Export of internal Abseil changes.

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4eacae3ff1b14b1d309e8092185bc10e8a6203cf by Derek Mauro <dmauro@google.com>:

Release SwissTable - a fast, efficient, cache-friendly hash table.

https://www.youtube.com/watch?v=ncHmEUmJZf4

PiperOrigin-RevId: 214816527

--
df8c3dfab3cfb2f4365909a84d0683b193cfbb11 by Derek Mauro <dmauro@google.com>:

Internal change

PiperOrigin-RevId: 214785288

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1eabd5266bbcebc33eecc91e5309b751856a75c8 by Abseil Team <absl-team@google.com>:

Internal change

PiperOrigin-RevId: 214722931

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2ebbfac950f83146b46253038e7dd7dcde9f2951 by Derek Mauro <dmauro@google.com>:

Internal change

PiperOrigin-RevId: 214701684
GitOrigin-RevId: 4eacae3ff1b14b1d309e8092185bc10e8a6203cf
Change-Id: I9ba64e395b22ad7863213d157b8019b082adc19d

1 files changed, 1552 insertions, 0 deletions

diff --git a/absl/container/internal/layout_test.cc b/absl/container/internal/layout_test.cc
new file mode 100644
index 000000000000..f35157a3bd85
--- /dev/null
+++ b/absl/container/internal/layout_test.cc
@@ -0,0 +1,1552 @@
+// Copyright 2018 The Abseil Authors.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//      http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+#include "absl/container/internal/layout.h"
+
+// We need ::max_align_t because some libstdc++ versions don't provide
+// std::max_align_t
+#include <stddef.h>
+#include <cstdint>
+#include <memory>
+#include <sstream>
+#include <type_traits>
+
+#include "gmock/gmock.h"
+#include "gtest/gtest.h"
+#include "absl/base/internal/raw_logging.h"
+#include "absl/types/span.h"
+
+namespace absl {
+namespace container_internal {
+namespace {
+
+using ::absl::Span;
+using ::testing::ElementsAre;
+
+size_t Distance(const void* from, const void* to) {
+  ABSL_RAW_CHECK(from <= to, "Distance must be non-negative");
+  return static_cast<const char*>(to) - static_cast<const char*>(from);
+}
+
+template <class Expected, class Actual>
+Expected Type(Actual val) {
+  static_assert(std::is_same<Expected, Actual>(), "");
+  return val;
+}
+
+using Int128 = int64_t[2];
+
+// Properties of types that this test relies on.
+static_assert(sizeof(int8_t) == 1, "");
+static_assert(alignof(int8_t) == 1, "");
+static_assert(sizeof(int16_t) == 2, "");
+static_assert(alignof(int16_t) == 2, "");
+static_assert(sizeof(int32_t) == 4, "");
+static_assert(alignof(int32_t) == 4, "");
+static_assert(sizeof(Int128) == 16, "");
+static_assert(alignof(Int128) == 8, "");
+
+template <class Expected, class Actual>
+void SameType() {
+  static_assert(std::is_same<Expected, Actual>(), "");
+}
+
+TEST(Layout, ElementType) {
+  {
+    using L = Layout<int32_t>;
+    SameType<int32_t, L::ElementType<0>>();
+    SameType<int32_t, decltype(L::Partial())::ElementType<0>>();
+    SameType<int32_t, decltype(L::Partial(0))::ElementType<0>>();
+  }
+  {
+    using L = Layout<int32_t, int32_t>;
+    SameType<int32_t, L::ElementType<0>>();
+    SameType<int32_t, L::ElementType<1>>();
+    SameType<int32_t, decltype(L::Partial())::ElementType<0>>();
+    SameType<int32_t, decltype(L::Partial())::ElementType<1>>();
+    SameType<int32_t, decltype(L::Partial(0))::ElementType<0>>();
+    SameType<int32_t, decltype(L::Partial(0))::ElementType<1>>();
+  }
+  {
+    using L = Layout<int8_t, int32_t, Int128>;
+    SameType<int8_t, L::ElementType<0>>();
+    SameType<int32_t, L::ElementType<1>>();
+    SameType<Int128, L::ElementType<2>>();
+    SameType<int8_t, decltype(L::Partial())::ElementType<0>>();
+    SameType<int8_t, decltype(L::Partial(0))::ElementType<0>>();
+    SameType<int32_t, decltype(L::Partial(0))::ElementType<1>>();
+    SameType<int8_t, decltype(L::Partial(0, 0))::ElementType<0>>();
+    SameType<int32_t, decltype(L::Partial(0, 0))::ElementType<1>>();
+    SameType<Int128, decltype(L::Partial(0, 0))::ElementType<2>>();
+    SameType<int8_t, decltype(L::Partial(0, 0, 0))::ElementType<0>>();
+    SameType<int32_t, decltype(L::Partial(0, 0, 0))::ElementType<1>>();
+    SameType<Int128, decltype(L::Partial(0, 0, 0))::ElementType<2>>();
+  }
+}
+
+TEST(Layout, ElementTypes) {
+  {
+    using L = Layout<int32_t>;
+    SameType<std::tuple<int32_t>, L::ElementTypes>();
+    SameType<std::tuple<int32_t>, decltype(L::Partial())::ElementTypes>();
+    SameType<std::tuple<int32_t>, decltype(L::Partial(0))::ElementTypes>();
+  }
+  {
+    using L = Layout<int32_t, int32_t>;
+    SameType<std::tuple<int32_t, int32_t>, L::ElementTypes>();
+    SameType<std::tuple<int32_t, int32_t>, decltype(L::Partial())::ElementTypes>();
+    SameType<std::tuple<int32_t, int32_t>, decltype(L::Partial(0))::ElementTypes>();
+  }
+  {
+    using L = Layout<int8_t, int32_t, Int128>;
+    SameType<std::tuple<int8_t, int32_t, Int128>, L::ElementTypes>();
+    SameType<std::tuple<int8_t, int32_t, Int128>,
+             decltype(L::Partial())::ElementTypes>();
+    SameType<std::tuple<int8_t, int32_t, Int128>,
+             decltype(L::Partial(0))::ElementTypes>();
+    SameType<std::tuple<int8_t, int32_t, Int128>,
+             decltype(L::Partial(0, 0))::ElementTypes>();
+    SameType<std::tuple<int8_t, int32_t, Int128>,
+             decltype(L::Partial(0, 0, 0))::ElementTypes>();
+  }
+}
+
+TEST(Layout, OffsetByIndex) {
+  {
+    using L = Layout<int32_t>;
+    EXPECT_EQ(0, L::Partial().Offset<0>());
+    EXPECT_EQ(0, L::Partial(3).Offset<0>());
+    EXPECT_EQ(0, L(3).Offset<0>());
+  }
+  {
+    using L = Layout<int32_t, int32_t>;
+    EXPECT_EQ(0, L::Partial().Offset<0>());
+    EXPECT_EQ(0, L::Partial(3).Offset<0>());
+    EXPECT_EQ(12, L::Partial(3).Offset<1>());
+    EXPECT_EQ(0, L::Partial(3, 5).Offset<0>());
+    EXPECT_EQ(12, L::Partial(3, 5).Offset<1>());
+    EXPECT_EQ(0, L(3, 5).Offset<0>());
+    EXPECT_EQ(12, L(3, 5).Offset<1>());
+  }
+  {
+    using L = Layout<int8_t, int32_t, Int128>;
+    EXPECT_EQ(0, L::Partial().Offset<0>());
+    EXPECT_EQ(0, L::Partial(0).Offset<0>());
+    EXPECT_EQ(0, L::Partial(0).Offset<1>());
+    EXPECT_EQ(0, L::Partial(1).Offset<0>());
+    EXPECT_EQ(4, L::Partial(1).Offset<1>());
+    EXPECT_EQ(0, L::Partial(5).Offset<0>());
+    EXPECT_EQ(8, L::Partial(5).Offset<1>());
+    EXPECT_EQ(0, L::Partial(0, 0).Offset<0>());
+    EXPECT_EQ(0, L::Partial(0, 0).Offset<1>());
+    EXPECT_EQ(0, L::Partial(0, 0).Offset<2>());
+    EXPECT_EQ(0, L::Partial(1, 0).Offset<0>());
+    EXPECT_EQ(4, L::Partial(1, 0).Offset<1>());
+    EXPECT_EQ(8, L::Partial(1, 0).Offset<2>());
+    EXPECT_EQ(0, L::Partial(5, 3).Offset<0>());
+    EXPECT_EQ(8, L::Partial(5, 3).Offset<1>());
+    EXPECT_EQ(24, L::Partial(5, 3).Offset<2>());
+    EXPECT_EQ(0, L::Partial(0, 0, 0).Offset<0>());
+    EXPECT_EQ(0, L::Partial(0, 0, 0).Offset<1>());
+    EXPECT_EQ(0, L::Partial(0, 0, 0).Offset<2>());
+    EXPECT_EQ(0, L::Partial(1, 0, 0).Offset<0>());
+    EXPECT_EQ(4, L::Partial(1, 0, 0).Offset<1>());
+    EXPECT_EQ(8, L::Partial(1, 0, 0).Offset<2>());
+    EXPECT_EQ(0, L::Partial(5, 3, 1).Offset<0>());
+    EXPECT_EQ(24, L::Partial(5, 3, 1).Offset<2>());
+    EXPECT_EQ(8, L::Partial(5, 3, 1).Offset<1>());
+    EXPECT_EQ(0, L(5, 3, 1).Offset<0>());
+    EXPECT_EQ(24, L(5, 3, 1).Offset<2>());
+    EXPECT_EQ(8, L(5, 3, 1).Offset<1>());
+  }
+}
+
+TEST(Layout, OffsetByType) {
+  {
+    using L = Layout<int32_t>;
+    EXPECT_EQ(0, L::Partial().Offset<int32_t>());
+    EXPECT_EQ(0, L::Partial(3).Offset<int32_t>());
+    EXPECT_EQ(0, L(3).Offset<int32_t>());
+  }
+  {
+    using L = Layout<int8_t, int32_t, Int128>;
+    EXPECT_EQ(0, L::Partial().Offset<int8_t>());
