llvm/llvm-project

[Clang] Explain satisfaction failure for more type traits

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#141,911 opened on May 29, 2025

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clang:diagnosticsclang:frontendgood first issue

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Description

Last week, we added the scaffolding for clang to explain why a standard type trait is not satisfied - when used either in a static_assert or as atomic constraint, in Sema::DiagnoseTypeTraitDetails (#141238)

https://gcc.godbolt.org/z/xb7PcxzTx

So far, this has only been done for std::is_trivially_relocatable.

There are plenty of type traits that could benefit from additional diagnostics https://eel.is/c++draft/type.traits#meta.type.synop

I figure adding support for more type traits (one at a time!) could be a good first issue, and it's always nice to improve our diagnostics.

Contributor guide

Research direction
Start by examining the existing implementation for std::is trivially relocatable in Sema::DiagnoseTypeTraitDetails, then pick a type trait from the standard list and add similar diagnostics.
Tech stack
cpp
Domain
backend
Issue type
Feature
DifficultyEstimated implementation difficulty for a new contributor, from 1 for very small changes to 5 for expert-level work.
2
Estimated timeA rough time range for an experienced contributor to investigate, implement, test, and prepare a pull request.
1-3 hours
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Active
ClarityHow clearly the issue explains the expected change, acceptance criteria, and next step.
Mostly clear
Prerequisites
GitC++
Newbie friendlinessA 1-100 score estimating how approachable this issue is for first-time contributors.
75