range size() is constexpr

rollbear · Feb 22, 2024 · 33f3af8 · 33f3af8
1 parent dec4909
commit 33f3af8
Show file tree

Hide file tree

Showing 2 changed files with 18 additions and 1 deletion.
diff --git a/include/strong_type/range.hpp b/include/strong_type/range.hpp
@@ -33,7 +33,7 @@ template <typename T, typename Tag, typename ... M>
 class range::modifier<
     type<T, Tag, M...>,
     impl::void_t<
-        decltype(std::declval<T>().begin() == std::declval<T>().end())
+        decltype(std::declval<T&>().begin() == std::declval<T&>().end())
     >
 >
 {
@@ -97,6 +97,7 @@ class range::modifier<
     }
 
     template <typename TT = const T&>
+    constexpr
     decltype(std::declval<TT>().size())
     size()
     const

diff --git a/test/test_range.cpp b/test/test_range.cpp
@@ -16,6 +16,7 @@
 #include "catch2.hpp"
 
 #include <forward_list>
+#include <array>
 
 namespace {
     template<typename R, typename = int>
@@ -80,4 +81,19 @@ TEST_CASE("range of sized type has size")
 
     iv v{3,2,1, 0};
     REQUIRE(v.size() == 4);
+}
+
+TEST_CASE("constexpr size")
+{
+    using ia = strong::type
+            <
+                    std::array<int, 4>,
+                    struct ia_,
+                    strong::range,
+                    strong::default_constructible
+            >;
+
+    static constexpr ia a{};
+    REQUIRE(a.size() == 4);
+    STATIC_REQUIRE(a.size() == 4);
 }