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Rust: Improve handling of Self type parameter #20707

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Merged
hvitved merged 3 commits into from
Oct 29, 2025
Merged

Rust: Improve handling of Self type parameter #20707

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9ff3c61
Rust: Add type inference tests involving `Self`
paldepind Oct 29, 2025
9022f99
Rust: Improve handling of occurrences of the `Self` type parameter
paldepind Oct 29, 2025
ce8cffc
Rust: Address comments
paldepind Oct 29, 2025
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12 changes: 6 additions & 6 deletions rust/ql/test/library-tests/type-inference/CONSISTENCY/PathResolutionConsistency.expected
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Original file line number Diff line number Diff line change
Expand Up @@ -5,9 +5,9 @@ multipleCallTargets
| dereference.rs:184:17:184:30 | ... .foo() |
| dereference.rs:186:17:186:25 | S.bar(...) |
| dereference.rs:187:17:187:29 | S.bar(...) |
| main.rs:2437:13:2437:31 | ...::from(...) |
| main.rs:2438:13:2438:31 | ...::from(...) |
| main.rs:2439:13:2439:31 | ...::from(...) |
| main.rs:2445:13:2445:31 | ...::from(...) |
| main.rs:2446:13:2446:31 | ...::from(...) |
| main.rs:2447:13:2447:31 | ...::from(...) |
| main.rs:2482:13:2482:31 | ...::from(...) |
| main.rs:2483:13:2483:31 | ...::from(...) |
| main.rs:2484:13:2484:31 | ...::from(...) |
| main.rs:2490:13:2490:31 | ...::from(...) |
| main.rs:2491:13:2491:31 | ...::from(...) |
| main.rs:2492:13:2492:31 | ...::from(...) |
46 changes: 46 additions & 0 deletions rust/ql/test/library-tests/type-inference/main.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -652,6 +652,51 @@ mod type_parameter_bounds {
}
}

mod trait_default_self_type_parameter {
// A trait with a type parameter that defaults to `Self`.
// trait TraitWithSelfTp<A = Self> {
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@hvitved hvitved Oct 29, 2025

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Remove

trait TraitWithSelfTp<A = Option<Self>> {
// TraitWithSelfTp::get_a
fn get_a(&self) -> A;
}

fn get_a<A, T: TraitWithSelfTp<A>>(thing: &T) -> A {
thing.get_a() // $ target=TraitWithSelfTp::get_a
}

// The trait bound on `T` uses the default for `A` which contains `Self`
fn tp_uses_default<S: TraitWithSelfTp>(thing: S) -> i64 {
let _ms = thing.get_a(); // $ target=TraitWithSelfTp::get_a MISSING: type=_ms:T.S
0
}

// The supertrait uses the default for `A` which contains `Self`
trait SubTraitOfTraitWithSelfTp: TraitWithSelfTp + Sized {}

fn get_a_through_tp<S: SubTraitOfTraitWithSelfTp>(thing: &S) {
// `thing` is a `TraitWithSelfTp` through the trait hierarchy
let _ms = get_a(thing); // $ target=get_a MISSING: type=_ms:T.S
}

struct MyStruct {
value: i32,
}

// The implementing trait uses the default for `A` which contains `Self`
impl TraitWithSelfTp for MyStruct {
fn get_a(&self) -> Option<Self> {
Some(MyStruct { value: self.value }) // $ fieldof=MyStruct
}
}

impl SubTraitOfTraitWithSelfTp for MyStruct {}

pub fn test() {
let s = MyStruct { value: 0 };
let _ms = get_a(&s); // $ target=get_a MISSING: type=_ms:T.MyStruct
}
}

mod function_trait_bounds {
#[derive(Debug, Clone, Copy)]
struct MyThing<T> {
Expand Down Expand Up @@ -2753,6 +2798,7 @@ fn main() {
method_impl::g(method_impl::Foo {}, method_impl::Foo {}); // $ target=g
method_non_parametric_impl::f(); // $ target=f
method_non_parametric_trait_impl::f(); // $ target=f
trait_default_self_type_parameter::test(); // $ target=test
function_trait_bounds::f(); // $ target=f
associated_type_in_trait::f(); // $ target=f
generic_enum::f(); // $ target=f
Expand Down
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