EQ(0, copies);
   EXPECT_EQ(0, assigns);
   EXPECT_EQ(2, move_constructs);
   EXPECT_EQ(0, move_assigns);
 }
 
+TEST_F(BindTest, CapturelessLambda) {
+  EXPECT_FALSE(internal::IsConvertibleToRunType<void>::value);
+  EXPECT_FALSE(internal::IsConvertibleToRunType<int>::value);
+  EXPECT_FALSE(internal::IsConvertibleToRunType<void(*)()>::value);
+  EXPECT_FALSE(internal::IsConvertibleToRunType<void(NoRef::*)()>::value);
+
+  auto f = []() {};
+  EXPECT_TRUE(internal::IsConvertibleToRunType<decltype(f)>::value);
+
+  int i = 0;
+  auto g = [i]() {};
+  EXPECT_FALSE(internal::IsConvertibleToRunType<decltype(g)>::value);
+
+  auto h = [](int, double) { return 'k'; };
+  EXPECT_TRUE((std::is_same<
+      char(int, double),
+      internal::ExtractCallableRunType<decltype(h)>>::value));
+
+  EXPECT_EQ(42, Bind([] { return 42; }).Run());
+  EXPECT_EQ(42, Bind([](int i) { return i * 7; }, 6).Run());
+
+  int x = 1;
+  base::Callback<void(int)> cb =
+      Bind([](int* x, int i) { *x *= i; }, Unretained(&x));
+  cb.Run(6);
+  EXPECT_EQ(6, x);
+  cb.Run(7);
+  EXPECT_EQ(42, x);
+}
+
 // Callback construction and assignment tests.
 //   - Construction from an InvokerStorageHolder should not cause ref/deref.
 //   - Assignment from other callback should only cause one ref
 //
 // TODO(ajwong): Is there actually a way to test this?
 
 #if defined(OS_WIN)
 int __fastcall FastCallFunc(int n) {
   return n;
 }
@@ skipping 21 matching lines @@
   base::Callback<void(int)> null_cb;
   ASSERT_TRUE(null_cb.is_null());
   EXPECT_DEATH(base::Bind(null_cb, 42), "");
 }
 
 #endif  // (!defined(NDEBUG) || defined(DCHECK_ALWAYS_ON)) &&
         //     GTEST_HAS_DEATH_TEST
 
 }  // namespace
 }  // namespace base