swiftlang/swift

Separate `-dump-clang-diagnostics` into two features.

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#87757 opened on Mar 9, 2026

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 (4 comments) (0 reactions) (1 assignee)Swift (69,989 stars) (10,719 forks)batch import
clang importergood first issue

Description

Motivation

-dump-clang-diagnostics currently does two somewhat orthogonal things:

  1. emits ad-hoc "remarks" on things ClangImporter is doing to stderr
  2. emits clang diagnostics through both clang's and swift's diagnostic engine

Proposed solution

We should extract 1) into actual remarks, and enable them with -Rclang-importer (or whatever option https://github.com/swiftlang/swift/pull/87726 ends up adding).

Alternatives considered

-dump-clang-diagnostics may be left with just 2), or also enabling -Rclang-importer by default to keep the same behavior. I personally lean towards the former to avoid tangling orthogonal concepts, but I don't have a strong opinion.

Additional information

No response

Contributor guide

Tech stack
swiftcshell
Domain
backenddeveloper experiencetooling
Issue type
refactor
DifficultyEstimated implementation difficulty for a new contributor, from 1 for very small changes to 5 for expert-level work.
4
Estimated timeA rough time range for an experienced contributor to investigate, implement, test, and prepare a pull request.
3-5 days
Activity statusHow available the issue appears right now: fresh, active, stale, blocked, or waiting on maintainer input.
blocked
ClarityHow clearly the issue explains the expected change, acceptance criteria, and next step.
clear
Prerequisites
Swift compiler internalsClangImporterDiagnostics system
Newbie friendlinessA 1-100 score estimating how approachable this issue is for first-time contributors.
25
Research direction
Investigate the current implementation of ` dump clang diagnostics` in the Swift compiler (likely in `lib/ClangImporter/`). Separate the ad hoc remarks into actual remarks using ` Rclang importer` (as proposed in https://github.com/swiftlang/swift/pull/87726). Determine which part should remain under ` dump clang diagnostics` and whether to enable both by default. The issue has an assignee, so clarify with them if any work is already in progress.