+    EXPECT_EQ(0, L::Partial(0).Offset<int8_t>());
+    EXPECT_EQ(0, L::Partial(0).Offset<int32_t>());
+    EXPECT_EQ(0, L::Partial(1).Offset<int8_t>());
+    EXPECT_EQ(4, L::Partial(1).Offset<int32_t>());
+    EXPECT_EQ(0, L::Partial(5).Offset<int8_t>());
+    EXPECT_EQ(8, L::Partial(5).Offset<int32_t>());
+    EXPECT_EQ(0, L::Partial(0, 0).Offset<int8_t>());
+    EXPECT_EQ(0, L::Partial(0, 0).Offset<int32_t>());
+    EXPECT_EQ(0, L::Partial(0, 0).Offset<Int128>());
+    EXPECT_EQ(0, L::Partial(1, 0).Offset<int8_t>());
+    EXPECT_EQ(4, L::Partial(1, 0).Offset<int32_t>());
+    EXPECT_EQ(8, L::Partial(1, 0).Offset<Int128>());
+    EXPECT_EQ(0, L::Partial(5, 3).Offset<int8_t>());
+    EXPECT_EQ(8, L::Partial(5, 3).Offset<int32_t>());
+    EXPECT_EQ(24, L::Partial(5, 3).Offset<Int128>());
+    EXPECT_EQ(0, L::Partial(0, 0, 0).Offset<int8_t>());
+    EXPECT_EQ(0, L::Partial(0, 0, 0).Offset<int32_t>());
+    EXPECT_EQ(0, L::Partial(0, 0, 0).Offset<Int128>());
+    EXPECT_EQ(0, L::Partial(1, 0, 0).Offset<int8_t>());
+    EXPECT_EQ(4, L::Partial(1, 0, 0).Offset<int32_t>());
+    EXPECT_EQ(8, L::Partial(1, 0, 0).Offset<Int128>());
+    EXPECT_EQ(0, L::Partial(5, 3, 1).Offset<int8_t>());
+    EXPECT_EQ(24, L::Partial(5, 3, 1).Offset<Int128>());
+    EXPECT_EQ(8, L::Partial(5, 3, 1).Offset<int32_t>());
+    EXPECT_EQ(0, L(5, 3, 1).Offset<int8_t>());
+    EXPECT_EQ(24, L(5, 3, 1).Offset<Int128>());
+    EXPECT_EQ(8, L(5, 3, 1).Offset<int32_t>());
+  }
+}
+
+TEST(Layout, Offsets) {
+  {
+    using L = Layout<int32_t>;
+    EXPECT_THAT(L::Partial().Offsets(), ElementsAre(0));
+    EXPECT_THAT(L::Partial(3).Offsets(), ElementsAre(0));
+    EXPECT_THAT(L(3).Offsets(), ElementsAre(0));
+  }
+  {
+    using L = Layout<int32_t, int32_t>;
+    EXPECT_THAT(L::Partial().Offsets(), ElementsAre(0));
+    EXPECT_THAT(L::Partial(3).Offsets(), ElementsAre(0, 12));
+    EXPECT_THAT(L::Partial(3, 5).Offsets(), ElementsAre(0, 12));
+    EXPECT_THAT(L(3, 5).Offsets(), ElementsAre(0, 12));
+  }
+  {
+    using L = Layout<int8_t, int32_t, Int128>;
+    EXPECT_THAT(L::Partial().Offsets(), ElementsAre(0));
+    EXPECT_THAT(L::Partial(1).Offsets(), ElementsAre(0, 4));
+    EXPECT_THAT(L::Partial(5).Offsets(), ElementsAre(0, 8));
+    EXPECT_THAT(L::Partial(0, 0).Offsets(), ElementsAre(0, 0, 0));
+    EXPECT_THAT(L::Partial(1, 0).Offsets(), ElementsAre(0, 4, 8));
+    EXPECT_THAT(L::Partial(5, 3).Offsets(), ElementsAre(0, 8, 24));
+    EXPECT_THAT(L::Partial(0, 0, 0).Offsets(), ElementsAre(0, 0, 0));
+    EXPECT_THAT(L::Partial(1, 0, 0).Offsets(), ElementsAre(0, 4, 8));
+    EXPECT_THAT(L::Partial(5, 3, 1).Offsets(), ElementsAre(0, 8, 24));
+    EXPECT_THAT(L(5, 3, 1).Offsets(), ElementsAre(0, 8, 24));
+  }
+}
+
+TEST(Layout, AllocSize) {
+  {
+    using L = Layout<int32_t>;
+    EXPECT_EQ(0, L::Partial(0).AllocSize());
+    EXPECT_EQ(12, L::Partial(3).AllocSize());
+    EXPECT_EQ(12, L(3).AllocSize());
+  }
+  {
+    using L = Layout<int32_t, int32_t>;
+    EXPECT_EQ(32, L::Partial(3, 5).AllocSize());
+    EXPECT_EQ(32, L(3, 5).AllocSize());
+  }
+  {
+    using L = Layout<int8_t, int32_t, Int128>;
+    EXPECT_EQ(0, L::Partial(0, 0, 0).AllocSize());
+    EXPECT_EQ(8, L::Partial(1, 0, 0).AllocSize());
+    EXPECT_EQ(8, L::Partial(0, 1, 0).AllocSize());
+    EXPECT_EQ(16, L::Partial(0, 0, 1).AllocSize());
+    EXPECT_EQ(24, L::Partial(1, 1, 1).AllocSize());
+    EXPECT_EQ(136, L::Partial(3, 5, 7).AllocSize());
+    EXPECT_EQ(136, L(3, 5, 7).AllocSize());
+  }
+}
+
+TEST(Layout, SizeByIndex) {
+  {
+    using L = Layout<int32_t>;
+    EXPECT_EQ(0, L::Partial(0).Size<0>());
+    EXPECT_EQ(3, L::Partial(3).Size<0>());
+    EXPECT_EQ(3, L(3).Size<0>());
+  }
+  {
+    using L = Layout<int32_t, int32_t>;
+    EXPECT_EQ(0, L::Partial(0).Size<0>());
+    EXPECT_EQ(3, L::Partial(3).Size<0>());
+    EXPECT_EQ(3, L::Partial(3, 5).Size<0>());
+    EXPECT_EQ(5, L::Partial(3, 5).Size<1>());
+    EXPECT_EQ(3, L(3, 5).Size<0>());
+    EXPECT_EQ(5, L(3, 5).Size<1>());
+  }
+  {
+    using L = Layout<int8_t, int32_t, Int128>;
+    EXPECT_EQ(3, L::Partial(3).Size<0>());
+    EXPECT_EQ(3, L::Partial(3, 5).Size<0>());
+    EXPECT_EQ(5, L::Partial(3, 5).Size<1>());
+    EXPECT_EQ(3, L::Partial(3, 5, 7).Size<0>());
+    EXPECT_EQ(5, L::Partial(3, 5, 7).Size<1>());
+    EXPECT_EQ(7, L::Partial(3, 5, 7).Size<2>());
+    EXPECT_EQ(3, L(3, 5, 7).Size<0>());
+    EXPECT_EQ(5, L(3, 5, 7).Size<1>());
+    EXPECT_EQ(7, L(3, 5, 7).Size<2>());
+  }
+}
+
+TEST(Layout, SizeByType) {
+  {
+    using L = Layout<int32_t>;
+    EXPECT_EQ(0, L::Partial(0).Size<int32_t>());
+    EXPECT_EQ(3, L::Partial(3).Size<int32_t>());
+    EXPECT_EQ(3, L(3).Size<int32_t>());
+  }
+  {
+    using L = Layout<int8_t, int32_t, Int128>;
+    EXPECT_EQ(3, L::Partial(3).Size<int8_t>());
+    EXPECT_EQ(3, L::Partial(3, 5).Size<int8_t>());
+    EXPECT_EQ(5, L::Partial(3, 5).Size<int32_t>());
+    EXPECT_EQ(3, L::Partial(3, 5, 7).Size<int8_t>());
+    EXPECT_EQ(5, L::Partial(3, 5, 7).Size<int32_t>());
+    EXPECT_EQ(7, L::Partial(3, 5, 7).Size<Int128>());
+    EXPECT_EQ(3, L(3, 5, 7).Size<int8_t>());
+    EXPECT_EQ(5, L(3, 5, 7).Size<int32_t>());
+    EXPECT_EQ(7, L(3, 5, 7).Size<Int128>());
+  }
+}
+
+TEST(Layout, Sizes) {
+  {
+    using L = Layout<int32_t>;
+    EXPECT_THAT(L::Partial().Sizes(), ElementsAre());
+    EXPECT_THAT(L::Partial(3).Sizes(), ElementsAre(3));
+    EXPECT_THAT(L(3).Sizes(), ElementsAre(3));
+  }
+  {
+    using L = Layout<int32_t, int32_t>;
+    EXPECT_THAT(L::Partial().Sizes(), ElementsAre());
+    EXPECT_THAT(L::Partial(3).Sizes(), ElementsAre(3));
+    EXPECT_THAT(L::Partial(3, 5).Sizes(), ElementsAre(3, 5));
+    EXPECT_THAT(L(3, 5).Sizes(), ElementsAre(3, 5));
+  }
+  {
+    using L = Layout<int8_t, int32_t, Int128>;
+    EXPECT_THAT(L::Partial().Sizes(), ElementsAre());
+    EXPECT_THAT(L::Partial(3).Sizes(), ElementsAre(3));
+    EXPECT_THAT(L::Partial(3, 5).Sizes(), ElementsAre(3, 5));
+    EXPECT_THAT(L::Partial(3, 5, 7).Sizes(), ElementsAre(3, 5, 7));
+    EXPECT_THAT(L(3, 5, 7).Sizes(), ElementsAre(3, 5, 7));
+  }
+}
+
+TEST(Layout, PointerByIndex) {
+  alignas(max_align_t) const unsigned char p[100] = {};
+  {
+    using L = Layout<int32_t>;
+    EXPECT_EQ(0, Distance(p, Type<const int32_t*>(L::Partial().Pointer<0>(p))));
+    EXPECT_EQ(0, Distance(p, Type<const int32_t*>(L::Partial(3).Pointer<0>(p))));
+    EXPECT_EQ(0, Distance(p, Type<const int32_t*>(L(3).Pointer<0>(p))));
+  }
+  {
+    using L = Layout<int32_t, int32_t>;
+    EXPECT_EQ(0, Distance(p, Type<const int32_t*>(L::Partial().Pointer<0>(p))));
+    EXPECT_EQ(0, Distance(p, Type<const int32_t*>(L::Partial(3).Pointer<0>(p))));
+    EXPECT_EQ(12, Distance(p, Type<const int32_t*>(L::Partial(3).Pointer<1>(p))));
+    EXPECT_EQ(0,
+              Distance(p, Type<const int32_t*>(L::Partial(3, 5).Pointer<0>(p))));
+    EXPECT_EQ(12,
+              Distance(p, Type<const int32_t*>(L::Partial(3, 5).Pointer<1>(p))));
+    EXPECT_EQ(0, Distance(p, Type<const int32_t*>(L(3, 5).Pointer<0>(p))));
+    EXPECT_EQ(12, Distance(p, Type<const int32_t*>(L(3, 5).Pointer<1>(p))));
+  }
+  {
+    using L = Layout<int8_t, int32_t, Int128>;
+    EXPECT_EQ(0, Distance(p, Type<const int8_t*>(L::Partial().Pointer<0>(p))));
+    EXPECT_EQ(0, Distance(p, Type<const int8_t*>(L::Partial(0).Pointer<0>(p))));
+    EXPECT_EQ(0, Distance(p, Type<const int32_t*>(L::Partial(0).Pointer<1>(p))));
+    EXPECT_EQ(0, Distance(p, Type<const int8_t*>(L::Partial(1).Pointer<0>(p))));
+    EXPECT_EQ(4, Distance(p, Type<const int32_t*>(L::Partial(1).Pointer<1>(p))));
+    EXPECT_EQ(0, Distance(p, Type<const int8_t*>(L::Partial(5).Pointer<0>(p))));
