---
title: Abstract
audience: LEWG
reply-to: Emanuel Spiridon
document: p4174r0
date: 2026-04-02
paper-type: proposal
---

**Title:** Named, composable type sets for concept constraints **Author:** Emanuel Spiridon (spiridonemanuel23@gmail.com) **Audience:** LEWG

# Abstract

This paper explores the possibility of adding a library addition to <type_traits> to assist the programmer when writing concept constraints. Concept constraints can be written by using the std::is_same_v tool, however the compile time logic is hard to understand, and at times, are error-prone at scale. An issue that modern concept constraints have is that, despite how simple it is once you implement fold expressions, they have no deduplication logic, concepts aren’t first-class types, and errors will dump every type.

**Compiler compatibility:** Clang 15+, GCC 12+, MSVC 19.3+ [Github implementation repository](https://github.com/progress-3325/tagging/tree/main)