From 2cb9f4f2515cc3f6ddaf1806630114118dddf4b5 Mon Sep 17 00:00:00 2001
From: Patrick Roberts <git@patrickroberts.dev>
Date: Sat, 8 Feb 2025 14:06:16 -0600
Subject: [PATCH] Add some constexpr tests

---
 .../beman/any_view/detail/any_iterator.hpp    |  3 +-
 include/beman/any_view/detail/concepts.hpp    |  2 +-
 .../any_view/detail/intrusive_small_ptr.hpp   |  2 +-
 .../any_view/detail/iterator_adaptor.hpp      |  6 ++-
 .../beman/any_view/detail/view_adaptor.hpp    |  7 +++
 tests/beman/any_view/CMakeLists.txt           |  1 +
 tests/beman/any_view/constexpr.test.cpp       | 54 +++++++++++++++++++
 7 files changed, 71 insertions(+), 4 deletions(-)
 create mode 100644 tests/beman/any_view/constexpr.test.cpp

diff --git a/include/beman/any_view/detail/any_iterator.hpp b/include/beman/any_view/detail/any_iterator.hpp
index fda8b87..81b0041 100644
--- a/include/beman/any_view/detail/any_iterator.hpp
+++ b/include/beman/any_view/detail/any_iterator.hpp
@@ -152,7 +152,8 @@ class any_iterator {
     constexpr auto operator-=(difference_type offset) -> any_iterator&
         requires random_access
     {
-        *iterator_ptr -= offset;
+        // TODO: should virtual function for operator-= be provided to avoid signed overflow for max difference type?
+        *this += -offset;
         return *this;
     }
 
diff --git a/include/beman/any_view/detail/concepts.hpp b/include/beman/any_view/detail/concepts.hpp
index 0e071f7..f25cbe8 100644
--- a/include/beman/any_view/detail/concepts.hpp
+++ b/include/beman/any_view/detail/concepts.hpp
@@ -34,7 +34,7 @@ concept contiguous_iterator_compatible_with =
     random_access_iterator_compatible_with<IterT, IterConceptT> and
     (not std::derived_from<IterConceptT, std::contiguous_iterator_tag> or std::contiguous_iterator<IterT>);
 
-template <class RangeRefT, class TraitsRefT, class IterConceptT>
+template <class RangeRefT, class TraitsRefT, class IterConceptT = std::contiguous_iterator_tag>
 concept contiguous_reference_convertible_to =
     std::convertible_to<RangeRefT, TraitsRefT> and
     (not std::derived_from<IterConceptT, std::contiguous_iterator_tag> or
diff --git a/include/beman/any_view/detail/intrusive_small_ptr.hpp b/include/beman/any_view/detail/intrusive_small_ptr.hpp
index 9ba0f56..896da9c 100644
--- a/include/beman/any_view/detail/intrusive_small_ptr.hpp
+++ b/include/beman/any_view/detail/intrusive_small_ptr.hpp
@@ -77,7 +77,7 @@ class intrusive_small_ptr {
         if (index == index_type::is_inplace) {
             other.get_inplace()->copy_to(&inplace);
         } else {
-            pointer = other.pointer->copy();
+            pointer = other ? other.pointer->copy() : nullptr;
         }
     }
 
diff --git a/include/beman/any_view/detail/iterator_adaptor.hpp b/include/beman/any_view/detail/iterator_adaptor.hpp
index 3893a2c..8e93520 100644
--- a/include/beman/any_view/detail/iterator_adaptor.hpp
+++ b/include/beman/any_view/detail/iterator_adaptor.hpp
@@ -3,6 +3,7 @@
 #ifndef BEMAN_ANY_VIEW_DETAIL_ITERATOR_ADAPTOR_HPP
 #define BEMAN_ANY_VIEW_DETAIL_ITERATOR_ADAPTOR_HPP
 
+#include <beman/any_view/detail/concepts.hpp>
 #include <beman/any_view/detail/iterator_interface.hpp>
 #include <beman/any_view/detail/utility.hpp>
 
@@ -71,7 +72,7 @@ class iterator_adaptor : public iterator_interface<ElementT, RefT, RValueRefT, D
     [[nodiscard]] constexpr auto iter_move() const -> RValueRefT override { return std::ranges::iter_move(iterator); }
 
