Use `tracing` instead of `log`

[oli-obk]

Proposal

1. Replace all uses of the log crate with tracing (there are verbatim replacements for the logging macros, so no code changes)
2. Replace all uses of {:?} in tracing macro invocations with ?value infront of the format string
3. Introduce span! invocations to give us hirerarchical logs

Mentors or Reviewers

• @oli-obk

Process

The main points of the Major Change Process is 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.

[eddyb]

@rustbot second

cc @hawkw @davidbarsky @jackh726

[hawkw]

👋 I'd be happy to help out with this, either in the form of answering questions and giving advice, or in the form of actually sending PRs. :)

Note that because tracing has an adapter for converting log::Records into tracing Events, it's also possible to do the migration incrementally, crate-by-crate.