lint ImproperCTypes: refactor linting architecture (part 2) by niacdoial · Pull Request #146273 · rust-lang/rust

niacdoial · 2025-09-06T15:08:57Z

This is the second PR in an effort to split #134697 (refactor plus overhaul of the ImproperCTypes family of lints) into individually-mergeable parts.

Contains the changes of the first PR, and splits the core type checking function into several bits, each focused on a specific aspect of FFI-safety.
Some logic which was outside of said core function was also moved into the new functions.

Superset of: #146271

tgross35

I think a lot of this makes sense, but aren't there behavior changes here? It looks like tuples and arrays may be treated slightly differently.

Which is probably fine, that would ideally just be split from the refactoring and come with test updates.

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niacdoial · 2025-09-06T20:33:01Z

I think a lot of this makes sense, but aren't there behavior changes here? It looks like tuples and arrays may be treated slightly differently.

Which is probably fine, that would ideally just be split from the refactoring and come with test updates.

I moved the actual change in behaviour in a later commit.
The rest of the changes here are just an exercise in moving more of the type-checking logic into the visit_* methods.

tgross35 · 2025-09-07T05:13:12Z

I moved the actual change in behaviour in a later commit.
The rest of the changes here are just an exercise in moving more of the type-checking logic into the visit_* methods.

"split type visiting into subfunctions" still has some changes right? Array went from just checking the type to checking whether or not it is in a function. Which is probably a reasonable change to make, it should just be its own thing (and come with a test update).

(Possible I'm missing something here)

niacdoial · 2025-09-07T11:27:26Z

Array went from just checking the type to checking whether or not it is in a function.

That's a bit of logic that was moved from check_type to visit_type

tgross35 · 2025-09-13T19:05:21Z

Btw if these are ready for a more final review, feel free to un-draft them (just gets them actually into my queue)

niacdoial · 2025-09-19T21:16:32Z

just double-checked:
I'm pretty sure I covered all the things you made reviews on
(the one change in this force-push is renaming IndirectionType->IndirectionKind)

tgross35 · 2025-09-22T18:35:19Z

@niacdoial what exactly are these waiting on? I assume they're close to ready based on your above comment, but they are still marked as drafts.

niacdoial · 2025-09-22T18:39:07Z

ah, I knew I was missing something (talking about the PR still being a draft)

tgross35

Sorry for the delay here, I've been behind for al little while. Should be catching up now, though

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rustbot · 2026-04-09T05:40:36Z

Reminder, once the PR becomes ready for a review, use @rustbot ready.

niacdoial · 2026-04-15T21:12:07Z

ok! all is split, with the two commits "before" this one being #155358 and #155359
sorry it took some time, I ended up being far more busy than I thought I would

petrochenkov · 2026-04-16T11:17:25Z

Blocked on #155359.
@rustbot blocked

….2, r=petrochenkov Improperctypes refactor2.2 This is "part 2/3 of 2/3 of 1/2" of the original pull request rust-lang#134697 (refactor plus overhaul of the ImproperCTypes family of lints) (all pulls of this series of pulls are supersets of the previous pulls.) previous pull: rust-lang#155358 next pull: rust-lang#146273 This commit splits the lint's `visit_type` function into multiple functions that focus on specific things: - visit_indirection (references, boxes, raw pointers) - visit_variant_fields (the list of fields of a struct, enum variant, or union) - visit_enum - visit_struct_or_union - visit_type (most "easy" decisions such as labeling `char` unsafe are here) since, during these visits, we often move from an "outer type" to an "inner type" (structs, arrays, pointers, etc...), two structs have been added to track the current state of a visit: - VisitorState tracks the state related to the "original type" being checked (function argument/return, static variable) - OuterTyData tracks the data related to the type "immediately outer to the current visited type" r? petrochenkov (because you asked me to)

Rollup merge of #155359 - niacdoial:improperctypes-refactor2.2, r=petrochenkov Improperctypes refactor2.2 This is "part 2/3 of 2/3 of 1/2" of the original pull request #134697 (refactor plus overhaul of the ImproperCTypes family of lints) (all pulls of this series of pulls are supersets of the previous pulls.) previous pull: #155358 next pull: #146273 This commit splits the lint's `visit_type` function into multiple functions that focus on specific things: - visit_indirection (references, boxes, raw pointers) - visit_variant_fields (the list of fields of a struct, enum variant, or union) - visit_enum - visit_struct_or_union - visit_type (most "easy" decisions such as labeling `char` unsafe are here) since, during these visits, we often move from an "outer type" to an "inner type" (structs, arrays, pointers, etc...), two structs have been added to track the current state of a visit: - VisitorState tracks the state related to the "original type" being checked (function argument/return, static variable) - OuterTyData tracks the data related to the type "immediately outer to the current visited type" r? petrochenkov (because you asked me to)

rustbot · 2026-04-21T21:31:01Z

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.

niacdoial · 2026-04-22T10:55:10Z

@rustbot review

Another user-transparent change, unifying outer-type information and the existing VisitorState flags.

In order to follow along with the efforts to properly distinguish already-normalised and unnormalized types, we separate the internal interfaces of this lint that rely on normalized types from those that do not. We do that by adding the `Unnormalized` wrapper to some interfaces.

niacdoial · 2026-05-02T22:27:42Z

added a new commit to better make use of the Unnormalized<> type wrapper that appeared during one of the rebases for this PR and its sub-PRs

niacdoial · 2026-05-03T08:45:22Z

wait, have I not...?
@rustbot review

petrochenkov · 2026-05-04T10:37:59Z

    #[derive(Clone, Copy, Debug, PartialEq, Eq)]
-    struct VisitorState: u8 {
+    struct RootUseFlags: u16 {


Suggested change

struct RootUseFlags: u16 {

struct RootUseFlags: u8 {

Extending to 16 bit is not (yet?) necessary.

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petrochenkov · 2026-05-04T10:41:50Z

@@ -286,8 +295,10 @@ enum IndirectionKind {
 }

 bitflags! {
+    /// VisitorState flags that are linked with the root type's use.
+    /// (These are the permanent part of the state, kept when visiting new mir::Ty.)


Suggested change

/// (These are the permanent part of the state, kept when visiting new mir::Ty.)

/// (These are the permanent part of the state, kept when visiting new `Ty`.)

I've just noticed, what is mir::Ty?
In this PR it seems to refer to the usual Ty, which is not "mir".

View changes since the review

ah, my bad.
It was to differentiate from hir::Ty (rustc_hir::ty::Ty) used elsewhere in the file, and I kinda assumed this meant the usual Ty (rustc_middle::ty::Ty) is MIR.

Should I still make it obvious this isn't the same as hir::Ty?

If you need to disambiguate, then ty::Ty or hir::Ty can be used (whatever requires less annotations).

petrochenkov · 2026-05-04T10:44:57Z

r=me after addressing the remaining nits.
@rustbot author

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lint ImproperCTypes: refactor linting architecture (part 3) #146275

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lint ImproperCTypes: overhaul (take 2 of "better handling of indirections") #134697

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Comment thread compiler/rustc_lint/src/types/improper_ctypes.rs Outdated

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Improperctypes refactor2.2 #155359

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ImproperCTypes: merge outer_ty information into VisitorState

8205b12

Another user-transparent change, unifying outer-type information and the existing VisitorState flags.

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	/// (These are the permanent part of the state, kept when visiting new mir::Ty.)
	/// (These are the permanent part of the state, kept when visiting new `Ty`.)

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