Build Catch3 as C++17

C++17 is still the widest common target, and a library built on it stays
usable from C++17 and every later standard, while C++20 would have left
out many users.

Concepts become enable_if on named traits in Detail/TypeTraits.hpp, which
also replaces std::remove_cvref_t and std::identity. std::span becomes
std::vector references, std::bit_cast becomes static_cast and memcpy,
template lambdas become helper templates, and std::erase_if, contains,
starts_with and ends_with have their C++17 forms. Random::Between no
longer uses a lambda over a constexpr local, which MSVC rejects outside
/permissive-, so the headers work under its default mode too.

Tests give up designated initializers, which MSVC refuses in C++17. CI
builds the matrix in C++17 and C++20, since the headers promise both.

1 files changed, 11 insertions, 5 deletions

diff --git a/src/Progmasoft/PropertyEngine.cpp b/src/Progmasoft/PropertyEngine.cpp
index 571a5ac3..7151dd1a 100644
--- a/src/Progmasoft/PropertyEngine.cpp
+++ b/src/Progmasoft/PropertyEngine.cpp
@@ -231,7 +231,7 @@ namespace Progmasoft::Catch3::Detail
                    std::size_t size,
                    bool describe)
             {
-                return Execute(ChoiceSource(std::span(choices), size), describe);
+                return Execute(ChoiceSource(choices, size), describe);
             }
 
             static PropertyResult
@@ -302,10 +302,16 @@ namespace Progmasoft::Catch3::Detail
                     // Only the examples checked here are dropped; another
                     // process may have stored new ones meanwhile.
                     database_.Update([&](std::vector<std::string> &stored) {
-                        std::erase_if(stored, [&](const std::string &token) {
-                            return std::find(tokens.begin(), tokens.end(), token)
-                                   != tokens.end();
-                        });
+                        const auto removed = std::remove_if(
+                            stored.begin(),
+                            stored.end(),
+                            [&](const std::string &token) {
+                                return std::find(tokens.begin(),
+                                                 tokens.end(),
+                                                 token)
+                                       != tokens.end();
+                            });
+                        stored.erase(removed, stored.end());
                     });
                 }
                 return std::nullopt;