+    EXPECT_EQ(8, Distance(p, Type<const int32_t*>(L::Partial(5).Pointer<1>(p))));
+    EXPECT_EQ(0,
+              Distance(p, Type<const int8_t*>(L::Partial(0, 0).Pointer<0>(p))));
+    EXPECT_EQ(0,
+              Distance(p, Type<const int32_t*>(L::Partial(0, 0).Pointer<1>(p))));
+    EXPECT_EQ(0,
+              Distance(p, Type<const Int128*>(L::Partial(0, 0).Pointer<2>(p))));
+    EXPECT_EQ(0,
+              Distance(p, Type<const int8_t*>(L::Partial(1, 0).Pointer<0>(p))));
+    EXPECT_EQ(4,
+              Distance(p, Type<const int32_t*>(L::Partial(1, 0).Pointer<1>(p))));
+    EXPECT_EQ(8,
+              Distance(p, Type<const Int128*>(L::Partial(1, 0).Pointer<2>(p))));
+    EXPECT_EQ(0,
+              Distance(p, Type<const int8_t*>(L::Partial(5, 3).Pointer<0>(p))));
+    EXPECT_EQ(8,
+              Distance(p, Type<const int32_t*>(L::Partial(5, 3).Pointer<1>(p))));
+    EXPECT_EQ(24,
+              Distance(p, Type<const Int128*>(L::Partial(5, 3).Pointer<2>(p))));
+    EXPECT_EQ(
+        0, Distance(p, Type<const int8_t*>(L::Partial(0, 0, 0).Pointer<0>(p))));
+    EXPECT_EQ(
+        0, Distance(p, Type<const int32_t*>(L::Partial(0, 0, 0).Pointer<1>(p))));
+    EXPECT_EQ(
+        0, Distance(p, Type<const Int128*>(L::Partial(0, 0, 0).Pointer<2>(p))));
+    EXPECT_EQ(
+        0, Distance(p, Type<const int8_t*>(L::Partial(1, 0, 0).Pointer<0>(p))));
+    EXPECT_EQ(
+        4, Distance(p, Type<const int32_t*>(L::Partial(1, 0, 0).Pointer<1>(p))));
+    EXPECT_EQ(
+        8, Distance(p, Type<const Int128*>(L::Partial(1, 0, 0).Pointer<2>(p))));
+    EXPECT_EQ(
+        0, Distance(p, Type<const int8_t*>(L::Partial(5, 3, 1).Pointer<0>(p))));
+    EXPECT_EQ(
+        24,
+        Distance(p, Type<const Int128*>(L::Partial(5, 3, 1).Pointer<2>(p))));
+    EXPECT_EQ(
+        8, Distance(p, Type<const int32_t*>(L::Partial(5, 3, 1).Pointer<1>(p))));
+    EXPECT_EQ(0, Distance(p, Type<const int8_t*>(L(5, 3, 1).Pointer<0>(p))));
+    EXPECT_EQ(24, Distance(p, Type<const Int128*>(L(5, 3, 1).Pointer<2>(p))));
+    EXPECT_EQ(8, Distance(p, Type<const int32_t*>(L(5, 3, 1).Pointer<1>(p))));
+  }
+}
+
+TEST(Layout, PointerByType) {
+  alignas(max_align_t) const unsigned char p[100] = {};
+  {
+    using L = Layout<int32_t>;
+    EXPECT_EQ(0,
+              Distance(p, Type<const int32_t*>(L::Partial().Pointer<int32_t>(p))));
+    EXPECT_EQ(0,
+              Distance(p, Type<const int32_t*>(L::Partial(3).Pointer<int32_t>(p))));
+    EXPECT_EQ(0, Distance(p, Type<const int32_t*>(L(3).Pointer<int32_t>(p))));
+  }
+  {
+    using L = Layout<int8_t, int32_t, Int128>;
+    EXPECT_EQ(0, Distance(p, Type<const int8_t*>(L::Partial().Pointer<int8_t>(p))));
+    EXPECT_EQ(0,
+              Distance(p, Type<const int8_t*>(L::Partial(0).Pointer<int8_t>(p))));
+    EXPECT_EQ(0,
+              Distance(p, Type<const int32_t*>(L::Partial(0).Pointer<int32_t>(p))));
+    EXPECT_EQ(0,
+              Distance(p, Type<const int8_t*>(L::Partial(1).Pointer<int8_t>(p))));
+    EXPECT_EQ(4,
+              Distance(p, Type<const int32_t*>(L::Partial(1).Pointer<int32_t>(p))));
+    EXPECT_EQ(0,
+              Distance(p, Type<const int8_t*>(L::Partial(5).Pointer<int8_t>(p))));
+    EXPECT_EQ(8,
+              Distance(p, Type<const int32_t*>(L::Partial(5).Pointer<int32_t>(p))));
+    EXPECT_EQ(
+        0, Distance(p, Type<const int8_t*>(L::Partial(0, 0).Pointer<int8_t>(p))));
+    EXPECT_EQ(
+        0, Distance(p, Type<const int32_t*>(L::Partial(0, 0).Pointer<int32_t>(p))));
+    EXPECT_EQ(
+        0,
+        Distance(p, Type<const Int128*>(L::Partial(0, 0).Pointer<Int128>(p))));
+    EXPECT_EQ(
+        0, Distance(p, Type<const int8_t*>(L::Partial(1, 0).Pointer<int8_t>(p))));
+    EXPECT_EQ(
+        4, Distance(p, Type<const int32_t*>(L::Partial(1, 0).Pointer<int32_t>(p))));
+    EXPECT_EQ(
+        8,
+        Distance(p, Type<const Int128*>(L::Partial(1, 0).Pointer<Int128>(p))));
+    EXPECT_EQ(
+        0, Distance(p, Type<const int8_t*>(L::Partial(5, 3).Pointer<int8_t>(p))));
+    EXPECT_EQ(
+        8, Distance(p, Type<const int32_t*>(L::Partial(5, 3).Pointer<int32_t>(p))));
+    EXPECT_EQ(
+        24,
+        Distance(p, Type<const Int128*>(L::Partial(5, 3).Pointer<Int128>(p))));
+    EXPECT_EQ(
+        0,
+        Distance(p, Type<const int8_t*>(L::Partial(0, 0, 0).Pointer<int8_t>(p))));
+    EXPECT_EQ(
+        0,
+        Distance(p, Type<const int32_t*>(L::Partial(0, 0, 0).Pointer<int32_t>(p))));
+    EXPECT_EQ(0, Distance(p, Type<const Int128*>(
+                                 L::Partial(0, 0, 0).Pointer<Int128>(p))));
+    EXPECT_EQ(
+        0,
+        Distance(p, Type<const int8_t*>(L::Partial(1, 0, 0).Pointer<int8_t>(p))));
+    EXPECT_EQ(
+        4,
+        Distance(p, Type<const int32_t*>(L::Partial(1, 0, 0).Pointer<int32_t>(p))));
+    EXPECT_EQ(8, Distance(p, Type<const Int128*>(
+                                 L::Partial(1, 0, 0).Pointer<Int128>(p))));
+    EXPECT_EQ(
+        0,
+        Distance(p, Type<const int8_t*>(L::Partial(5, 3, 1).Pointer<int8_t>(p))));
+    EXPECT_EQ(24, Distance(p, Type<const Int128*>(
+                                  L::Partial(5, 3, 1).Pointer<Int128>(p))));
+    EXPECT_EQ(
+        8,
+        Distance(p, Type<const int32_t*>(L::Partial(5, 3, 1).Pointer<int32_t>(p))));
+    EXPECT_EQ(24,
+              Distance(p, Type<const Int128*>(L(5, 3, 1).Pointer<Int128>(p))));
+    EXPECT_EQ(8, Distance(p, Type<const int32_t*>(L(5, 3, 1).Pointer<int32_t>(p))));
+  }
+}
+
+TEST(Layout, MutablePointerByIndex) {
+  alignas(max_align_t) unsigned char p[100];
+  {
+    using L = Layout<int32_t>;
+    EXPECT_EQ(0, Distance(p, Type<int32_t*>(L::Partial().Pointer<0>(p))));
+    EXPECT_EQ(0, Distance(p, Type<int32_t*>(L::Partial(3).Pointer<0>(p))));
+    EXPECT_EQ(0, Distance(p, Type<int32_t*>(L(3).Pointer<0>(p))));
+  }
+  {
+    using L = Layout<int32_t, int32_t>;
+    EXPECT_EQ(0, Distance(p, Type<int32_t*>(L::Partial().Pointer<0>(p))));
+    EXPECT_EQ(0, Distance(p, Type<int32_t*>(L::Partial(3).Pointer<0>(p))));
+    EXPECT_EQ(12, Distance(p, Type<int32_t*>(L::Partial(3).Pointer<1>(p))));
+    EXPECT_EQ(0, Distance(p, Type<int32_t*>(L::Partial(3, 5).Pointer<0>(p))));
+    EXPECT_EQ(12, Distance(p, Type<int32_t*>(L::Partial(3, 5).Pointer<1>(p))));
+    EXPECT_EQ(0, Distance(p, Type<int32_t*>(L(3, 5).Pointer<0>(p))));
+    EXPECT_EQ(12, Distance(p, Type<int32_t*>(L(3, 5).Pointer<1>(p))));
+  }
+  {
+    using L = Layout<int8_t, int32_t, Int128>;
+    EXPECT_EQ(0, Distance(p, Type<int8_t*>(L::Partial().Pointer<0>(p))));
+    EXPECT_EQ(0, Distance(p, Type<int8_t*>(L::Partial(0).Pointer<0>(p))));
+    EXPECT_EQ(0, Distance(p, Type<int32_t*>(L::Partial(0).Pointer<1>(p))));
+    EXPECT_EQ(0, Distance(p, Type<int8_t*>(L::Partial(1).Pointer<0>(p))));
+    EXPECT_EQ(4, Distance(p, Type<int32_t*>(L::Partial(1).Pointer<1>(p))));
+    EXPECT_EQ(0, Distance(p, Type<int8_t*>(L::Partial(5).Pointer<0>(p))));
+    EXPECT_EQ(8, Distance(p, Type<int32_t*>(L::Partial(5).Pointer<1>(p))));
+    EXPECT_EQ(0, Distance(p, Type<int8_t*>(L::Partial(0, 0).Pointer<0>(p))));
+    EXPECT_EQ(0, Distance(p, Type<int32_t*>(L::Partial(0, 0).Pointer<1>(p))));
+    EXPECT_EQ(0, Distance(p, Type<Int128*>(L::Partial(0, 0).Pointer<2>(p))));
+    EXPECT_EQ(0, Distance(p, Type<int8_t*>(L::Partial(1, 0).Pointer<0>(p))));
+    EXPECT_EQ(4, Distance(p, Type<int32_t*>(L::Partial(1, 0).Pointer<1>(p))));
+    EXPECT_EQ(8, Distance(p, Type<Int128*>(L::Partial(1, 0).Pointer<2>(p))));
+    EXPECT_EQ(0, Distance(p, Type<int8_t*>(L::Partial(5, 3).Pointer<0>(p))));
+    EXPECT_EQ(8, Distance(p, Type<int32_t*>(L::Partial(5, 3).Pointer<1>(p))));
