swiftlang/swift

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

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#87,757 opened on Mar 9, 2026

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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

Research direction
Study the implementation of dump clang diagnostics in the Swift compiler, particularly in ClangImporter, to understand how it currently emits remarks and clang diagnostics. Look at PR #87726 for context on the Rclang importer option. Then propose a patch to separate the two functionalities by converting the ad hoc remarks into proper remarks triggered by Rclang importer.
Tech stack
swift
Domain
tooling
Issue type
Feature
DifficultyEstimated implementation difficulty for a new contributor, from 1 for very small changes to 5 for expert-level work.
3
Estimated timeA rough time range for an experienced contributor to investigate, implement, test, and prepare a pull request.
1-2 days
Activity statusHow available the issue appears right now: fresh, active, stale, blocked, or waiting on maintainer input.
Active
ClarityHow clearly the issue explains the expected change, acceptance criteria, and next step.
Clear
Prerequisites
Git
Newbie friendlinessA 1-100 score estimating how approachable this issue is for first-time contributors.
50