ICE when spreading a reference returned by a method

[bikeshedder]

Code

https://play.rust-lang.org/?version=stable&mode=debug&edition=2021&gist=18b5d1e136c1560a01287bb5466b0228

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()
    });
}

See: bikeshedder/deadpool@b67b689#diff-3d3a3befe15b287611ab412182035e95cf96ecd0288176897fe353cc87b48767R472

[SNCPlay42]

Looks like #92010.

[bikeshedder]

Looks like the exact same problem. Since it is no longer existant in the beta or unstable channel I guess it was fixed by #92112 as well.