Panic at computing function signature of closure with trait object

nvksv commented 4 years ago

Code

trait TT {}

impl dyn TT {
    fn func(&self) {}
}

fn main() {
    let f = |x: &dyn TT| x.func();
}

Error output

error: internal compiler error: src\librustc_typeck\collect.rs:1587:13: to get the signature of a closure, use `substs.as_closure().sig()` not `fn_sig()`

thread 'rustc' panicked at 'Box<Any>', src\librustc_errors\lib.rs:918:9
note: run with `RUST_BACKTRACE=1` environment variable to display a backtrace

note: the compiler unexpectedly panicked. this is a bug.

note: we would appreciate a bug report: https://github.com/rust-lang/rust/issues/new?labels=C-bug%2C+I-ICE%2C+T-compiler&template=ice.md

note: rustc 1.47.0 (18bf6b4f0 2020-10-07) running on x86_64-pc-windows-gnu

error: aborting due to previous error

Backtrace

``` error: internal compiler error: src\librustc_typeck\collect.rs:1587:13: to get the signature of a closure, use `substs.as_closure().sig()` not `fn_sig()` thread 'rustc' panicked at 'Box', src\librustc_errors\lib.rs:918:9 stack backtrace: 0: std::panicking::begin_panic 1: rustc_errors::HandlerInner::bug 2: rustc_errors::Handler::bug 3: rustc_middle::util::bug::opt_span_bug_fmt::{{closure}} 4: rustc_middle::ty::context::tls::with_opt::{{closure}} 5: rustc_middle::ty::context::tls::with_opt 6: rustc_middle::util::bug::opt_span_bug_fmt 7: rustc_middle::util::bug::bug_fmt 8: rustc_typeck::collect::fn_sig 9: rustc_middle::ty::query:: for rustc_middle::ty::query::queries::fn_sig>::compute 10: rustc_query_system::dep_graph::graph::DepGraph::with_task_impl 11: rustc_data_structures::stack::ensure_sufficient_stack 12: rustc_query_system::query::plumbing::get_query_impl 13: rustc_infer::infer::error_reporting::nice_region_error::util::::find_param_with_region 14: rustc_infer::infer::error_reporting::nice_region_error::static_impl_trait::::try_report_static_impl_trait 15: rustc_infer::infer::error_reporting::nice_region_error::NiceRegionError::try_report 16: rustc_infer::infer::error_reporting::::report_region_errors 17: rustc_infer::infer::InferCtxt::resolve_regions_and_report_errors 18: rustc_typeck::check::regionck::::regionck_fn 19: rustc_infer::infer::InferCtxtBuilder::enter 20: rustc_typeck::check::typeck 21: rustc_middle::ty::query:: for rustc_middle::ty::query::queries::typeck>::compute 22: rustc_query_system::dep_graph::graph::DepGraph::with_task_impl 23: rustc_data_structures::stack::ensure_sufficient_stack 24: rustc_query_system::query::plumbing::get_query_impl 25: rustc_query_system::query::plumbing::ensure_query_impl 26: rustc_typeck::check::typeck_item_bodies 27: rustc_middle::ty::query:: for rustc_middle::ty::query::queries::typeck_item_bodies>::compute 28: rustc_query_system::dep_graph::graph::DepGraph::with_task_impl 29: rustc_data_structures::stack::ensure_sufficient_stack 30: rustc_query_system::query::plumbing::get_query_impl 31: rustc_typeck::check_crate 32: rustc_interface::passes::analysis 33: rustc_middle::ty::query:: for rustc_middle::ty::query::queries::analysis>::compute 34: rustc_query_system::dep_graph::graph::DepGraph::with_task_impl 35: rustc_data_structures::stack::ensure_sufficient_stack 36: rustc_query_system::query::plumbing::get_query_impl 37: rustc_interface::queries::::enter 38: rustc_span::with_source_map 39: rustc_interface::interface::create_compiler_and_run 40: scoped_tls::ScopedKey::set note: Some details are omitted, run with `RUST_BACKTRACE=full` for a verbose backtrace. note: the compiler unexpectedly panicked. this is a bug. note: we would appreciate a bug report: https://github.com/rust-lang/rust/issues/new?labels=C-bug%2C+I-ICE%2C+T-compiler&template=ice.md note: rustc 1.47.0 (18bf6b4f0 2020-10-07) running on x86_64-pc-windows-gnu query stack during panic: #0 [fn_sig] computing function signature of `main::{{closure}}#0` #1 [typeck] type-checking `main` #2 [typeck_item_bodies] type-checking all item bodies #3 [analysis] running analysis passes on this crate end of query stack error: aborting due to previous error ```

SNCPlay42 commented 4 years ago

Output on 1.46:

error[E0308]: mismatched types
 --> <source>:8:28
  |
8 |     let f = |x: &dyn TT| x.func();
  |                            ^^^^ lifetime mismatch
  |
  = note: expected reference `&(dyn TT + 'static)`
             found reference `&dyn TT`
note: the anonymous lifetime #1 defined on the body at 8:13...
 --> <source>:8:13
  |
8 |     let f = |x: &dyn TT| x.func();
  |             ^^^^^^^^^^^^^^^^^^^^^
  = note: ...does not necessarily outlive the static lifetime

error: aborting due to previous error

Changing the closure argument type to &(dyn TT + 'static) compiles successfully on both verions.

@rustbot modify labels: +A-diagnostics +A-lifetimes +regression-from-stable-to-stable

nvksv commented 4 years ago

With impl (dyn TT + '_) {...} instead of impl dyn TT {...} it compiles successfully too.

Code

```rust trait TT {} impl (dyn TT + '_) { fn func(&self) {} } fn main() { let _f = |x: &dyn TT| x.func(); } ```

lcnr commented 4 years ago

We probably have to check for closures in try_report_static_impl_trait here.

JohnTitor commented 4 years ago

Assigning P-medium as discussed as part of the Prioritization Working Group procedure and removing I-prioritize.

rust-lang / rust

Panic at computing function signature of closure with trait object #78262

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