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Allow phased initializing structs#152774

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dingxiangfei2009:partial-init
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Allow phased initializing structs#152774
dingxiangfei2009 wants to merge 1 commit intorust-lang:mainfrom
dingxiangfei2009:partial-init

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@dingxiangfei2009 dingxiangfei2009 commented Feb 17, 2026 •
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Partially undoing #54986

This PR introduces an unstable feature partial_init_nodrop_types. This work corresponds to the new action item in rust-lang/rust-project-goals#548.

Action Items

  • What should we do with non_exhaustive?

@rustbot rustbot added S-waiting-on-author Status: This is awaiting some action (such as code changes or more information) from the author. T-compiler Relevant to the compiler team, which will review and decide on the PR/issue. labels Feb 17, 2026
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dingxiangfei2009 commented Feb 17, 2026 •
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cc @BennoLossin @nxsaken FYI.

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BennoLossin
BennoLossin reviewed Feb 17, 2026
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@BennoLossin BennoLossin left a comment •
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Very cool to see that it's less than 200 lines changed!

Just two small things that I noticed. I can't speak on any of the actual modifications :)

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Comment thread tests/ui/borrowck/partial-init-locals.stderr
Comment thread compiler/rustc_feature/src/unstable.rs Outdated
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BennoLossin commented Feb 17, 2026

Regarding non-exhaustive: I think it's pretty simple, the reference already covers all of this:

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dingxiangfei2009 commented Mar 10, 2026

This PR is ready for previewing. It is pending a formal RFC and a tracking issue.

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@dingxiangfei2009 dingxiangfei2009 mentioned this pull request Mar 11, 2026
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theemathas commented Mar 11, 2026 •
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These two code snippets compile with this PR and causes a crash seemingly inside free.

#![feature(partial_init_locals)]

fn main() {
    let x: (String, String);
    x.0 = String::new();
}
#![feature(partial_init_locals)]

struct Thing(String, String);

fn main() {
    let x: Thing;
    x.0 = String::new();
}

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theemathas commented Mar 11, 2026

This code compiles with this PR and prints garbage data:

#![feature(partial_init_locals)]

fn main() {
    let x: (i32, i32);
    x.0 = 123;
    let weird = x.1;
    println!("{}", weird);
}

@ojeda ojeda mentioned this pull request Mar 11, 2026
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