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Rollup merge of #122564 - Bryanskiy:delegation-fixes, r=compiler-errors
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Delegation: fix ICE on duplicated associative items

Currently, functions delegation is only supported for delegation items with early resolved paths e.g. free functions and trait methods. During name resolution, information about function signatures is collected, including the number of parameters and whether there are self arguments. This information is then used when lowering from a delegation item into a regular function(`rustc_ast_lowering/src/delegation.rs`). The signature is usually inherited from path resolution id(`path_id`). However, in the case of trait impls `path_id` and `item_id` may be different:

```rust
trait Trait {
    fn foo(&self) -> u32 { 0 }
}

struct S;

mod to_reuse {
    use crate::S;

    pub fn foo(_: &S) -> u32 { 0 }
}

impl Trait for S {
    reuse to_reuse::foo { self }
    //~^ The signature should be inherited from item id instead of resolution id
}

```

Let's now consider an example from [issue](#119920). Due to duplicated associative elements partial resolution for one of them will not be recorded:

https://github.com/rust-lang/rust/blob/9023f908cfbe7a475f369717a61cb8eb865cfd25/compiler/rustc_resolve/src/late.rs#L3153-L3162

Which leads to an incorrect `is_in_trait_impl`

https://github.com/rust-lang/rust/blob/9023f908cfbe7a475f369717a61cb8eb865cfd25/compiler/rustc_ast_lowering/src/item.rs#L981-L986

Which leads to an incorrect id for signature inheritance

https://github.com/rust-lang/rust/blob/9023f908cfbe7a475f369717a61cb8eb865cfd25/compiler/rustc_ast_lowering/src/delegation.rs#L99-L105

Which lead to an ICE from original issue.

This patch fixes wrong `is_in_trait_impl`  calculation.

fixes #119920
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fmease committed Mar 16, 2024
2 parents c2b7d77 + b2ed9d0 commit 7b7a7fc
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Showing 3 changed files with 52 additions and 8 deletions.
14 changes: 6 additions & 8 deletions compiler/rustc_ast_lowering/src/item.rs
Expand Up @@ -373,6 +373,7 @@ impl<'hir> LoweringContext<'_, 'hir> {
(trait_ref, lowered_ty)
});

self.is_in_trait_impl = trait_ref.is_some();
let new_impl_items = self
.arena
.alloc_from_iter(impl_items.iter().map(|item| self.lower_impl_item_ref(item)));
Expand Down Expand Up @@ -978,13 +979,6 @@ impl<'hir> LoweringContext<'_, 'hir> {
}

fn lower_impl_item_ref(&mut self, i: &AssocItem) -> hir::ImplItemRef {
let trait_item_def_id = self
.resolver
.get_partial_res(i.id)
.map(|r| r.expect_full_res().opt_def_id())
.unwrap_or(None);
self.is_in_trait_impl = trait_item_def_id.is_some();

hir::ImplItemRef {
id: hir::ImplItemId { owner_id: hir::OwnerId { def_id: self.local_def_id(i.id) } },
ident: self.lower_ident(i.ident),
Expand All @@ -1000,7 +994,11 @@ impl<'hir> LoweringContext<'_, 'hir> {
},
AssocItemKind::MacCall(..) => unimplemented!(),
},
trait_item_def_id,
trait_item_def_id: self
.resolver
.get_partial_res(i.id)
.map(|r| r.expect_full_res().opt_def_id())
.unwrap_or(None),
}
}

Expand Down
23 changes: 23 additions & 0 deletions tests/ui/delegation/duplicate-definition-inside-trait-impl.rs
@@ -0,0 +1,23 @@
#![feature(fn_delegation)]
//~^ WARN the feature `fn_delegation` is incomplete

trait Trait {
fn foo(&self) -> u32 { 0 }
}

struct F;
struct S;

mod to_reuse {
use crate::S;

pub fn foo(_: &S) -> u32 { 0 }
}

impl Trait for S {
reuse to_reuse::foo { self }
reuse Trait::foo;
//~^ ERROR duplicate definitions with name `foo`
}

fn main() {}
23 changes: 23 additions & 0 deletions tests/ui/delegation/duplicate-definition-inside-trait-impl.stderr
@@ -0,0 +1,23 @@
error[E0201]: duplicate definitions with name `foo`:
--> $DIR/duplicate-definition-inside-trait-impl.rs:19:5
|
LL | fn foo(&self) -> u32 { 0 }
| -------------------------- item in trait
...
LL | reuse to_reuse::foo { self }
| ---------------------------- previous definition here
LL | reuse Trait::foo;
| ^^^^^^^^^^^^^^^^^ duplicate definition

warning: the feature `fn_delegation` is incomplete and may not be safe to use and/or cause compiler crashes
--> $DIR/duplicate-definition-inside-trait-impl.rs:1:12
|
LL | #![feature(fn_delegation)]
| ^^^^^^^^^^^^^
|
= note: see issue #118212 <https://github.com/rust-lang/rust/issues/118212> for more information
= note: `#[warn(incomplete_features)]` on by default

error: aborting due to 1 previous error; 1 warning emitted

For more information about this error, try `rustc --explain E0201`.

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