+    EXPECT_EQ(24, Distance(p, Type<Int128*>(L::Partial(5, 3).Pointer<2>(p))));
+    EXPECT_EQ(0, Distance(p, Type<int8_t*>(L::Partial(0, 0, 0).Pointer<0>(p))));
+    EXPECT_EQ(0, Distance(p, Type<int32_t*>(L::Partial(0, 0, 0).Pointer<1>(p))));
+    EXPECT_EQ(0, Distance(p, Type<Int128*>(L::Partial(0, 0, 0).Pointer<2>(p))));
+    EXPECT_EQ(0, Distance(p, Type<int8_t*>(L::Partial(1, 0, 0).Pointer<0>(p))));
+    EXPECT_EQ(4, Distance(p, Type<int32_t*>(L::Partial(1, 0, 0).Pointer<1>(p))));
+    EXPECT_EQ(8, Distance(p, Type<Int128*>(L::Partial(1, 0, 0).Pointer<2>(p))));
+    EXPECT_EQ(0, Distance(p, Type<int8_t*>(L::Partial(5, 3, 1).Pointer<0>(p))));
+    EXPECT_EQ(24,
+              Distance(p, Type<Int128*>(L::Partial(5, 3, 1).Pointer<2>(p))));
+    EXPECT_EQ(8, Distance(p, Type<int32_t*>(L::Partial(5, 3, 1).Pointer<1>(p))));
+    EXPECT_EQ(0, Distance(p, Type<int8_t*>(L(5, 3, 1).Pointer<0>(p))));
+    EXPECT_EQ(24, Distance(p, Type<Int128*>(L(5, 3, 1).Pointer<2>(p))));
+    EXPECT_EQ(8, Distance(p, Type<int32_t*>(L(5, 3, 1).Pointer<1>(p))));
+  }
+}
+
+TEST(Layout, MutablePointerByType) {
+  alignas(max_align_t) unsigned char p[100];
+  {
+    using L = Layout<int32_t>;
+    EXPECT_EQ(0, Distance(p, Type<int32_t*>(L::Partial().Pointer<int32_t>(p))));
+    EXPECT_EQ(0, Distance(p, Type<int32_t*>(L::Partial(3).Pointer<int32_t>(p))));
+    EXPECT_EQ(0, Distance(p, Type<int32_t*>(L(3).Pointer<int32_t>(p))));
+  }
+  {
+    using L = Layout<int8_t, int32_t, Int128>;
+    EXPECT_EQ(0, Distance(p, Type<int8_t*>(L::Partial().Pointer<int8_t>(p))));
+    EXPECT_EQ(0, Distance(p, Type<int8_t*>(L::Partial(0).Pointer<int8_t>(p))));
+    EXPECT_EQ(0, Distance(p, Type<int32_t*>(L::Partial(0).Pointer<int32_t>(p))));
+    EXPECT_EQ(0, Distance(p, Type<int8_t*>(L::Partial(1).Pointer<int8_t>(p))));
+    EXPECT_EQ(4, Distance(p, Type<int32_t*>(L::Partial(1).Pointer<int32_t>(p))));
+    EXPECT_EQ(0, Distance(p, Type<int8_t*>(L::Partial(5).Pointer<int8_t>(p))));
+    EXPECT_EQ(8, Distance(p, Type<int32_t*>(L::Partial(5).Pointer<int32_t>(p))));
+    EXPECT_EQ(0, Distance(p, Type<int8_t*>(L::Partial(0, 0).Pointer<int8_t>(p))));
+    EXPECT_EQ(0, Distance(p, Type<int32_t*>(L::Partial(0, 0).Pointer<int32_t>(p))));
+    EXPECT_EQ(0,
+              Distance(p, Type<Int128*>(L::Partial(0, 0).Pointer<Int128>(p))));
+    EXPECT_EQ(0, Distance(p, Type<int8_t*>(L::Partial(1, 0).Pointer<int8_t>(p))));
+    EXPECT_EQ(4, Distance(p, Type<int32_t*>(L::Partial(1, 0).Pointer<int32_t>(p))));
+    EXPECT_EQ(8,
+              Distance(p, Type<Int128*>(L::Partial(1, 0).Pointer<Int128>(p))));
+    EXPECT_EQ(0, Distance(p, Type<int8_t*>(L::Partial(5, 3).Pointer<int8_t>(p))));
+    EXPECT_EQ(8, Distance(p, Type<int32_t*>(L::Partial(5, 3).Pointer<int32_t>(p))));
+    EXPECT_EQ(24,
+              Distance(p, Type<Int128*>(L::Partial(5, 3).Pointer<Int128>(p))));
+    EXPECT_EQ(0,
+              Distance(p, Type<int8_t*>(L::Partial(0, 0, 0).Pointer<int8_t>(p))));
+    EXPECT_EQ(0,
+              Distance(p, Type<int32_t*>(L::Partial(0, 0, 0).Pointer<int32_t>(p))));
+    EXPECT_EQ(
+        0, Distance(p, Type<Int128*>(L::Partial(0, 0, 0).Pointer<Int128>(p))));
+    EXPECT_EQ(0,
+              Distance(p, Type<int8_t*>(L::Partial(1, 0, 0).Pointer<int8_t>(p))));
+    EXPECT_EQ(4,
+              Distance(p, Type<int32_t*>(L::Partial(1, 0, 0).Pointer<int32_t>(p))));
+    EXPECT_EQ(
+        8, Distance(p, Type<Int128*>(L::Partial(1, 0, 0).Pointer<Int128>(p))));
+    EXPECT_EQ(0,
+              Distance(p, Type<int8_t*>(L::Partial(5, 3, 1).Pointer<int8_t>(p))));
+    EXPECT_EQ(
+        24, Distance(p, Type<Int128*>(L::Partial(5, 3, 1).Pointer<Int128>(p))));
+    EXPECT_EQ(8,
+              Distance(p, Type<int32_t*>(L::Partial(5, 3, 1).Pointer<int32_t>(p))));
+    EXPECT_EQ(0, Distance(p, Type<int8_t*>(L(5, 3, 1).Pointer<int8_t>(p))));
+    EXPECT_EQ(24, Distance(p, Type<Int128*>(L(5, 3, 1).Pointer<Int128>(p))));
+    EXPECT_EQ(8, Distance(p, Type<int32_t*>(L(5, 3, 1).Pointer<int32_t>(p))));
+  }
+}
+
+TEST(Layout, Pointers) {
+  alignas(max_align_t) const unsigned char p[100] = {};
+  using L = Layout<int8_t, int8_t, Int128>;
+  {
+    const auto x = L::Partial();
+    EXPECT_EQ(std::make_tuple(x.Pointer<0>(p)),
+              Type<std::tuple<const int8_t*>>(x.Pointers(p)));
+  }
+  {
+    const auto x = L::Partial(1);
+    EXPECT_EQ(std::make_tuple(x.Pointer<0>(p), x.Pointer<1>(p)),
+              (Type<std::tuple<const int8_t*, const int8_t*>>(x.Pointers(p))));
+  }
+  {
+    const auto x = L::Partial(1, 2);
+    EXPECT_EQ(
+        std::make_tuple(x.Pointer<0>(p), x.Pointer<1>(p), x.Pointer<2>(p)),
+        (Type<std::tuple<const int8_t*, const int8_t*, const Int128*>>(
+            x.Pointers(p))));
+  }
+  {
+    const auto x = L::Partial(1, 2, 3);
+    EXPECT_EQ(
+        std::make_tuple(x.Pointer<0>(p), x.Pointer<1>(p), x.Pointer<2>(p)),
+        (Type<std::tuple<const int8_t*, const int8_t*, const Int128*>>(
+            x.Pointers(p))));
+  }
+  {
+    const L x(1, 2, 3);
+    EXPECT_EQ(
+        std::make_tuple(x.Pointer<0>(p), x.Pointer<1>(p), x.Pointer<2>(p)),
+        (Type<std::tuple<const int8_t*, const int8_t*, const Int128*>>(
+            x.Pointers(p))));
+  }
+}
+
+TEST(Layout, MutablePointers) {
+  alignas(max_align_t) unsigned char p[100];
+  using L = Layout<int8_t, int8_t, Int128>;
+  {
+    const auto x = L::Partial();
+    EXPECT_EQ(std::make_tuple(x.Pointer<0>(p)),
+              Type<std::tuple<int8_t*>>(x.Pointers(p)));
+  }
+  {
+    const auto x = L::Partial(1);
+    EXPECT_EQ(std::make_tuple(x.Pointer<0>(p), x.Pointer<1>(p)),
+              (Type<std::tuple<int8_t*, int8_t*>>(x.Pointers(p))));
+  }
+  {
+    const auto x = L::Partial(1, 2);
+    EXPECT_EQ(
+        std::make_tuple(x.Pointer<0>(p), x.Pointer<1>(p), x.Pointer<2>(p)),
+        (Type<std::tuple<int8_t*, int8_t*, Int128*>>(x.Pointers(p))));
+  }
+  {
+    const auto x = L::Partial(1, 2, 3);
+    EXPECT_EQ(
+        std::make_tuple(x.Pointer<0>(p), x.Pointer<1>(p), x.Pointer<2>(p)),
+        (Type<std::tuple<int8_t*, int8_t*, Int128*>>(x.Pointers(p))));
+  }
+  {
+    const L x(1, 2, 3);
+    EXPECT_EQ(
+        std::make_tuple(x.Pointer<0>(p), x.Pointer<1>(p), x.Pointer<2>(p)),
+        (Type<std::tuple<int8_t*, int8_t*, Int128*>>(x.Pointers(p))));
+  }
+}
+
+TEST(Layout, SliceByIndexSize) {
+  alignas(max_align_t) const unsigned char p[100] = {};
+  {
+    using L = Layout<int32_t>;
+    EXPECT_EQ(0, L::Partial(0).Slice<0>(p).size());
+    EXPECT_EQ(3, L::Partial(3).Slice<0>(p).size());
+    EXPECT_EQ(3, L(3).Slice<0>(p).size());
+  }
+  {
+    using L = Layout<int32_t, int32_t>;
+    EXPECT_EQ(3, L::Partial(3).Slice<0>(p).size());
+    EXPECT_EQ(5, L::Partial(3, 5).Slice<1>(p).size());
+    EXPECT_EQ(5, L(3, 5).Slice<1>(p).size());
+  }
+  {
+    using L = Layout<int8_t, int32_t, Int128>;
+    EXPECT_EQ(3, L::Partial(3).Slice<0>(p).size());
+    EXPECT_EQ(3, L::Partial(3, 5).Slice<0>(p).size());
+    EXPECT_EQ(5, L::Partial(3, 5).Slice<1>(p).size());
+    EXPECT_EQ(3, L::Partial(3, 5, 7).Slice<0>(p).size());
+    EXPECT_EQ(5, L::Partial(3, 5, 7).Slice<1>(p).size());
+    EXPECT_EQ(7, L::Partial(3, 5, 7).Slice<2>(p).size());
+    EXPECT_EQ(3, L(3, 5, 7).Slice<0>(p).size());
+    EXPECT_EQ(5, L(3, 5, 7).Slice<1>(p).size());
+    EXPECT_EQ(7, L(3, 5, 7).Slice<2>(p).size());
+  }
+}
+
+TEST(Layout, SliceByTypeSize) {
+  alignas(max_align_t) const unsigned char p[100] = {};
+  {
+    using L = Layout<int32_t>;
+    EXPECT_EQ(0, L::Partial(0).Slice<int32_t>(p).size());
+    EXPECT_EQ(3, L::Partial(3).Slice<int32_t>(p).size());
+    EXPECT_EQ(3, L(3).Slice<int32_t>(p).size());
+  }
