Diagnostics sometimes suggest items from `rustc_private` crates #135232

tgross35 · 2025-01-08T03:07:20Z

Code

This requires a compiler_builtins that includes a public or possibly public (i.e. feature gated) trait. The most recent v0.1.142 has this on Windows only (attempted update in #135180), I have a patched branch that makes this trait available on all platforms https://github.com/tgross35/rust/tree/experiment-builtins-math.

trait Trait { type Bar; }
type Foo = dyn Trait<F = i32, Bar = i32>;

Current output

Running rustc +stage0 foo.rs --crate-type=lib

--> foo.rs:6:22
  |
6 | type Foo = dyn Trait<F = i32, Bar = i32>;
  |                      ^ there is a similarly named associated type `H` in the trait `compiler_builtins::math::libm::support::int_traits::DInt`

Desired output

Don't suggest using compiler_builtins unless the crate is #![feature(rustc_private)]

Rationale and extra context

My investigation on Zulip https://rust-lang.zulipchat.com/#narrow/channel/182449-t-compiler.2Fhelp/topic/Why.20do.20diagnostics.20suggest.20compiler_builtins

Rust Version

Current stage0

rustc 1.84.0-beta.1 (b4297a573 2024-11-26)
binary: rustc
commit-hash: b4297a573b4eefacd62e7ea1ba071536282d3254
commit-date: 2024-11-26
host: x86_64-unknown-linux-gnu
release: 1.84.0-beta.1
LLVM version: 19.1.4

Anything else?

No response

The text was updated successfully, but these errors were encountered:

tgross35 · 2025-01-08T03:24:38Z

The context is that compiler_builtins has a lot of traits that are usually private but are public with a feature for testing. Currently everything is wrapped in a cfged macro so the traits don't even make it to AST unless the relevant config is enabled. It would be much nicer to instead just make the relevant module conditionally private/public, but since diagnostics ignore module visibility, that means they can show up in diagnostics if the crate is accessible.

I did try making that change before rust-lang/compiler-builtins#656, which had to be reverted because of the failure at #128691 (comment). Didn't look into the cause too much at that time. But in any case, the current situation isn't very robust, and finding problems only at sync time is inconvenient.

I can try to figure this out but I'm not sure where to start. @compiler-errors this seems like your territory, any suggestions?

tgross35 · 2025-01-08T03:26:53Z

Also this only seems to apply to trait-related diagnostics, e.g. calling a function from compiler_builtins doesn't suggest anything.

fn main() {
    __adddf3(1.0, 2.0);
}

tgross35 · 2025-01-08T03:49:22Z

More reliable repro that works on stable and refers to addr2line from the sysroot

trait Trait { type Bar; }
type Foo = dyn Trait<Buf = i32, Bar = i32>;

error[E0220]: associated type `Buf` not found for `Trait`
 --> src/lib.rs:2:22
  |
2 | type Foo = dyn Trait<Buf = i32, Bar = i32>;
  |                      ^^^ there is an associated type `Buf` in the trait `addr2line::LookupContinuation`

https://play.rust-lang.org/?version=stable&mode=debug&edition=2021&gist=f137a5a714aff5759deb28283947f9c6

Looks like this might be easier than expected if this is the only kind of error, maybe just a filter at

rust/compiler/rustc_hir_analysis/src/hir_ty_lowering/errors.rs

Lines 201 to 209 in 0707499

    
           if let [best_trait] = visible_traits 
        
               .iter() 
        
               .copied() 
        
               .filter(|trait_def_id| { 
        
                   tcx.associated_items(trait_def_id) 
        
                       .filter_by_name_unhygienic(suggested_name) 
        
                       .any(|item| item.kind == assoc_kind) 
        
               }) 
        
               .collect::<Vec<_>>()[..]

.

For places where we don't want stdlib-private crates to be accessible, use `.visible_crates()` rather than `.crates()`. The current effect is that items in stdlib-private crates will no longer show up in diagnostics related to trait selection. Fixes: rust-lang#135232

Exclude dependencies of `std` for diagnostics Currently crates in the sysroot can show up in diagnostic suggestions, such as in rust-lang#135232. To prevent this, introduce a query `visible_crates` that excludes crates marked `is_private_dep` and use this query in user-facing areas of code. Setting `#![feature(rustc_private)]` overrides this to just use all crates, since `rustc_private` enables use of `std`'s private dependencies. Notably, this changes `all_traits` to use `.visible_crates(())` rather than `.crates(())`. This is not strictly required and filtering could happen later as-needed; however, I cannot think of any cases where traits from private dependencies should be relevant in trait selection or diagnostics, so filtering at this earlier point seems more likely to avoid similar issues in the future. This may be reviewed per-commit. Fixes: rust-lang#135232

For places where we don't want stdlib-private crates to be accessible, use `.visible_crates()` rather than `.crates()`. The current effect is that items in stdlib-private crates will no longer show up in diagnostics related to trait selection. Fixes: rust-lang#135232

