add safe_cast

Author: lukevalenty

include/safe.hpp

@@ -8,5 +8,6 @@
 #include <safe/int.hpp>
 #include <safe/match.hpp>
 #include <safe/object.hpp>
+#include <safe/safe_cast.hpp>
 #include <safe/value.hpp>
 #include <safe/var.hpp>

include/safe/detail/fwd.hpp

@@ -37,12 +37,12 @@ template <typename T> struct unsafe_cast_ferry {
 
 template <typename T>
     requires(safe::Var<T>)
-[[nodiscard]] constexpr auto unsafe_cast(auto const &src) {
+[[nodiscard]] SAFE_INLINE constexpr auto unsafe_cast(auto const &src) {
     return T{safe::unsafe_cast_ferry{src}};
 }
 
 template <typename T>
     requires(!safe::Var<T>)
-[[nodiscard]] constexpr auto unsafe_cast(auto const &src) {
+[[nodiscard]] SAFE_INLINE constexpr auto unsafe_cast(auto const &src) {
     return src;
 }

include/safe/safe_cast.hpp

@@ -0,0 +1,17 @@
+#pragma once
+
+#include <safe/detail/concepts.hpp>
+#include <safe/detail/fwd.hpp>
+#include <safe/var.hpp>
+
+#include <concepts>
+
+template <typename To, safe::Var From>
+    requires(std::is_convertible_v<typename From::value_type, To>)
+[[nodiscard]] SAFE_INLINE constexpr To safe_cast(From const &src) {
+    static_assert(safe::detail::integral_type<To>::requirement >=
+                      From::requirement,
+                  "The safe value must fit within the target value type.");
+
+    return static_cast<To>(src.unsafe_value_);
+}

test/safe/CMakeLists.txt

@@ -1,5 +1,6 @@
 add_subdirectory(array)
 add_subdirectory(var)
+add_subdirectory(safe_cast)
 
 function(add_test_suites)
     foreach(test_file ${ARGN})
@@ -34,6 +35,7 @@ add_test_suites(
     var.cpp
     match.cpp
     array.cpp
+    safe_cast.cpp
     dsl/add.cpp
     dsl/divide.cpp
     dsl/intersection.cpp

test/safe/safe_cast.cpp

@@ -0,0 +1,33 @@
+#include "gmock/gmock.h"
+#include "gtest/gtest.h"
+
+#include <cstdint>
+#include <type_traits>
+
+#include <safe.hpp>
+
+using ::testing::_;
+using ::testing::InSequence;
+using ::testing::Return;
+
+using namespace safe::interval_types;
+using namespace safe::int_types;
+using namespace safe::literals;
+
+TEST(safe_cast_test, cast_same_type) {
+    auto v = safe_cast<std::int32_t>(42_s32);
+    EXPECT_EQ(v, 42);
+    static_assert(std::is_same_v<std::int32_t, decltype(v)>);
+}
+
+TEST(safe_cast_test, cast_narrower_type) {
+    auto v = safe_cast<std::uint8_t>(42_s32);
+    EXPECT_EQ(v, 42);
+    static_assert(std::is_same_v<std::uint8_t, decltype(v)>);
+}
+
+TEST(safe_cast_test, cast_different_sign) {
+    auto v = safe_cast<std::uint32_t>(99_s32);
+    EXPECT_EQ(v, 99);
+    static_assert(std::is_same_v<std::uint32_t, decltype(v)>);
+}

test/safe/safe_cast/CMakeLists.txt

@@ -0,0 +1,9 @@
+function(add_fail_tests)
+    foreach(name ${ARGN})
+        add_compile_fail_test("${name}.cpp" LIBRARIES safe_arithmetic)
+    endforeach()
+endfunction()
+
+add_fail_tests(
+    incompatible_sign_cast
+    incompatible_range_cast)

test/safe/safe_cast/incompatible_range_cast.cpp

@@ -0,0 +1,9 @@
+#include <cstdint>
+
+#include <safe.hpp>
+
+using namespace safe::interval_types;
+using namespace safe::int_types;
+using namespace safe::literals;
+
+auto main() -> int { auto v = safe_cast<std::uint8_t>(420_u32); }

test/safe/safe_cast/incompatible_sign_cast.cpp

@@ -0,0 +1,9 @@
+#include <cstdint>
+
+#include <safe.hpp>
+
+using namespace safe::interval_types;
+using namespace safe::int_types;
+using namespace safe::literals;
+
+auto main() -> int { auto v = safe_cast<std::uint32_t>(-99_s32); }