Closed
Description
Code
struct P {
x: i64,
}
impl P {
fn f(&self) -> &P {
self
}
}
fn main() {
let p0 = P { x: 0 };
let p1 = P { ..p0.f() };
}Meta
rustc --version --verbose:
rustc 1.58.1 (db9d1b20b 2022-01-20)
When running it with beta or nightly it reports the proper error:
error[[E0308]](https://doc.rust-lang.org/beta/error-index.html#E0308): mismatched types
[--> src/main.rs:13:20
](https://play.rust-lang.org/?version=beta&mode=debug&edition=2021#) |
13 | let p1 = P { ..p0.f() };
| ^^^^^^ expected struct `P`, found `&P`
Error output
error: internal compiler error: compiler/rustc_typeck/src/check/fn_ctxt/_impl.rs:319:25: while adjusting Expr { hir_id: HirId { owner: DefId(0:7 ~ rust_ice_spread_ref[b86a]::main), local_id: 11 }, kind: Path(Resolved(None, Path { span: src/main.rs:13:20: 13:22 (#0), res: Local(HirId { owner: DefId(0:7 ~ rust_ice_spread_ref[b86a]::main), local_id: 7 }), segments: [PathSegment { ident: p0#0, hir_id: Some(HirId { owner: DefId(0:7 ~ rust_ice_spread_ref[b86a]::main), local_id: 10 }), res: Some(Local(HirId { owner: DefId(0:7 ~ rust_ice_spread_ref[b86a]::main), local_id: 7 })), args: None, infer_args: true }] })), span: src/main.rs:13:20: 13:22 (#0) }, can't compose [Borrow(Ref('_#0r, Not)) -> &P] and [Borrow(Ref('_#2r, Not)) -> &P]
Backtrace
thread 'rustc' panicked at 'Box<dyn Any>', compiler/rustc_errors/src/lib.rs:1169:9
stack backtrace:
0: std::panicking::begin_panic::<rustc_errors::ExplicitBug>
1: std::panic::panic_any::<rustc_errors::ExplicitBug>
2: <rustc_errors::HandlerInner>::bug
3: <rustc_errors::Handler>::bug
4: rustc_middle::ty::context::tls::with_opt::<rustc_middle::util::bug::opt_span_bug_fmt<rustc_span::span_encoding::Span>::{closure#0}, ()>
5: rustc_middle::util::bug::opt_span_bug_fmt::<rustc_span::span_encoding::Span>
6: rustc_middle::util::bug::bug_fmt
7: <rustc_typeck::check::fn_ctxt::FnCtxt>::apply_adjustments
8: <rustc_typeck::check::method::confirm::ConfirmContext>::confirm
9: <rustc_typeck::check::fn_ctxt::FnCtxt>::lookup_method
10: <rustc_typeck::check::fn_ctxt::FnCtxt>::check_expr_kind
11: <rustc_typeck::check::fn_ctxt::FnCtxt>::check_expr_with_expectation_and_args
12: <rustc_typeck::check::fn_ctxt::FnCtxt>::check_expr_kind
13: <rustc_typeck::check::fn_ctxt::FnCtxt>::check_expr_with_expectation_and_args
14: <rustc_typeck::check::fn_ctxt::FnCtxt>::check_decl_initializer
15: <rustc_typeck::check::fn_ctxt::FnCtxt>::check_decl_local
16: <rustc_typeck::check::fn_ctxt::FnCtxt>::check_stmt
17: <rustc_typeck::check::fn_ctxt::FnCtxt>::check_block_with_expected
18: <rustc_typeck::check::fn_ctxt::FnCtxt>::check_expr_with_expectation_and_args
19: <rustc_typeck::check::fn_ctxt::FnCtxt>::check_return_expr
20: rustc_typeck::check::check::check_fn
21: <rustc_infer::infer::InferCtxtBuilder>::enter::<&rustc_middle::ty::context::TypeckResults, <rustc_typeck::check::inherited::InheritedBuilder>::enter<rustc_typeck::check::typeck_with_fallback<rustc_typeck::check::typeck::{closure#0}>::{closure#1}, &rustc_middle::ty::context::TypeckResults>::{closure#0}>
22: rustc_typeck::check::typeck
23: <rustc_query_system::dep_graph::graph::DepGraph<rustc_middle::dep_graph::dep_node::DepKind>>::with_task::<rustc_middle::ty::context::TyCtxt, rustc_span::def_id::LocalDefId, &rustc_middle::ty::context::TypeckResults>
24: rustc_data_structures::stack::ensure_sufficient_stack::<(&rustc_middle::ty::context::TypeckResults, rustc_query_system::dep_graph::graph::DepNodeIndex), rustc_query_system::query::plumbing::execute_job<rustc_query_impl::plumbing::QueryCtxt, rustc_span::def_id::LocalDefId, &rustc_middle::ty::context::TypeckResults>::{closure#3}>