Add an alternative to `tcx.all_traits()` that only shows traits that the user might be able to use, for diagnostic purposes. With this available, make use of it for diagnostics including associated type errors which fixes [1]. Includes a few comment updates for related API. Fixes: rust-lang#135232 [1]

Exclude dependencies of `std` for diagnostics Currently crates in the sysroot can show up in diagnostic suggestions, such as in rust-lang#135232. To prevent this, duplicate `all_traits` into `visible_traits` which only shows traits in non-private crates. Setting `#![feature(rustc_private)]` overrides this and makes items in private crates visible as well, since `rustc_private` enables use of `std`'s private dependencies. This may be reviewed per-commit. Fixes: rust-lang#135232

Add an alternative to `tcx.all_traits()` that only shows traits that the user might be able to use, for diagnostic purposes. With this available, make use of it for diagnostics including associated type errors which fixes [1]. Includes a few comment updates for related API. Fixes: rust-lang#135232 [1]

Add an alternative to `tcx.all_traits()` that only shows traits that the user might be able to use, for diagnostic purposes. With this available, make use of it for diagnostics including associated type errors, which is part of the problem with [1]. Includes a few comment updates for related API. [1]: rust-lang#135232

In order to avoid diagnostics suggesting stdlib-private dependencies, make everything that is a direct dependency of any `std` crates private by default. Note that this will be overridden, if the same crate is public elsewhere in the crate graph then that overrides the private default. It may also be feasible to do this in the library crate, marking `std`'s dependencies private via Cargo. However, given that the feature is still rather unstable, doing this within the compiler seems more straightforward. Fixes: rust-lang#135232 [1]

Add an alternative to `tcx.all_traits()` that only shows traits that the user might be able to use, for diagnostic purposes. With this available, make use of it for diagnostics including associated type errors, which is part of the problem with [1]. Includes a few comment updates for related API. [1]: rust-lang#135232

In order to avoid diagnostics suggesting stdlib-private dependencies, make everything that is a direct dependency of any `std` crates private by default. Note that this will be overridden, if the same crate is public elsewhere in the crate graph then that overrides the private default. It may also be feasible to do this in the library crate, marking `std`'s dependencies private via Cargo. However, given that the feature is still rather unstable, doing this within the compiler seems more straightforward. Fixes: rust-lang#135232 [1]

Add an alternative to `tcx.all_traits()` that only shows traits that the user might be able to use, for diagnostic purposes. With this available, make use of it for diagnostics including associated type errors, which is part of the problem with [1]. Includes a few comment updates for related API. [1]: rust-lang#135232

…arrowLii Exclude dependencies of `std` for diagnostics Currently crates in the sysroot can show up in diagnostic suggestions, such as in rust-lang#135232. To prevent this, duplicate `all_traits` into `visible_traits` which only shows traits in non-private crates. Setting `#![feature(rustc_private)]` overrides this and makes items in private crates visible as well, since `rustc_private` enables use of `std`'s private dependencies. This may be reviewed per-commit. Fixes: rust-lang#135232

Exclude dependencies of `std` for diagnostics Currently crates in the sysroot can show up in diagnostic suggestions, such as in rust-lang/rust#135232. To prevent this, duplicate `all_traits` into `visible_traits` which only shows traits in non-private crates. Setting `#![feature(rustc_private)]` overrides this and makes items in private crates visible as well, since `rustc_private` enables use of `std`'s private dependencies. This may be reviewed per-commit. Fixes: rust-lang/rust#135232

tgross35 added A-diagnostics Area: Messages for errors, warnings, and lints T-compiler Relevant to the compiler team, which will review and decide on the PR/issue. labels Jan 8, 2025

jieyouxu added the D-confusing Diagnostics: Confusing error or lint that should be reworked. label Jan 8, 2025

tgross35 self-assigned this Jan 9, 2025

tgross35 mentioned this issue Jan 9, 2025

Exclude dependencies of std for diagnostics #135278

Merged

bors closed this as completed in ed63539 Jan 14, 2025

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Diagnostics sometimes suggest items from `rustc_private` crates #135232

Diagnostics sometimes suggest items from `rustc_private` crates #135232

tgross35 commented Jan 8, 2025 •

edited

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tgross35 commented Jan 8, 2025

tgross35 commented Jan 8, 2025

tgross35 commented Jan 8, 2025 •

edited

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Diagnostics sometimes suggest items from rustc_private crates #135232

Diagnostics sometimes suggest items from rustc_private crates #135232

Comments

tgross35 commented Jan 8, 2025 • edited Loading

Code

Current output

Desired output

Rationale and extra context

Rust Version

Anything else?

tgross35 commented Jan 8, 2025

tgross35 commented Jan 8, 2025

tgross35 commented Jan 8, 2025 • edited Loading

Diagnostics sometimes suggest items from `rustc_private` crates #135232

Diagnostics sometimes suggest items from `rustc_private` crates #135232

tgross35 commented Jan 8, 2025 •

edited

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tgross35 commented Jan 8, 2025 •

edited

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