+  {
+    using L = Layout<int8_t, int32_t, Int128>;
+    EXPECT_EQ(3, L::Partial(3).Slice<int8_t>(p).size());
+    EXPECT_EQ(3, L::Partial(3, 5).Slice<int8_t>(p).size());
+    EXPECT_EQ(5, L::Partial(3, 5).Slice<int32_t>(p).size());
+    EXPECT_EQ(3, L::Partial(3, 5, 7).Slice<int8_t>(p).size());
+    EXPECT_EQ(5, L::Partial(3, 5, 7).Slice<int32_t>(p).size());
+    EXPECT_EQ(7, L::Partial(3, 5, 7).Slice<Int128>(p).size());
+    EXPECT_EQ(3, L(3, 5, 7).Slice<int8_t>(p).size());
+    EXPECT_EQ(5, L(3, 5, 7).Slice<int32_t>(p).size());
+    EXPECT_EQ(7, L(3, 5, 7).Slice<Int128>(p).size());
+  }
+}
+
+TEST(Layout, MutableSliceByIndexSize) {
+  alignas(max_align_t) unsigned char p[100];
+  {
+    using L = Layout<int32_t>;
+    EXPECT_EQ(0, L::Partial(0).Slice<0>(p).size());
+    EXPECT_EQ(3, L::Partial(3).Slice<0>(p).size());
+    EXPECT_EQ(3, L(3).Slice<0>(p).size());
+  }
+  {
+    using L = Layout<int32_t, int32_t>;
+    EXPECT_EQ(3, L::Partial(3).Slice<0>(p).size());
+    EXPECT_EQ(5, L::Partial(3, 5).Slice<1>(p).size());
+    EXPECT_EQ(5, L(3, 5).Slice<1>(p).size());
+  }
+  {
+    using L = Layout<int8_t, int32_t, Int128>;
+    EXPECT_EQ(3, L::Partial(3).Slice<0>(p).size());
+    EXPECT_EQ(3, L::Partial(3, 5).Slice<0>(p).size());
+    EXPECT_EQ(5, L::Partial(3, 5).Slice<1>(p).size());
+    EXPECT_EQ(3, L::Partial(3, 5, 7).Slice<0>(p).size());
+    EXPECT_EQ(5, L::Partial(3, 5, 7).Slice<1>(p).size());
+    EXPECT_EQ(7, L::Partial(3, 5, 7).Slice<2>(p).size());
+    EXPECT_EQ(3, L(3, 5, 7).Slice<0>(p).size());
+    EXPECT_EQ(5, L(3, 5, 7).Slice<1>(p).size());
+    EXPECT_EQ(7, L(3, 5, 7).Slice<2>(p).size());
+  }
+}
+
+TEST(Layout, MutableSliceByTypeSize) {
+  alignas(max_align_t) unsigned char p[100];
+  {
+    using L = Layout<int32_t>;
+    EXPECT_EQ(0, L::Partial(0).Slice<int32_t>(p).size());
+    EXPECT_EQ(3, L::Partial(3).Slice<int32_t>(p).size());
+    EXPECT_EQ(3, L(3).Slice<int32_t>(p).size());
+  }
+  {
+    using L = Layout<int8_t, int32_t, Int128>;
+    EXPECT_EQ(3, L::Partial(3).Slice<int8_t>(p).size());
+    EXPECT_EQ(3, L::Partial(3, 5).Slice<int8_t>(p).size());
+    EXPECT_EQ(5, L::Partial(3, 5).Slice<int32_t>(p).size());
+    EXPECT_EQ(3, L::Partial(3, 5, 7).Slice<int8_t>(p).size());
+    EXPECT_EQ(5, L::Partial(3, 5, 7).Slice<int32_t>(p).size());
+    EXPECT_EQ(7, L::Partial(3, 5, 7).Slice<Int128>(p).size());
+    EXPECT_EQ(3, L(3, 5, 7).Slice<int8_t>(p).size());
+    EXPECT_EQ(5, L(3, 5, 7).Slice<int32_t>(p).size());
+    EXPECT_EQ(7, L(3, 5, 7).Slice<Int128>(p).size());
+  }
+}
+
+TEST(Layout, SliceByIndexData) {
+  alignas(max_align_t) const unsigned char p[100] = {};
+  {
+    using L = Layout<int32_t>;
+    EXPECT_EQ(
+        0,
+        Distance(p, Type<Span<const int32_t>>(L::Partial(0).Slice<0>(p)).data()));
+    EXPECT_EQ(
+        0,
+        Distance(p, Type<Span<const int32_t>>(L::Partial(3).Slice<0>(p)).data()));
+    EXPECT_EQ(0, Distance(p, Type<Span<const int32_t>>(L(3).Slice<0>(p)).data()));
+  }
+  {
+    using L = Layout<int32_t, int32_t>;
+    EXPECT_EQ(
+        0,
+        Distance(p, Type<Span<const int32_t>>(L::Partial(3).Slice<0>(p)).data()));
+    EXPECT_EQ(
+        0,
+        Distance(p,
+                 Type<Span<const int32_t>>(L::Partial(3, 5).Slice<0>(p)).data()));
+    EXPECT_EQ(
+        12,
+        Distance(p,
+                 Type<Span<const int32_t>>(L::Partial(3, 5).Slice<1>(p)).data()));
+    EXPECT_EQ(0,
+              Distance(p, Type<Span<const int32_t>>(L(3, 5).Slice<0>(p)).data()));
+    EXPECT_EQ(12,
+              Distance(p, Type<Span<const int32_t>>(L(3, 5).Slice<1>(p)).data()));
+  }
+  {
+    using L = Layout<int8_t, int32_t, Int128>;
+    EXPECT_EQ(
+        0,
+        Distance(p, Type<Span<const int8_t>>(L::Partial(0).Slice<0>(p)).data()));
+    EXPECT_EQ(
+        0,
+        Distance(p, Type<Span<const int8_t>>(L::Partial(1).Slice<0>(p)).data()));
+    EXPECT_EQ(
+        0,
+        Distance(p, Type<Span<const int8_t>>(L::Partial(5).Slice<0>(p)).data()));
+    EXPECT_EQ(
+        0, Distance(
+               p, Type<Span<const int8_t>>(L::Partial(0, 0).Slice<0>(p)).data()));
+    EXPECT_EQ(
+        0,
+        Distance(p,
+                 Type<Span<const int32_t>>(L::Partial(0, 0).Slice<1>(p)).data()));
+    EXPECT_EQ(
+        0, Distance(
+               p, Type<Span<const int8_t>>(L::Partial(1, 0).Slice<0>(p)).data()));
+    EXPECT_EQ(
+        4,
+        Distance(p,
+                 Type<Span<const int32_t>>(L::Partial(1, 0).Slice<1>(p)).data()));
+    EXPECT_EQ(
+        0, Distance(
+               p, Type<Span<const int8_t>>(L::Partial(5, 3).Slice<0>(p)).data()));
+    EXPECT_EQ(
+        8,
+        Distance(p,
+                 Type<Span<const int32_t>>(L::Partial(5, 3).Slice<1>(p)).data()));
+    EXPECT_EQ(
+        0,
+        Distance(
+            p, Type<Span<const int8_t>>(L::Partial(0, 0, 0).Slice<0>(p)).data()));
+    EXPECT_EQ(
+        0,
+        Distance(
+            p,
+            Type<Span<const int32_t>>(L::Partial(0, 0, 0).Slice<1>(p)).data()));
+    EXPECT_EQ(
+        0,
+        Distance(
+            p,
+            Type<Span<const Int128>>(L::Partial(0, 0, 0).Slice<2>(p)).data()));
+    EXPECT_EQ(
+        0,
+        Distance(
+            p, Type<Span<const int8_t>>(L::Partial(1, 0, 0).Slice<0>(p)).data()));
+    EXPECT_EQ(
+        4,
+        Distance(
+            p,
+            Type<Span<const int32_t>>(L::Partial(1, 0, 0).Slice<1>(p)).data()));
+    EXPECT_EQ(
+        8,
+        Distance(
+            p,
+            Type<Span<const Int128>>(L::Partial(1, 0, 0).Slice<2>(p)).data()));
+    EXPECT_EQ(
+        0,
+        Distance(
+            p, Type<Span<const int8_t>>(L::Partial(5, 3, 1).Slice<0>(p)).data()));
+    EXPECT_EQ(
+        24,
+        Distance(
+            p,
+            Type<Span<const Int128>>(L::Partial(5, 3, 1).Slice<2>(p)).data()));
+    EXPECT_EQ(
+        8,
+        Distance(
+            p,
+            Type<Span<const int32_t>>(L::Partial(5, 3, 1).Slice<1>(p)).data()));
+    EXPECT_EQ(
+        0, Distance(p, Type<Span<const int8_t>>(L(5, 3, 1).Slice<0>(p)).data()));
+    EXPECT_EQ(
+        24,
+        Distance(p, Type<Span<const Int128>>(L(5, 3, 1).Slice<2>(p)).data()));
+    EXPECT_EQ(
+        8, Distance(p, Type<Span<const int32_t>>(L(5, 3, 1).Slice<1>(p)).data()));
+  }
+}
+
+TEST(Layout, SliceByTypeData) {
+  alignas(max_align_t) const unsigned char p[100] = {};
+  {
+    using L = Layout<int32_t>;
+    EXPECT_EQ(
+        0,
+        Distance(
+            p, Type<Span<const int32_t>>(L::Partial(0).Slice<int32_t>(p)).data()));
+    EXPECT_EQ(
+        0,
+        Distance(
+            p, Type<Span<const int32_t>>(L::Partial(3).Slice<int32_t>(p)).data()));
+    EXPECT_EQ(
+        0, Distance(p, Type<Span<const int32_t>>(L(3).Slice<int32_t>(p)).data()));
+  }
+  {
+    using L = Layout<int8_t, int32_t, Int128>;
+    EXPECT_EQ(
+        0, Distance(
+               p, Type<Span<const int8_t>>(L::Partial(0).Slice<int8_t>(p)).data()));
+    EXPECT_EQ(
+        0, Distance(
+               p, Type<Span<const int8_t>>(L::Partial(1).Slice<int8_t>(p)).data()));
+    EXPECT_EQ(
+        0, Distance(
+               p, Type<Span<const int8_t>>(L::Partial(5).Slice<int8_t>(p)).data()));
+    EXPECT_EQ(
+        0,
+        Distance(
+            p, Type<Span<const int8_t>>(L::Partial(0, 0).Slice<int8_t>(p)).data()));
+    EXPECT_EQ(
+        0,
+        Distance(
+            p,
+            Type<Span<const int32_t>>(L::Partial(0, 0).Slice<int32_t>(p)).data()));
+    EXPECT_EQ(
+        0,
+        Distance(
+            p, Type<Span<const int8_t>>(L::Partial(1, 0).Slice<int8_t>(p)).data()));
