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Semantic check of mut restrictions - #159906

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CoCo-Japan-pan wants to merge 8 commits into
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CoCo-Japan-pan:mut-restriction-check
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Semantic check of mut restrictions#159906
CoCo-Japan-pan wants to merge 8 commits into
rust-lang:mainfrom
CoCo-Japan-pan:mut-restriction-check

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@CoCo-Japan-pan CoCo-Japan-pan commented Jul 25, 2026 •
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This PR implements semantic checks for mut restrictions proposed in RFC 3323, as part of the related GSoC project.
It lowers field restriction information from HIR into rustc_middle::ty::FieldDef and adds a MIR-level lint that rejects restricted field mutations and struct expressions. As parsing (#156824) and path resolution (#159125) have already been implemented, this PR provides a working implementation of mut restrictions.

Tracking issue: #105077
r? @Urgau
cc @jhpratt

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rustbot commented Jul 25, 2026

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Some changes occurred to MIR optimizations

cc @rust-lang/wg-mir-opt

@rustbot rustbot added S-waiting-on-review Status: Awaiting review from the assignee but also interested parties. T-compiler Relevant to the compiler team, which will review and decide on the PR/issue. T-rustdoc Relevant to the rustdoc team, which will review and decide on the PR/issue. labels Jul 25, 2026
@rustbot rustbot added the T-rustdoc-frontend Relevant to the rustdoc-frontend team, which will review and decide on the web UI/UX output. label Jul 25, 2026
@CoCo-Japan-pan CoCo-Japan-pan changed the title Mut restriction check Semantic check of mut restrictions Jul 25, 2026
Urgau
Urgau reviewed Jul 25, 2026
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@Urgau Urgau left a comment •
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Good start, mostly some tests related comments.

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Comment thread compiler/rustc_hir_analysis/src/collect.rs Outdated
Comment thread compiler/rustc_mir_transform/src/lib.rs
Comment on lines 415 to 421
// MIR-level lints.
&Lint(check_inline::CheckForceInline),
&Lint(check_call_recursion::CheckCallRecursion),
&Lint(check_packed_ref::CheckPackedRef),
&Lint(check_const_item_mutation::CheckConstItemMutation),
&Lint(check_mut_restriction::CheckMutRestriction),
&Lint(function_item_references::FunctionItemReferences),

@Urgau Urgau Jul 25, 2026

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(Not for this PR) Most of those so called "MIR lints" actually emit hard errors of an lint. We should find another name as it's quite confusing to see a "lint" emit a hard errors.

Comment thread compiler/rustc_mir_transform/src/check_mut_restriction.rs Outdated
Comment thread compiler/rustc_mir_transform/src/check_mut_restriction.rs
Comment thread compiler/rustc_mir_transform/src/check_mut_restriction.rs
Comment thread tests/ui/mut-restriction/mut-restriction-construction.rs Outdated
Comment thread tests/ui/mut-restriction/mut-restriction-check.rs
Comment thread tests/ui/mut-restriction/mut-restriction-check.rs
Comment thread tests/ui/mut-restriction/mut-restriction-check.rs
Comment thread tests/ui/mut-restriction/mut-restriction-check.rs
Comment on lines +179 to +205
fn change_fooe(foo: &mut foo::bar::FooE) {
match foo {
foo::bar::FooE::Default => {}
foo::bar::FooE::Var {
alpha, //[e2015]~ ERROR field cannot be mutated outside `foo::bar`
//[e2018]~^ ERROR field cannot be mutated outside `crate::foo::bar`
beta, //[e2015]~ ERROR field cannot be mutated outside `foo`
//[e2018]~^ ERROR field cannot be mutated outside `crate::foo`
gamma, // ok
} => {
*alpha = 1;
*beta = 1;
*gamma = 1;
}
foo::bar::FooE::Tup(
alpha, //[e2015]~ ERROR field cannot be mutated outside `foo::bar`
//[e2018]~^ ERROR field cannot be mutated outside `crate::foo::bar`
beta, //[e2015]~ ERROR field cannot be mutated outside `foo`
//[e2018]~^ ERROR field cannot be mutated outside `crate::foo`
gamma, // ok
) => {
*alpha = 1;
*beta = 1;
*gamma = 1;
}
}
}

@Urgau Urgau Jul 25, 2026

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@Nadrieril, can you think of another match related tests we should be testing regarding mut-restrictions?

@Urgau Urgau added S-waiting-on-author Status: This is awaiting some action (such as code changes or more information) from the author. and removed S-waiting-on-review Status: Awaiting review from the assignee but also interested parties. labels Jul 25, 2026
@Urgau

Urgau commented Jul 25, 2026

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cc @cjgillot for the MIR related part since you know more about it than me

@CoCo-Japan-pan

CoCo-Japan-pan commented Jul 28, 2026

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@rustbot ready
Sorry for the delay. I’ve added some tests to address the remaining comments. If everything looks good, I’ll squash the commits.

@rustbot rustbot added S-waiting-on-review Status: Awaiting review from the assignee but also interested parties. and removed S-waiting-on-author Status: This is awaiting some action (such as code changes or more information) from the author. labels Jul 28, 2026
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Urgau
Urgau reviewed Jul 29, 2026
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Comment thread tests/ui/mut-restriction/mut-restriction-check-asm.rs Outdated
Comment thread tests/ui/mut-restriction/mut-restriction-check-asm.rs Outdated
Comment thread tests/ui/mut-restriction/mut-restriction-check-asm.stderr Outdated
@CoCo-Japan-pan
CoCo-Japan-pan force-pushed the mut-restriction-check branch from f99a126 to 673a9db Compare July 29, 2026 13:46
Urgau
Urgau approved these changes Jul 29, 2026
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LGTM

As before, I will let @jhpratt do his review.

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@Urgau

Urgau commented Jul 31, 2026

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I was just thinking of something, we should probably remove the incompleteness of the feature.

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@CoCo-Japan-pan
CoCo-Japan-pan force-pushed the mut-restriction-check branch from 673a9db to 490f95c Compare August 1, 2026 08:03
@rustbot

rustbot commented Aug 1, 2026

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This PR was rebased onto a different main commit. Here's a range-diff highlighting what actually changed.

Rebasing is a normal part of keeping PRs up to date, so no action is needed—this note is just to help reviewers.

@jhpratt
jhpratt self-requested a review August 1, 2026 08:04
@jhpratt

jhpratt commented Aug 1, 2026

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I'll review this PR this weekend.

@CoCo-Japan-pan

CoCo-Japan-pan commented Aug 1, 2026

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Squashed the commits, and removed the incompleteness marker.

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@Urgau Urgau Urgau approved these changes
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