     [[nodiscard]] constexpr auto operator->() const -> pointer override {
-        if constexpr (contiguous) {
+        if constexpr (contiguous and contiguous_reference_convertible_to<std::iter_reference_t<IteratorT>, RefT>) {
             return std::to_address(iterator);
         } else {
             unreachable();
@@ -129,6 +130,9 @@ class iterator_adaptor : public iterator_interface<ElementT, RefT, RValueRefT, D
     [[nodiscard]] constexpr auto operator==(std::default_sentinel_t) const -> bool override {
         return iterator == sentinel;
     }
+
+    // ICE workaround for GCC
+    constexpr ~iterator_adaptor() noexcept override {}
 };
 
 } // namespace beman::any_view::detail
diff --git a/include/beman/any_view/detail/view_adaptor.hpp b/include/beman/any_view/detail/view_adaptor.hpp
index efbcc31..b3f81a1 100644
--- a/include/beman/any_view/detail/view_adaptor.hpp
+++ b/include/beman/any_view/detail/view_adaptor.hpp
@@ -23,6 +23,10 @@ class view_adaptor : public view_interface<IterConceptT, ElementT, RefT, RValueR
   public:
     constexpr view_adaptor(ViewT&& view) noexcept(get_noexcept()) : view(std::move(view)) {}
 
+    constexpr view_adaptor(const view_adaptor&) = default;
+
+    constexpr view_adaptor(view_adaptor&&) noexcept = default;
+
     auto copy_to(void* destination) const -> void override {
         if constexpr (std::copy_constructible<ViewT>) {
             ::new (destination) view_adaptor(*this);
@@ -62,6 +66,9 @@ class view_adaptor : public view_interface<IterConceptT, ElementT, RefT, RValueR
             unreachable();
         }
     }
+
+    // ICE workaround for GCC
+    constexpr ~view_adaptor() noexcept override {}
 };
 
 } // namespace beman::any_view::detail
diff --git a/tests/beman/any_view/CMakeLists.txt b/tests/beman/any_view/CMakeLists.txt
index 556512d..40d5263 100644
--- a/tests/beman/any_view/CMakeLists.txt
+++ b/tests/beman/any_view/CMakeLists.txt
@@ -10,5 +10,6 @@ function(beman_add_test)
 endfunction()
 
 beman_add_test(TARGET concepts SOURCES concepts.test.cpp)
+beman_add_test(TARGET constexpr SOURCES constexpr.test.cpp)
 beman_add_test(TARGET sfinae SOURCES sfinae.test.cpp)
 beman_add_test(TARGET type_traits SOURCES type_traits.test.cpp)
diff --git a/tests/beman/any_view/constexpr.test.cpp b/tests/beman/any_view/constexpr.test.cpp
new file mode 100644
index 0000000..d6a9fff
--- /dev/null
+++ b/tests/beman/any_view/constexpr.test.cpp
@@ -0,0 +1,54 @@
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+
+#include <beman/any_view/any_view.hpp>
+
+#include <gtest/gtest.h>
+
+#include <vector>
+
+using beman::any_view::any_view;
+
+#if BEMAN_ANY_VIEW_USE_ENUM()
+using enum beman::any_view::any_view_options;
+
+template <class ValueT>
+using proxy_any_view = any_view<ValueT, input, ValueT>;
+#elif BEMAN_ANY_VIEW_USE_TRAITS()
+template <class ValueT>
+struct proxy_traits {
+    using reference_type = ValueT;
+};
+
+template <class ValueT>
+using proxy_any_view = any_view<ValueT, proxy_traits<ValueT>>;
+#elif BEMAN_ANY_VIEW_USE_NAMED()
+using beman::any_view::type;
+
+template <class ValueT>
+using proxy_any_view = any_view<ValueT, {.reference_type = type<ValueT>}>;
+#endif
+
+constexpr auto sum(proxy_any_view<proxy_any_view<int>> views) {
+    auto result = 0;
+
+    for (auto view : views) {
+        for (const auto value : view) {
+            result += value;
+        }
+    }
+
+    return result;
+}
+
+TEST(ConstexprTest, sum_vector_of_vector) {
+    static_assert(15 == sum(std::vector{std::vector{1, 2}, std::vector{3, 4}, std::vector{5}}));
+    EXPECT_EQ(15, sum(std::vector{std::vector{1, 2}, std::vector{3, 4}, std::vector{5}}));
+}
+
+TEST(ConstexprTest, sum_transform_view_of_iota) {
+    constexpr auto iota = [](int n) { return std::views::iota(1) | std::views::take(n); };
+    constexpr auto view = iota(5) | std::views::transform(iota);
+
+    static_assert(35 == sum(view));
+    EXPECT_EQ(35, sum(view));
+}