+    EXPECT_EQ(
+        4,
+        Distance(
+            p,
+            Type<Span<const int32_t>>(L::Partial(1, 0).Slice<int32_t>(p)).data()));
+    EXPECT_EQ(
+        0,
+        Distance(
+            p, Type<Span<const int8_t>>(L::Partial(5, 3).Slice<int8_t>(p)).data()));
+    EXPECT_EQ(
+        8,
+        Distance(
+            p,
+            Type<Span<const int32_t>>(L::Partial(5, 3).Slice<int32_t>(p)).data()));
+    EXPECT_EQ(
+        0,
+        Distance(
+            p,
+            Type<Span<const int8_t>>(L::Partial(0, 0, 0).Slice<int8_t>(p)).data()));
+    EXPECT_EQ(
+        0,
+        Distance(p, Type<Span<const int32_t>>(L::Partial(0, 0, 0).Slice<int32_t>(p))
+                        .data()));
+    EXPECT_EQ(0, Distance(p, Type<Span<const Int128>>(
+                                 L::Partial(0, 0, 0).Slice<Int128>(p))
+                                 .data()));
+    EXPECT_EQ(
+        0,
+        Distance(
+            p,
+            Type<Span<const int8_t>>(L::Partial(1, 0, 0).Slice<int8_t>(p)).data()));
+    EXPECT_EQ(
+        4,
+        Distance(p, Type<Span<const int32_t>>(L::Partial(1, 0, 0).Slice<int32_t>(p))
+                        .data()));
+    EXPECT_EQ(8, Distance(p, Type<Span<const Int128>>(
+                                 L::Partial(1, 0, 0).Slice<Int128>(p))
+                                 .data()));
+    EXPECT_EQ(
+        0,
+        Distance(
+            p,
+            Type<Span<const int8_t>>(L::Partial(5, 3, 1).Slice<int8_t>(p)).data()));
+    EXPECT_EQ(24, Distance(p, Type<Span<const Int128>>(
+                                  L::Partial(5, 3, 1).Slice<Int128>(p))
+                                  .data()));
+    EXPECT_EQ(
+        8,
+        Distance(p, Type<Span<const int32_t>>(L::Partial(5, 3, 1).Slice<int32_t>(p))
+                        .data()));
+    EXPECT_EQ(
+        0,
+        Distance(p, Type<Span<const int8_t>>(L(5, 3, 1).Slice<int8_t>(p)).data()));
+    EXPECT_EQ(
+        24,
+        Distance(p,
+                 Type<Span<const Int128>>(L(5, 3, 1).Slice<Int128>(p)).data()));
+    EXPECT_EQ(
+        8, Distance(
+               p, Type<Span<const int32_t>>(L(5, 3, 1).Slice<int32_t>(p)).data()));
+  }
+}
+
+TEST(Layout, MutableSliceByIndexData) {
+  alignas(max_align_t) unsigned char p[100];
+  {
+    using L = Layout<int32_t>;
+    EXPECT_EQ(0,
+              Distance(p, Type<Span<int32_t>>(L::Partial(0).Slice<0>(p)).data()));
+    EXPECT_EQ(0,
+              Distance(p, Type<Span<int32_t>>(L::Partial(3).Slice<0>(p)).data()));
+    EXPECT_EQ(0, Distance(p, Type<Span<int32_t>>(L(3).Slice<0>(p)).data()));
+  }
+  {
+    using L = Layout<int32_t, int32_t>;
+    EXPECT_EQ(0,
+              Distance(p, Type<Span<int32_t>>(L::Partial(3).Slice<0>(p)).data()));
+    EXPECT_EQ(
+        0, Distance(p, Type<Span<int32_t>>(L::Partial(3, 5).Slice<0>(p)).data()));
+    EXPECT_EQ(
+        12,
+        Distance(p, Type<Span<int32_t>>(L::Partial(3, 5).Slice<1>(p)).data()));
+    EXPECT_EQ(0, Distance(p, Type<Span<int32_t>>(L(3, 5).Slice<0>(p)).data()));
+    EXPECT_EQ(12, Distance(p, Type<Span<int32_t>>(L(3, 5).Slice<1>(p)).data()));
+  }
+  {
+    using L = Layout<int8_t, int32_t, Int128>;
+    EXPECT_EQ(0,
+              Distance(p, Type<Span<int8_t>>(L::Partial(0).Slice<0>(p)).data()));
+    EXPECT_EQ(0,
+              Distance(p, Type<Span<int8_t>>(L::Partial(1).Slice<0>(p)).data()));
+    EXPECT_EQ(0,
+              Distance(p, Type<Span<int8_t>>(L::Partial(5).Slice<0>(p)).data()));
+    EXPECT_EQ(
+        0, Distance(p, Type<Span<int8_t>>(L::Partial(0, 0).Slice<0>(p)).data()));
+    EXPECT_EQ(
+        0, Distance(p, Type<Span<int32_t>>(L::Partial(0, 0).Slice<1>(p)).data()));
+    EXPECT_EQ(
+        0, Distance(p, Type<Span<int8_t>>(L::Partial(1, 0).Slice<0>(p)).data()));
+    EXPECT_EQ(
+        4, Distance(p, Type<Span<int32_t>>(L::Partial(1, 0).Slice<1>(p)).data()));
+    EXPECT_EQ(
+        0, Distance(p, Type<Span<int8_t>>(L::Partial(5, 3).Slice<0>(p)).data()));
+    EXPECT_EQ(
+        8, Distance(p, Type<Span<int32_t>>(L::Partial(5, 3).Slice<1>(p)).data()));
+    EXPECT_EQ(
+        0,
+        Distance(p, Type<Span<int8_t>>(L::Partial(0, 0, 0).Slice<0>(p)).data()));
+    EXPECT_EQ(
+        0,
+        Distance(p, Type<Span<int32_t>>(L::Partial(0, 0, 0).Slice<1>(p)).data()));
+    EXPECT_EQ(
+        0, Distance(
+               p, Type<Span<Int128>>(L::Partial(0, 0, 0).Slice<2>(p)).data()));
+    EXPECT_EQ(
+        0,
+        Distance(p, Type<Span<int8_t>>(L::Partial(1, 0, 0).Slice<0>(p)).data()));
+    EXPECT_EQ(
+        4,
+        Distance(p, Type<Span<int32_t>>(L::Partial(1, 0, 0).Slice<1>(p)).data()));
+    EXPECT_EQ(
+        8, Distance(
+               p, Type<Span<Int128>>(L::Partial(1, 0, 0).Slice<2>(p)).data()));
+    EXPECT_EQ(
+        0,
+        Distance(p, Type<Span<int8_t>>(L::Partial(5, 3, 1).Slice<0>(p)).data()));
+    EXPECT_EQ(
+        24, Distance(
+                p, Type<Span<Int128>>(L::Partial(5, 3, 1).Slice<2>(p)).data()));
+    EXPECT_EQ(
+        8,
+        Distance(p, Type<Span<int32_t>>(L::Partial(5, 3, 1).Slice<1>(p)).data()));
+    EXPECT_EQ(0, Distance(p, Type<Span<int8_t>>(L(5, 3, 1).Slice<0>(p)).data()));
+    EXPECT_EQ(24,
+              Distance(p, Type<Span<Int128>>(L(5, 3, 1).Slice<2>(p)).data()));
+    EXPECT_EQ(8, Distance(p, Type<Span<int32_t>>(L(5, 3, 1).Slice<1>(p)).data()));
+  }
+}
+
+TEST(Layout, MutableSliceByTypeData) {
+  alignas(max_align_t) unsigned char p[100];
+  {
+    using L = Layout<int32_t>;
+    EXPECT_EQ(
+        0,
+        Distance(p, Type<Span<int32_t>>(L::Partial(0).Slice<int32_t>(p)).data()));
+    EXPECT_EQ(
+        0,
+        Distance(p, Type<Span<int32_t>>(L::Partial(3).Slice<int32_t>(p)).data()));
+    EXPECT_EQ(0, Distance(p, Type<Span<int32_t>>(L(3).Slice<int32_t>(p)).data()));
+  }
+  {
+    using L = Layout<int8_t, int32_t, Int128>;
+    EXPECT_EQ(
+        0, Distance(p, Type<Span<int8_t>>(L::Partial(0).Slice<int8_t>(p)).data()));
+    EXPECT_EQ(
+        0, Distance(p, Type<Span<int8_t>>(L::Partial(1).Slice<int8_t>(p)).data()));
+    EXPECT_EQ(
+        0, Distance(p, Type<Span<int8_t>>(L::Partial(5).Slice<int8_t>(p)).data()));
+    EXPECT_EQ(
+        0,
+        Distance(p, Type<Span<int8_t>>(L::Partial(0, 0).Slice<int8_t>(p)).data()));
+    EXPECT_EQ(
+        0, Distance(
+               p, Type<Span<int32_t>>(L::Partial(0, 0).Slice<int32_t>(p)).data()));
+    EXPECT_EQ(
+        0,
+        Distance(p, Type<Span<int8_t>>(L::Partial(1, 0).Slice<int8_t>(p)).data()));
+    EXPECT_EQ(
+        4, Distance(
+               p, Type<Span<int32_t>>(L::Partial(1, 0).Slice<int32_t>(p)).data()));
+    EXPECT_EQ(
+        0,
+        Distance(p, Type<Span<int8_t>>(L::Partial(5, 3).Slice<int8_t>(p)).data()));
+    EXPECT_EQ(
+        8, Distance(
+               p, Type<Span<int32_t>>(L::Partial(5, 3).Slice<int32_t>(p)).data()));
+    EXPECT_EQ(
+        0, Distance(
+               p, Type<Span<int8_t>>(L::Partial(0, 0, 0).Slice<int8_t>(p)).data()));
+    EXPECT_EQ(
+        0,
+        Distance(
+            p, Type<Span<int32_t>>(L::Partial(0, 0, 0).Slice<int32_t>(p)).data()));
+    EXPECT_EQ(
+        0,
+        Distance(
+            p,
+            Type<Span<Int128>>(L::Partial(0, 0, 0).Slice<Int128>(p)).data()));
+    EXPECT_EQ(
+        0, Distance(
+               p, Type<Span<int8_t>>(L::Partial(1, 0, 0).Slice<int8_t>(p)).data()));
+    EXPECT_EQ(
+        4,
+        Distance(
+            p, Type<Span<int32_t>>(L::Partial(1, 0, 0).Slice<int32_t>(p)).data()));
+    EXPECT_EQ(
+        8,
+        Distance(
