Description
Proposal
Add two new lints to the compiler that are run during collection (so post-monomorphization). One that reports large MIR locals (with a crate-wide attribute to configure the size at which linting starts) and one that reports large assignments (with a separate crate-wide attribute for configuring the size).
The idea of these two lints is to quickly give users the ability to start debugging async/await performance issues that can occur when large async blocks are moved around directly (instead of behind a box). While there may be better or more powerful schemes available, this solution is easy to implement and gives an immediate benefit.
Mentors or Reviewers
@pnkfelix who came up with the idea
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 mergeon either the MCP or the PR.
- Finding a "second" suffices for internal changes. If however, you are proposing a new public-facing feature, such as a
- 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.