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Merged
merged 7 commits into from
Sep 17, 2025
Merged

Detect attempt to use var-args in closure #146581

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9405e76
Detect attempt to use var-args in closure
estebank Sep 15, 2025
0e290e4
Silence inference error on `PatKind::Err`
estebank Sep 15, 2025
a84c8de
Fix existing test
estebank Sep 15, 2025
c916e88
fmt
estebank Sep 16, 2025
ed85f98
remove redundant test
estebank Sep 16, 2025
8306a2f
Reword note
estebank Sep 16, 2025
e9270e3
Detect top-level `...` in argument type
estebank Sep 16, 2025
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10 changes: 8 additions & 2 deletions compiler/rustc_trait_selection/src/error_reporting/infer/need_type_info.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -4,7 +4,7 @@ use std::path::PathBuf;

use rustc_errors::codes::*;
use rustc_errors::{Diag, IntoDiagArg};
use rustc_hir as hir;
use rustc_hir::{self as hir, PatKind};
use rustc_hir::def::{CtorOf, DefKind, Namespace, Res};
use rustc_hir::def_id::{DefId, LocalDefId};
use rustc_hir::intravisit::{self, Visitor};
Expand Down Expand Up @@ -512,7 +512,7 @@ impl<'a, 'tcx> TypeErrCtxt<'a, 'tcx> {
type_name: ty_to_string(self, ty, def_id),
});
}
InferSourceKind::ClosureArg { insert_span, ty } => {
InferSourceKind::ClosureArg { insert_span, ty, .. } => {
infer_subdiags.push(SourceKindSubdiag::LetLike {
span: insert_span,
name: String::new(),
Expand Down Expand Up @@ -652,6 +652,10 @@ impl<'a, 'tcx> TypeErrCtxt<'a, 'tcx> {
}),
};
*err.long_ty_path() = long_ty_path;
if let InferSourceKind::ClosureArg { kind: PatKind::Err(_), .. } = kind {
// We will have already emitted an error about this pattern.
err.downgrade_to_delayed_bug();
Comment on lines +657 to +658
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@lcnr lcnr Sep 15, 2025 •
edited
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hmm, surprised we don't have a way to silence a lint by passing in an ErrorGuaranteed. We could then do

        if let InferSourceKind::ClosureArg { kind: PatKind::Err(guar), .. } = kind {
            err.silence_via_error_guaranteed(guar);
        }
}

though maybe even better... change this function to return Result<Diag, ErrorGuaranteed> and avoid creating a diagnostic at all edit: seems annoying to do 😅

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I guess the rationale for downgrade_to_delayed_bug itself not taking an ErrorGuarantee is because itself is kind of an error guarantee already :)

The guarantee is more critical for anything that could cause a binary to be emitted otherwise.

}
err
}
}
Expand All @@ -673,6 +677,7 @@ enum InferSourceKind<'tcx> {
ClosureArg {
insert_span: Span,
ty: Ty<'tcx>,
kind: PatKind<'tcx>,
},
GenericArg {
insert_span: Span,
Expand Down Expand Up @@ -1197,6 +1202,7 @@ impl<'a, 'tcx> Visitor<'tcx> for FindInferSourceVisitor<'a, 'tcx> {
kind: InferSourceKind::ClosureArg {
insert_span: param.pat.span.shrink_to_hi(),
ty: param_ty,
kind: param.pat.kind,
},
})
}
Expand Down
1 change: 0 additions & 1 deletion tests/ui/closures/varargs-in-closure-isnt-supported.rs
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Expand Up @@ -4,7 +4,6 @@
unsafe extern "C" fn thats_not_a_pattern(mut ap: ...) -> u32 {
let mut lol = |...| (); //~ ERROR: unexpected `...`
unsafe { ap.arg::<u32>() } //~^ NOTE: C-variadic type `...` is not allowed here
//~| ERROR: type annotations needed
//~| NOTE: not a valid pattern
}

Expand Down
14 changes: 1 addition & 13 deletions tests/ui/closures/varargs-in-closure-isnt-supported.stderr
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Expand Up @@ -6,17 +6,5 @@ LL | let mut lol = |...| ();
|
= note: C-variadic type `...` is not allowed here

error[E0282]: type annotations needed
--> $DIR/varargs-in-closure-isnt-supported.rs:5:20
|
LL | let mut lol = |...| ();
| ^^^
|
help: consider giving this closure parameter an explicit type
|
LL | let mut lol = |...: /* Type */| ();
| ++++++++++++

error: aborting due to 2 previous errors
error: aborting due to 1 previous error

For more information about this error, try `rustc --explain E0282`.
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