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Fix false positive of "multiple different versions of crate X in the dependency graph" #149001

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Fix false positive of "multiple different versions of crate X in the dependency graph" #149001

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36 changes: 23 additions & 13 deletions compiler/rustc_trait_selection/src/error_reporting/traits/mod.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -22,7 +22,8 @@ use rustc_infer::traits::{
};
use rustc_middle::ty::print::{PrintTraitRefExt as _, with_no_trimmed_paths};
use rustc_middle::ty::{self, Ty, TyCtxt, TypeVisitableExt as _};
use rustc_span::{DesugaringKind, ErrorGuaranteed, ExpnKind, Span, Symbol};
use rustc_session::cstore::{ExternCrate, ExternCrateSource};
use rustc_span::{DesugaringKind, ErrorGuaranteed, ExpnKind, Span, sym};
use tracing::{info, instrument};

pub use self::overflow::*;
Expand Down Expand Up @@ -353,14 +354,26 @@ impl<'a, 'tcx> TypeErrCtxt<'a, 'tcx> {
}
}

fn get_extern_crate_renamed_symbol(&self, trait_def_id: DefId) -> Option<Symbol> {
if !trait_def_id.is_local()
&& let Some(data) = self.tcx.extern_crate(trait_def_id.krate)
&& let rustc_session::cstore::ExternCrateSource::Extern(def_id) = data.src
{
self.tcx.opt_item_name(def_id)
} else {
None
fn extern_crates_with_the_same_name(
&self,
expected_def_id: DefId,
trait_def_id: DefId,
) -> bool {
if expected_def_id.is_local() || trait_def_id.is_local() {
return false;
}
match (
self.tcx.extern_crate(expected_def_id.krate),
self.tcx.extern_crate(trait_def_id.krate),
) {
(
Some(ExternCrate { src: ExternCrateSource::Extern(expected_def_id), .. }),
Some(ExternCrate { src: ExternCrateSource::Extern(trait_def_id), .. }),
) => {
let expected_sym = self.tcx.item_name(expected_def_id);
expected_sym == self.tcx.item_name(trait_def_id) && expected_sym != sym::std
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@lcnr lcnr Nov 17, 2025

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why the check for != std?

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@rperier rperier Nov 17, 2025 •
edited
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That's weird, it seems that, in some cases, there are tests in ui suite that report two crates being imported as std. In such a case, the predicate returns true. It's the test tests/ui/typeck/issue-50687-ice-on-borrow.rs, if I remember correctly. Note: I had the same kind of reports with the old version.

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@lcnr lcnr Nov 17, 2025

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that seems worth debugging because right now it feels arbitrary.

In such cases we should figure out why things work the way they do as

  • it prevents confusing future readers by adding a comment#
  • the "arbitrary" check may actually hide a more general underlying issue and without properly fixing it

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@rperier rperier Nov 18, 2025

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Well, no my bad, it's the tests tests/ui/suggestions/issue-105645.rs and tests/ui/suggestions/mut-borrow-needed-by-trait.rs both report : "there are multiple different versions of crate std in the dependency graph" :=D .

Yeah, I agree, I am going to investigate.

}
_ => false,
}
}

Expand All @@ -377,13 +390,10 @@ impl<'a, 'tcx> TypeErrCtxt<'a, 'tcx> {
{
let krate = self.tcx.crate_name(expected_did.krate);
let name = self.tcx.item_name(expected_did);
let locally_renamed_krate = self
.get_extern_crate_renamed_symbol(expected_did)
.map_or(None, |s| if s != krate { Some(s) } else { None });
let definitions_with_same_path: UnordSet<_> = found_dids
.filter(|def_id| {
def_id.krate != expected_did.krate
&& (locally_renamed_krate == self.get_extern_crate_renamed_symbol(*def_id)
&& (self.extern_crates_with_the_same_name(expected_did, *def_id)
|| self.tcx.crate_name(def_id.krate) == krate)
&& self.tcx.item_name(def_id) == name
})
Expand Down
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