`-Dwarnings` to cover all warnings

[ojeda]

Proposal

Currently, -Dwarnings does not cover all warnings (e.g. target json file contains unused fields is not treated as an error). If it is intended that -Dwarnings covers all warnings, then this should be fixed (otherwise, it would be nice to have an alternative way to make them errors as needed). However, as @jyn514 pointed out, this would imply existing projects may require changes; thus a MCP was requested.

(Followup from rust-lang/rust#91262).

Mentors or Reviewers

Someone from "Diagnostics"?

Process

The main points of the Major Change Process are as follows:

• File an issue describing the proposal.
• A compiler team member or contributor who is knowledgeable in the area can second by writing @rustbot second.
  • Finding a "second" suffices for internal changes. If however, you are proposing a new public-facing feature, such as a -C flag, then full team check-off is required.
  • Compiler team members can initiate a check-off via @rfcbot fcp merge on either the MCP or the PR.
• Once an MCP is seconded, the Final Comment Period begins. If no objections are raised after 10 days, the MCP is considered approved.

You can read more about Major Change Proposals on forge.

Comments

This issue is not meant to be used for technical discussion. There is a Zulip stream for that. Use this issue to leave procedural comments, such as volunteering to review, indicating that you second the proposal (or third, etc), or raising a concern that you would like to be addressed.

[rustbot]

This issue is not meant to be used for technical discussion. There is a Zulip stream for that. Use this issue to leave procedural comments, such as volunteering to review, indicating that you second the proposal (or third, etc), or raising a concern that you would like to be addressed.

cc @rust-lang/compiler @rust-lang/compiler-contributors

[apiraino]

MCP candidate for closing next week (reason: lack of seconding from a member of T-compiler). See MCP process.

[ojeda]

For reference: rust-lang/rust#91262 (comment).

[jyn514]

My understanding of the current consensus with @nagisa is that this is fine for most warnings, but there are some warnings for unstable features that are explicitly warnings to avoid breaking people, which would change with this flag. To avoid a maintenance burden, @nagisa is going to change those unstable features to give hard errors instead of warnings instead.

@rustbot second

[apiraino]

@rustbot label -final-comment-period +major-change-accepted