+            p,
+            Type<Span<Int128>>(L::Partial(1, 0, 0).Slice<Int128>(p)).data()));
+    EXPECT_EQ(
+        0, Distance(
+               p, Type<Span<int8_t>>(L::Partial(5, 3, 1).Slice<int8_t>(p)).data()));
+    EXPECT_EQ(
+        24,
+        Distance(
+            p,
+            Type<Span<Int128>>(L::Partial(5, 3, 1).Slice<Int128>(p)).data()));
+    EXPECT_EQ(
+        8,
+        Distance(
+            p, Type<Span<int32_t>>(L::Partial(5, 3, 1).Slice<int32_t>(p)).data()));
+    EXPECT_EQ(0,
+              Distance(p, Type<Span<int8_t>>(L(5, 3, 1).Slice<int8_t>(p)).data()));
+    EXPECT_EQ(
+        24,
+        Distance(p, Type<Span<Int128>>(L(5, 3, 1).Slice<Int128>(p)).data()));
+    EXPECT_EQ(
+        8, Distance(p, Type<Span<int32_t>>(L(5, 3, 1).Slice<int32_t>(p)).data()));
+  }
+}
+
+MATCHER_P(IsSameSlice, slice, "") {
+  return arg.size() == slice.size() && arg.data() == slice.data();
+}
+
+template <typename... M>
+class TupleMatcher {
+ public:
+  explicit TupleMatcher(M... matchers) : matchers_(std::move(matchers)...) {}
+
+  template <typename Tuple>
+  bool MatchAndExplain(const Tuple& p,
+                       testing::MatchResultListener* /* listener */) const {
+    static_assert(std::tuple_size<Tuple>::value == sizeof...(M), "");
+    return MatchAndExplainImpl(
+        p, absl::make_index_sequence<std::tuple_size<Tuple>::value>{});
+  }
+
+  // For the matcher concept. Left empty as we don't really need the diagnostics
+  // right now.
+  void DescribeTo(::std::ostream* os) const {}
+  void DescribeNegationTo(::std::ostream* os) const {}
+
+ private:
+  template <typename Tuple, size_t... Is>
+  bool MatchAndExplainImpl(const Tuple& p, absl::index_sequence<Is...>) const {
+    // Using std::min as a simple variadic "and".
+    return std::min(
+        {true, testing::SafeMatcherCast<
+                   const typename std::tuple_element<Is, Tuple>::type&>(
+                   std::get<Is>(matchers_))
+                   .Matches(std::get<Is>(p))...});
+  }
+
+  std::tuple<M...> matchers_;
+};
+
+template <typename... M>
+testing::PolymorphicMatcher<TupleMatcher<M...>> Tuple(M... matchers) {
+  return testing::MakePolymorphicMatcher(
+      TupleMatcher<M...>(std::move(matchers)...));
+}
+
+TEST(Layout, Slices) {
+  alignas(max_align_t) const unsigned char p[100] = {};
+  using L = Layout<int8_t, int8_t, Int128>;
+  {
+    const auto x = L::Partial();
+    EXPECT_THAT(Type<std::tuple<>>(x.Slices(p)), Tuple());
+  }
+  {
+    const auto x = L::Partial(1);
+    EXPECT_THAT(Type<std::tuple<Span<const int8_t>>>(x.Slices(p)),
+                Tuple(IsSameSlice(x.Slice<0>(p))));
+  }
+  {
+    const auto x = L::Partial(1, 2);
+    EXPECT_THAT(
+        (Type<std::tuple<Span<const int8_t>, Span<const int8_t>>>(x.Slices(p))),
+        Tuple(IsSameSlice(x.Slice<0>(p)), IsSameSlice(x.Slice<1>(p))));
+  }
+  {
+    const auto x = L::Partial(1, 2, 3);
+    EXPECT_THAT((Type<std::tuple<Span<const int8_t>, Span<const int8_t>,
+                                 Span<const Int128>>>(x.Slices(p))),
+                Tuple(IsSameSlice(x.Slice<0>(p)), IsSameSlice(x.Slice<1>(p)),
+                      IsSameSlice(x.Slice<2>(p))));
+  }
+  {
+    const L x(1, 2, 3);
+    EXPECT_THAT((Type<std::tuple<Span<const int8_t>, Span<const int8_t>,
+                                 Span<const Int128>>>(x.Slices(p))),
+                Tuple(IsSameSlice(x.Slice<0>(p)), IsSameSlice(x.Slice<1>(p)),
+                      IsSameSlice(x.Slice<2>(p))));
+  }
+}
+
+TEST(Layout, MutableSlices) {
+  alignas(max_align_t) unsigned char p[100] = {};
+  using L = Layout<int8_t, int8_t, Int128>;
+  {
+    const auto x = L::Partial();
+    EXPECT_THAT(Type<std::tuple<>>(x.Slices(p)), Tuple());
+  }
+  {
+    const auto x = L::Partial(1);
+    EXPECT_THAT(Type<std::tuple<Span<int8_t>>>(x.Slices(p)),
+                Tuple(IsSameSlice(x.Slice<0>(p))));
+  }
+  {
+    const auto x = L::Partial(1, 2);
+    EXPECT_THAT((Type<std::tuple<Span<int8_t>, Span<int8_t>>>(x.Slices(p))),
+                Tuple(IsSameSlice(x.Slice<0>(p)), IsSameSlice(x.Slice<1>(p))));
+  }
+  {
+    const auto x = L::Partial(1, 2, 3);
+    EXPECT_THAT(
+        (Type<std::tuple<Span<int8_t>, Span<int8_t>, Span<Int128>>>(x.Slices(p))),
+        Tuple(IsSameSlice(x.Slice<0>(p)), IsSameSlice(x.Slice<1>(p)),
+              IsSameSlice(x.Slice<2>(p))));
+  }
+  {
+    const L x(1, 2, 3);
+    EXPECT_THAT(
+        (Type<std::tuple<Span<int8_t>, Span<int8_t>, Span<Int128>>>(x.Slices(p))),
+        Tuple(IsSameSlice(x.Slice<0>(p)), IsSameSlice(x.Slice<1>(p)),
+              IsSameSlice(x.Slice<2>(p))));
+  }
+}
+
+TEST(Layout, UnalignedTypes) {
+  constexpr Layout<unsigned char, unsigned char, unsigned char> x(1, 2, 3);
+  alignas(max_align_t) unsigned char p[x.AllocSize() + 1];
+  EXPECT_THAT(x.Pointers(p + 1), Tuple(p + 1, p + 2, p + 4));
+}
+
+TEST(Layout, CustomAlignment) {
+  constexpr Layout<unsigned char, Aligned<unsigned char, 8>> x(1, 2);
+  alignas(max_align_t) unsigned char p[x.AllocSize()];
+  EXPECT_EQ(10, x.AllocSize());
+  EXPECT_THAT(x.Pointers(p), Tuple(p + 0, p + 8));
+}
+
+TEST(Layout, OverAligned) {
+  constexpr size_t M = alignof(max_align_t);
+  constexpr Layout<unsigned char, Aligned<unsigned char, 2 * M>> x(1, 3);
+  alignas(2 * M) unsigned char p[x.AllocSize()];
+  EXPECT_EQ(2 * M + 3, x.AllocSize());
+  EXPECT_THAT(x.Pointers(p), Tuple(p + 0, p + 2 * M));
+}
+
+TEST(Layout, Alignment) {
+  static_assert(Layout<int8_t>::Alignment() == 1, "");
+  static_assert(Layout<int32_t>::Alignment() == 4, "");
+  static_assert(Layout<int64_t>::Alignment() == 8, "");
+  static_assert(Layout<Aligned<int8_t, 64>>::Alignment() == 64, "");
+  static_assert(Layout<int8_t, int32_t, int64_t>::Alignment() == 8, "");
+  static_assert(Layout<int8_t, int64_t, int32_t>::Alignment() == 8, "");
+  static_assert(Layout<int32_t, int8_t, int64_t>::Alignment() == 8, "");
+  static_assert(Layout<int32_t, int64_t, int8_t>::Alignment() == 8, "");
+  static_assert(Layout<int64_t, int8_t, int32_t>::Alignment() == 8, "");
+  static_assert(Layout<int64_t, int32_t, int8_t>::Alignment() == 8, "");
+}
+
+TEST(Layout, ConstexprPartial) {
+  constexpr size_t M = alignof(max_align_t);
+  constexpr Layout<unsigned char, Aligned<unsigned char, 2 * M>> x(1, 3);
+  static_assert(x.Partial(1).template Offset<1>() == 2 * M, "");
+}
+// [from, to)
+struct Region {
+  size_t from;
+  size_t to;
+};
+
+void ExpectRegionPoisoned(const unsigned char* p, size_t n, bool poisoned) {
+#ifdef ADDRESS_SANITIZER
+  for (size_t i = 0; i != n; ++i) {
+    EXPECT_EQ(poisoned, __asan_address_is_poisoned(p + i));
+  }
+#endif
+}
+
+template <size_t N>
+void ExpectPoisoned(const unsigned char (&buf)[N],
+                    std::initializer_list<Region> reg) {
+  size_t prev = 0;
+  for (const Region& r : reg) {
+    ExpectRegionPoisoned(buf + prev, r.from - prev, false);
+    ExpectRegionPoisoned(buf + r.from, r.to - r.from, true);
+    prev = r.to;
+  }
+  ExpectRegionPoisoned(buf + prev, N - prev, false);
+}
+
+TEST(Layout, PoisonPadding) {
+  using L = Layout<int8_t, int64_t, int32_t, Int128>;
+
+  constexpr size_t n = L::Partial(1, 2, 3, 4).AllocSize();
+  {
+    constexpr auto x = L::Partial();
+    alignas(max_align_t) const unsigned char c[n] = {};
+    x.PoisonPadding(c);
+    EXPECT_EQ(x.Slices(c), x.Slices(c));
+    ExpectPoisoned(c, {});
+  }
+  {
+    constexpr auto x = L::Partial(1);
+    alignas(max_align_t) const unsigned char c[n] = {};
+    x.PoisonPadding(c);
+    EXPECT_EQ(x.Slices(c), x.Slices(c));
+    ExpectPoisoned(c, {{1, 8}});
+  }
+  {
+    constexpr auto x = L::Partial(1, 2);
