From 36f70ff8c6342d2f5fddd9b1d98e3cca5fec1e6f Mon Sep 17 00:00:00 2001
From: Luke Valenty <luke.valenty@intel.com>
Date: Thu, 15 Feb 2024 07:10:07 -0800
Subject: [PATCH] add safe_cast

---
 include/safe.hpp                              |  1 +
 include/safe/detail/fwd.hpp                   |  4 +--
 include/safe/safe_cast.hpp                    | 17 ++++++++++
 test/safe/CMakeLists.txt                      |  2 ++
 test/safe/safe_cast.cpp                       | 33 +++++++++++++++++++
 test/safe/safe_cast/CMakeLists.txt            |  9 +++++
 .../safe_cast/incompatible_range_cast.cpp     |  9 +++++
 .../safe/safe_cast/incompatible_sign_cast.cpp |  9 +++++
 8 files changed, 82 insertions(+), 2 deletions(-)
 create mode 100644 include/safe/safe_cast.hpp
 create mode 100644 test/safe/safe_cast.cpp
 create mode 100644 test/safe/safe_cast/CMakeLists.txt
 create mode 100644 test/safe/safe_cast/incompatible_range_cast.cpp
 create mode 100644 test/safe/safe_cast/incompatible_sign_cast.cpp

diff --git a/include/safe.hpp b/include/safe.hpp
index 3722100..3b63ab9 100644
--- a/include/safe.hpp
+++ b/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>
diff --git a/include/safe/detail/fwd.hpp b/include/safe/detail/fwd.hpp
index 4aa5da5..9f19fdd 100644
--- a/include/safe/detail/fwd.hpp
+++ b/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;
 }
diff --git a/include/safe/safe_cast.hpp b/include/safe/safe_cast.hpp
new file mode 100644
index 0000000..978f501
--- /dev/null
+++ b/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_);
+}
diff --git a/test/safe/CMakeLists.txt b/test/safe/CMakeLists.txt
index 3b9c18c..12389d4 100644
--- a/test/safe/CMakeLists.txt
+++ b/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
diff --git a/test/safe/safe_cast.cpp b/test/safe/safe_cast.cpp
new file mode 100644
index 0000000..bf3fe00
--- /dev/null
+++ b/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)>);
+}
diff --git a/test/safe/safe_cast/CMakeLists.txt b/test/safe/safe_cast/CMakeLists.txt
new file mode 100644
index 0000000..600dd41
--- /dev/null
+++ b/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)
diff --git a/test/safe/safe_cast/incompatible_range_cast.cpp b/test/safe/safe_cast/incompatible_range_cast.cpp
new file mode 100644
index 0000000..cec363d
--- /dev/null
+++ b/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); }
diff --git a/test/safe/safe_cast/incompatible_sign_cast.cpp b/test/safe/safe_cast/incompatible_sign_cast.cpp
new file mode 100644
index 0000000..8a3b50b
--- /dev/null
+++ b/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); }