[source_location] implement context tracking

Author: Tsche

include/rsl/source_location

@@ -1,31 +1,74 @@
-#pragma once
+#include <cstddef>
+#include <meta>
 #include <source_location>
 #include <string_view>
-#include <meta>
-#include <cstddef>
-
-#include <rsl/string_view>
 
 namespace rsl {
-struct source_location {
-  rsl::string_view file;
-  rsl::string_view function;
-  std::size_t line;
-  std::size_t column;
-
-  consteval source_location(std::source_location sloc = std::source_location::current())
-      : file(std::define_static_string(sloc.file_name()))
-      , function(std::define_static_string(sloc.function_name()))
-      , line(sloc.line())
-      , column(sloc.column()) {}
-
-  explicit source_location(rsl::string_view file,
-                           rsl::string_view function,
-                           std::size_t line,
-                           std::size_t column = 0)
-      : file(file)
-      , function(function)
-      , line(line)
-      , column(column) {}
+
+class source_location {
+  struct RawSloc {
+    const char* file_name     = std::define_static_string("");
+    const char* function_name = std::define_static_string("");
+    unsigned line             = 0;
+    unsigned column           = 0;
+  };
+
+  struct SourceContext : RawSloc {
+    consteval SourceContext(RawSloc raw) : RawSloc(raw) {}
+
+    constexpr virtual ~SourceContext()                                 = default;
+    consteval virtual std::meta::info scope() const                    = 0;
+    consteval virtual std::meta::access_context access_context() const = 0;
+  };
+
+  template <std::meta::access_context R, RawSloc Data>
+  consteval static SourceContext const* make_context() {
+    struct SourceContextImpl : SourceContext {
+      using SourceContext::SourceContext;
+      consteval virtual std::meta::info scope() const { return R.scope(); }
+      consteval virtual std::meta::access_context access_context() const { return R; }
+    };
+    constexpr static SourceContextImpl obj{Data};
+    return &obj;
+  };
+
+  // TODO: remove
+  //? this is a workaround for clang-p2996:
+  //? static member functions aren't extracted  as free functions
+  template <std::meta::access_context R, RawSloc Data>
+  constexpr static SourceContext const* _impl_context = make_context<R, Data>();
+
+  explicit consteval source_location(SourceContext const* data) : _impl_sloc(data) {}
+
+public:
+  SourceContext const* _impl_sloc = nullptr;
+  consteval source_location()
+      : _impl_sloc(make_context<std::meta::access_context::unchecked(), {}>()) {}
+
+  consteval static source_location current(
+      std::source_location sloc     = std::source_location::current(),
+      std::meta::access_context ctx = std::meta::access_context::current()) {
+    auto base = RawSloc{define_static_string(std::string_view(sloc.file_name())),
+                        define_static_string(std::string_view(sloc.function_name())),
+                        sloc.line(),
+                        sloc.column()};
+
+    // TODO: with gcc we can use make_context directly - _impl_context is a workaround for clang
+    return source_location{extract<SourceContext const*>(
+        substitute(^^_impl_context, {reflect_constant(ctx), std::meta::reflect_constant(base)}))};
+  }
+
+  // TODO wrap file_name and function_name in rsl::cstring_view as soon as implemented
+  constexpr char const* file_name() const noexcept { return _impl_sloc->file_name; }
+  constexpr char const* function_name() const noexcept { return _impl_sloc->function_name; }
+  constexpr unsigned line() const noexcept { return _impl_sloc->line; }
+  constexpr unsigned column() const noexcept { return _impl_sloc->column; }
+
+  // consteval-only extensions
+  consteval std::meta::info scope() const noexcept { return _impl_sloc->scope(); }
+  consteval std::meta::access_context access_context() const noexcept {
+    return _impl_sloc->access_context();
+  }
 };
+
 }  // namespace rsl