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Fix panic from cross-crate FnDef impl-path collision #2559

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Merged
mmcloughlin merged 2 commits into from
Jun 14, 2026
+31 −14
Merged

Fix panic from cross-crate FnDef impl-path collision #2559

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37022ff
Fix panic from cross-crate FnDef impl-path collision
mmcloughlin Jun 14, 2026
67f7e9a
Build FnDef impl path with push_segment
mmcloughlin Jun 14, 2026
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25 changes: 25 additions & 0 deletions source/rust_verify_test/tests/fndef_types.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -2037,3 +2037,28 @@ test_verify_one_file_with_options! {
}
} => Ok(())
}

test_verify_one_file_with_options! {
// Regression test for a panic due to fndef impl path collision across
// crates.
//
// The test defines 12 `Clone` impls in the crate root, which are enough to
// collide with the `Clone` impls for `Ghost` and `Tracked` in
// `verus_builtin` at the same disambiguator (brought in by `["vstd"]`).
Comment on lines +2045 to +2047

@mmcloughlin mmcloughlin Jun 14, 2026

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This is quite a fragile test in that it relies on a disambiguator collision with definitions in verus_builtin.

The ideal test would setup two synthetic crates to force a collision. However, I'm not sure there's an easy way to setup multi-crate tests? Most rust_verify_test tests are single file.

#[test] fndef_impl_path_includes_crate ["vstd"] => verus_code! {
use vstd::prelude::*;

struct S0; impl Clone for S0 { fn clone(&self) -> Self { S0 } }
struct S1; impl Clone for S1 { fn clone(&self) -> Self { S1 } }
struct S2; impl Clone for S2 { fn clone(&self) -> Self { S2 } }
struct S3; impl Clone for S3 { fn clone(&self) -> Self { S3 } }
struct S4; impl Clone for S4 { fn clone(&self) -> Self { S4 } }
struct S5; impl Clone for S5 { fn clone(&self) -> Self { S5 } }
struct S6; impl Clone for S6 { fn clone(&self) -> Self { S6 } }
struct S7; impl Clone for S7 { fn clone(&self) -> Self { S7 } }
struct S8; impl Clone for S8 { fn clone(&self) -> Self { S8 } }
struct S9; impl Clone for S9 { fn clone(&self) -> Self { S9 } }
struct S10; impl Clone for S10 { fn clone(&self) -> Self { S10 } }
struct S11; impl Clone for S11 { fn clone(&self) -> Self { S11 } }
} => Ok(())
}
14 changes: 4 additions & 10 deletions source/vir/src/ast_simplify.rs
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Expand Up @@ -24,7 +24,8 @@ use crate::context::GlobalCtx;
use crate::def::dummy_param_name;
use crate::def::is_dummy_param_name;
use crate::def::{
Spanned, positional_field_ident, prefix_tuple_param, prefix_tuple_variant, user_local_name,
Spanned, impl_fndef_path, positional_field_ident, prefix_tuple_param, prefix_tuple_variant,
user_local_name,
};
use crate::messages::Span;
use crate::messages::{error, internal_error};
Expand Down Expand Up @@ -1049,17 +1050,10 @@ fn add_fndef_axioms_to_function(
Arc::new(TypX::Datatype(tuple_dt, Arc::new(arg_typs), Arc::new(vec![])));
let trait_typ_args = Arc::new(vec![self_typ, args_tuple_typ]);

let mk_impl_path = |kind: ClosureKind| {
Arc::new(crate::ast::PathX {
krate: CrateId::Internal,
segments: Arc::new(vec![crate::def::impl_fndef(&function.x.name, kind)]),
})
};

let mut trait_impls_out: Vec<TraitImpl> = Vec::new();
for kind in [ClosureKind::Fn, ClosureKind::FnMut, ClosureKind::FnOnce] {
let trait_implx = crate::ast::TraitImplX {
impl_path: mk_impl_path(kind),
impl_path: impl_fndef_path(&function.x.name, kind),
typ_params: function.x.typ_params.clone(),
typ_bounds: function.x.typ_bounds.clone(),
trait_path: kind.trait_path(),
Expand All @@ -1074,7 +1068,7 @@ fn add_fndef_axioms_to_function(

let assoc_typ_implx = crate::ast::AssocTypeImplX {
name: Arc::new("Output".to_string()),
impl_path: mk_impl_path(ClosureKind::FnOnce),
impl_path: impl_fndef_path(&function.x.name, ClosureKind::FnOnce),
typ_params: function.x.typ_params.clone(),
typ_bounds: function.x.typ_bounds.clone(),
trait_path: ClosureKind::FnOnce.trait_path(),
Expand Down
6 changes: 2 additions & 4 deletions source/vir/src/def.rs
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Expand Up @@ -645,10 +645,8 @@ pub(crate) fn impl_closure(kind: ClosureKind, id: usize) -> Ident {
Arc::new(format!("{}{}{}", PREFIX_IMPL_CLOSURE, kind, id))
}

pub(crate) fn impl_fndef(fun: &Fun, kind: ClosureKind) -> Ident {
let joined =
fun.path.segments.iter().map(|s| s.as_str()).collect::<Vec<_>>().join(PATH_SEPARATOR);
Arc::new(format!("{}{}{}", PREFIX_IMPL_FNDEF, kind, joined))
pub(crate) fn impl_fndef_path(fun: &Fun, kind: ClosureKind) -> Path {
fun.path.push_segment(Arc::new(format!("{}{}", PREFIX_IMPL_FNDEF, kind)))
}

impl NameCtxt {
Expand Down