+    alignas(max_align_t) const unsigned char c[n] = {};
+    x.PoisonPadding(c);
+    EXPECT_EQ(x.Slices(c), x.Slices(c));
+    ExpectPoisoned(c, {{1, 8}});
+  }
+  {
+    constexpr auto x = L::Partial(1, 2, 3);
+    alignas(max_align_t) const unsigned char c[n] = {};
+    x.PoisonPadding(c);
+    EXPECT_EQ(x.Slices(c), x.Slices(c));
+    ExpectPoisoned(c, {{1, 8}, {36, 40}});
+  }
+  {
+    constexpr auto x = L::Partial(1, 2, 3, 4);
+    alignas(max_align_t) const unsigned char c[n] = {};
+    x.PoisonPadding(c);
+    EXPECT_EQ(x.Slices(c), x.Slices(c));
+    ExpectPoisoned(c, {{1, 8}, {36, 40}});
+  }
+  {
+    constexpr L x(1, 2, 3, 4);
+    alignas(max_align_t) const unsigned char c[n] = {};
+    x.PoisonPadding(c);
+    EXPECT_EQ(x.Slices(c), x.Slices(c));
+    ExpectPoisoned(c, {{1, 8}, {36, 40}});
+  }
+}
+
+TEST(Layout, DebugString) {
+  const std::string int64_type =
+#ifdef _MSC_VER
+  "__int64";
+#else   // _MSC_VER
+  std::is_same<int64_t, long long>::value ? "long long" : "long";  // NOLINT
+#endif  // _MSC_VER
+  {
+    constexpr auto x = Layout<int8_t, int32_t, int8_t, Int128>::Partial();
+    EXPECT_EQ("@0<signed char>(1)", x.DebugString());
+  }
+  {
+    constexpr auto x = Layout<int8_t, int32_t, int8_t, Int128>::Partial(1);
+    EXPECT_EQ("@0<signed char>(1)[1]; @4<int>(4)", x.DebugString());
+  }
+  {
+    constexpr auto x = Layout<int8_t, int32_t, int8_t, Int128>::Partial(1, 2);
+    EXPECT_EQ("@0<signed char>(1)[1]; @4<int>(4)[2]; @12<signed char>(1)",
+              x.DebugString());
+  }
+  {
+    constexpr auto x = Layout<int8_t, int32_t, int8_t, Int128>::Partial(1, 2, 3);
+    EXPECT_EQ(
+        "@0<signed char>(1)[1]; @4<int>(4)[2]; @12<signed char>(1)[3]; "
+        "@16<" +
+            int64_type + " [2]>(16)",
+        x.DebugString());
+  }
+  {
+    constexpr auto x = Layout<int8_t, int32_t, int8_t, Int128>::Partial(1, 2, 3, 4);
+    EXPECT_EQ(
+        "@0<signed char>(1)[1]; @4<int>(4)[2]; @12<signed char>(1)[3]; "
+        "@16<" +
+            int64_type + " [2]>(16)[4]",
+        x.DebugString());
+  }
+  {
+    constexpr Layout<int8_t, int32_t, int8_t, Int128> x(1, 2, 3, 4);
+    EXPECT_EQ(
+        "@0<signed char>(1)[1]; @4<int>(4)[2]; @12<signed char>(1)[3]; "
+        "@16<" +
+            int64_type + " [2]>(16)[4]",
+        x.DebugString());
+  }
+}
+
+TEST(Layout, CharTypes) {
+  constexpr Layout<int32_t> x(1);
+  alignas(max_align_t) char c[x.AllocSize()] = {};
+  alignas(max_align_t) unsigned char uc[x.AllocSize()] = {};
+  alignas(max_align_t) signed char sc[x.AllocSize()] = {};
+  alignas(max_align_t) const char cc[x.AllocSize()] = {};
+  alignas(max_align_t) const unsigned char cuc[x.AllocSize()] = {};
+  alignas(max_align_t) const signed char csc[x.AllocSize()] = {};
+
+  Type<int32_t*>(x.Pointer<0>(c));
+  Type<int32_t*>(x.Pointer<0>(uc));
+  Type<int32_t*>(x.Pointer<0>(sc));
+  Type<const int32_t*>(x.Pointer<0>(cc));
+  Type<const int32_t*>(x.Pointer<0>(cuc));
+  Type<const int32_t*>(x.Pointer<0>(csc));
+
+  Type<int32_t*>(x.Pointer<int32_t>(c));
+  Type<int32_t*>(x.Pointer<int32_t>(uc));
+  Type<int32_t*>(x.Pointer<int32_t>(sc));
+  Type<const int32_t*>(x.Pointer<int32_t>(cc));
+  Type<const int32_t*>(x.Pointer<int32_t>(cuc));
+  Type<const int32_t*>(x.Pointer<int32_t>(csc));
+
+  Type<std::tuple<int32_t*>>(x.Pointers(c));
+  Type<std::tuple<int32_t*>>(x.Pointers(uc));
+  Type<std::tuple<int32_t*>>(x.Pointers(sc));
+  Type<std::tuple<const int32_t*>>(x.Pointers(cc));
+  Type<std::tuple<const int32_t*>>(x.Pointers(cuc));
+  Type<std::tuple<const int32_t*>>(x.Pointers(csc));
+
+  Type<Span<int32_t>>(x.Slice<0>(c));
+  Type<Span<int32_t>>(x.Slice<0>(uc));
+  Type<Span<int32_t>>(x.Slice<0>(sc));
+  Type<Span<const int32_t>>(x.Slice<0>(cc));
+  Type<Span<const int32_t>>(x.Slice<0>(cuc));
+  Type<Span<const int32_t>>(x.Slice<0>(csc));
+
+  Type<std::tuple<Span<int32_t>>>(x.Slices(c));
+  Type<std::tuple<Span<int32_t>>>(x.Slices(uc));
+  Type<std::tuple<Span<int32_t>>>(x.Slices(sc));
+  Type<std::tuple<Span<const int32_t>>>(x.Slices(cc));
+  Type<std::tuple<Span<const int32_t>>>(x.Slices(cuc));
+  Type<std::tuple<Span<const int32_t>>>(x.Slices(csc));
+}
+
+TEST(Layout, ConstElementType) {
+  constexpr Layout<const int32_t> x(1);
+  alignas(int32_t) char c[x.AllocSize()] = {};
+  const char* cc = c;
+  const int32_t* p = reinterpret_cast<const int32_t*>(cc);
+
+  EXPECT_EQ(alignof(int32_t), x.Alignment());
+
+  EXPECT_EQ(0, x.Offset<0>());
+  EXPECT_EQ(0, x.Offset<const int32_t>());
+
+  EXPECT_THAT(x.Offsets(), ElementsAre(0));
+
+  EXPECT_EQ(1, x.Size<0>());
+  EXPECT_EQ(1, x.Size<const int32_t>());
+
+  EXPECT_THAT(x.Sizes(), ElementsAre(1));
+
+  EXPECT_EQ(sizeof(int32_t), x.AllocSize());
+
+  EXPECT_EQ(p, Type<const int32_t*>(x.Pointer<0>(c)));
+  EXPECT_EQ(p, Type<const int32_t*>(x.Pointer<0>(cc)));
+
+  EXPECT_EQ(p, Type<const int32_t*>(x.Pointer<const int32_t>(c)));
+  EXPECT_EQ(p, Type<const int32_t*>(x.Pointer<const int32_t>(cc)));
+
+  EXPECT_THAT(Type<std::tuple<const int32_t*>>(x.Pointers(c)), Tuple(p));
+  EXPECT_THAT(Type<std::tuple<const int32_t*>>(x.Pointers(cc)), Tuple(p));
+
+  EXPECT_THAT(Type<Span<const int32_t>>(x.Slice<0>(c)),
+              IsSameSlice(Span<const int32_t>(p, 1)));
+  EXPECT_THAT(Type<Span<const int32_t>>(x.Slice<0>(cc)),
+              IsSameSlice(Span<const int32_t>(p, 1)));
+
+  EXPECT_THAT(Type<Span<const int32_t>>(x.Slice<const int32_t>(c)),
+              IsSameSlice(Span<const int32_t>(p, 1)));
+  EXPECT_THAT(Type<Span<const int32_t>>(x.Slice<const int32_t>(cc)),
+              IsSameSlice(Span<const int32_t>(p, 1)));
+
+  EXPECT_THAT(Type<std::tuple<Span<const int32_t>>>(x.Slices(c)),
+              Tuple(IsSameSlice(Span<const int32_t>(p, 1))));
+  EXPECT_THAT(Type<std::tuple<Span<const int32_t>>>(x.Slices(cc)),
+              Tuple(IsSameSlice(Span<const int32_t>(p, 1))));
+}
+
+namespace example {
+
+// Immutable move-only string with sizeof equal to sizeof(void*). The string
+// size and the characters are kept in the same heap allocation.
+class CompactString {
+ public:
+  CompactString(const char* s = "") {  // NOLINT
+    const size_t size = strlen(s);
+    // size_t[1], followed by char[size + 1].
+    // This statement doesn't allocate memory.
+    const L layout(1, size + 1);
+    // AllocSize() tells us how much memory we need to allocate for all our
+    // data.
+    p_.reset(new unsigned char[layout.AllocSize()]);
+    // If running under ASAN, mark the padding bytes, if any, to catch memory
+    // errors.
+    layout.PoisonPadding(p_.get());
+    // Store the size in the allocation.
+    // Pointer<size_t>() is a synonym for Pointer<0>().
+    *layout.Pointer<size_t>(p_.get()) = size;
+    // Store the characters in the allocation.
+    memcpy(layout.Pointer<char>(p_.get()), s, size + 1);
+  }
+
+  size_t size() const {
+    // Equivalent to reinterpret_cast<size_t&>(*p).
+    return *L::Partial().Pointer<size_t>(p_.get());
+  }
+
+  const char* c_str() const {
+    // Equivalent to reinterpret_cast<char*>(p.get() + sizeof(size_t)).
+    // The argument in Partial(1) specifies that we have size_t[1] in front of
+    // the
+    // characters.
+    return L::Partial(1).Pointer<char>(p_.get());
+  }
+
+ private:
+  // Our heap allocation contains a size_t followed by an array of chars.
+  using L = Layout<size_t, char>;
+  std::unique_ptr<unsigned char[]> p_;
+};
+
+TEST(CompactString, Works) {
+  CompactString s = "hello";
+  EXPECT_EQ(5, s.size());
+  EXPECT_STREQ("hello", s.c_str());
+}
+
+}  // namespace example
+
+}  // namespace
+}  // namespace container_internal
+}  // namespace absl