Description
Proposal
When executing a typed copy where the type contains a niche, the compiler may insert a runtime check that the type's niche(s) are unoccupied. In practical terms, these runtime checks will be inserted strategically in order to minimize runtime overhead (checking that every reference is not null every time they appear on the left side of a MIR assignment statement would have ridiculous overhead).
I have been slowly working on an implementation of this at rust-lang/rust#104862, following my work on #570
Mentors or Reviewers
I do not have any in mind
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.