25: rustc_query_system::query::plumbing::try_execute_query::<rustc_query_impl::plumbing::QueryCtxt, rustc_query_system::query::caches::DefaultCache<rustc_span::def_id::LocalDefId, &rustc_middle::ty::context::TypeckResults>>
26: <rustc_query_impl::Queries as rustc_middle::ty::query::QueryEngine>::typeck
27: <rustc_middle::hir::map::Map>::par_body_owners::<rustc_typeck::check::typeck_item_bodies::{closure#0}>
28: rustc_typeck::check::typeck_item_bodies
29: <rustc_query_system::dep_graph::graph::DepGraph<rustc_middle::dep_graph::dep_node::DepKind>>::with_task::<rustc_middle::ty::context::TyCtxt, (), ()>
30: rustc_query_system::query::plumbing::try_execute_query::<rustc_query_impl::plumbing::QueryCtxt, rustc_query_system::query::caches::DefaultCache<(), ()>>
31: <rustc_query_impl::Queries as rustc_middle::ty::query::QueryEngine>::typeck_item_bodies
32: <rustc_session::session::Session>::time::<(), rustc_typeck::check_crate::{closure#7}>
33: rustc_typeck::check_crate
34: rustc_interface::passes::analysis
35: <rustc_query_system::dep_graph::graph::DepGraph<rustc_middle::dep_graph::dep_node::DepKind>>::with_task::<rustc_middle::ty::context::TyCtxt, (), core::result::Result<(), rustc_errors::ErrorReported>>
36: rustc_data_structures::stack::ensure_sufficient_stack::<(core::result::Result<(), rustc_errors::ErrorReported>, rustc_query_system::dep_graph::graph::DepNodeIndex), rustc_query_system::query::plumbing::execute_job<rustc_query_impl::plumbing::QueryCtxt, (), core::result::Result<(), rustc_errors::ErrorReported>>::{closure#3}>
37: rustc_query_system::query::plumbing::try_execute_query::<rustc_query_impl::plumbing::QueryCtxt, rustc_query_system::query::caches::DefaultCache<(), core::result::Result<(), rustc_errors::ErrorReported>>>
38: <rustc_query_impl::Queries as rustc_middle::ty::query::QueryEngine>::analysis
39: <rustc_interface::passes::QueryContext>::enter::<rustc_driver::run_compiler::{closure#1}::{closure#2}::{closure#3}, core::result::Result<(), rustc_errors::ErrorReported>>
40: <rustc_interface::interface::Compiler>::enter::<rustc_driver::run_compiler::{closure#1}::{closure#2}, core::result::Result<core::option::Option<rustc_interface::queries::Linker>, rustc_errors::ErrorReported>>
41: rustc_span::with_source_map::<core::result::Result<(), rustc_errors::ErrorReported>, rustc_interface::interface::create_compiler_and_run<core::result::Result<(), rustc_errors::ErrorReported>, rustc_driver::run_compiler::{closure#1}>::{closure#1}>
42: <scoped_tls::ScopedKey<rustc_span::SessionGlobals>>::set::<rustc_interface::util::setup_callbacks_and_run_in_thread_pool_with_globals<rustc_interface::interface::run_compiler<core::result::Result<(), rustc_errors::ErrorReported>, rustc_driver::run_compiler::{closure#1}>::{closure#0}, core::result::Result<(), rustc_errors::ErrorReported>>::{closure#0}::{closure#0}, core::result::Result<(), rustc_errors::ErrorReported>>
My findings
- The error only exists when calling a method on an object. A normal function returning a `&'static P' doesn't cause this behavior and gives the correct error message.
- When saving the result in a temporary variable the error isn't triggered either. It only happens when calling the method as part of the spread.
The original code causing this bug used an ArcSwap which I tried to use like that:
pub fn resize(&self, max_size: usize) {
self.swap_config(PoolConfig {
max_size,
..self.inner.config.load()
});
}