Panic at computing function signature of closure with trait object

[nvksv]

Code

trait TT {}

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

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

Meta

rustc --version --verbose:

rustc 1.47.0 (18bf6b4f0 2020-10-07)
binary: rustc
commit-hash: 18bf6b4f01a6feaf7259ba7cdae58031af1b7b39
commit-date: 2020-10-07
host: x86_64-pc-windows-gnu
release: 1.47.0
LLVM version: 11.0

This bug also exists at Rust Playground.

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<Any>', 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::<impl rustc_query_system::query::config::QueryAccessors<rustc_middle::ty::context::TyCtxt> for rustc_middle::ty::query::queries::fn_sig>::compute
  10: rustc_query_system::dep_graph::graph::DepGraph<K>::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::<impl rustc_infer::infer::error_reporting::nice_region_error::NiceRegionError>::find_param_with_region
  14: rustc_infer::infer::error_reporting::nice_region_error::static_impl_trait::<impl rustc_infer::infer::error_reporting::nice_region_error::NiceRegionError>::try_report_static_impl_trait
  15: rustc_infer::infer::error_reporting::nice_region_error::NiceRegionError::try_report
  16: rustc_infer::infer::error_reporting::<impl rustc_infer::infer::InferCtxt>::report_region_errors
  17: rustc_infer::infer::InferCtxt::resolve_regions_and_report_errors
  18: rustc_typeck::check::regionck::<impl rustc_typeck::check::FnCtxt>::regionck_fn
  19: rustc_infer::infer::InferCtxtBuilder::enter
  20: rustc_typeck::check::typeck
  21: rustc_middle::ty::query::<impl rustc_query_system::query::config::QueryAccessors<rustc_middle::ty::context::TyCtxt> for rustc_middle::ty::query::queries::typeck>::compute
  22: rustc_query_system::dep_graph::graph::DepGraph<K>::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::<impl rustc_query_system::query::config::QueryAccessors<rustc_middle::ty::context::TyCtxt> for rustc_middle::ty::query::queries::typeck_item_bodies>::compute
  28: rustc_query_system::dep_graph::graph::DepGraph<K>::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::<impl rustc_query_system::query::config::QueryAccessors<rustc_middle::ty::context::TyCtxt> for rustc_middle::ty::query::queries::analysis>::compute
  34: rustc_query_system::dep_graph::graph::DepGraph<K>::with_task_impl
  35: rustc_data_structures::stack::ensure_sufficient_stack
  36: rustc_query_system::query::plumbing::get_query_impl
  37: rustc_interface::queries::<impl rustc_interface::interface::Compiler>::enter
  38: rustc_span::with_source_map
  39: rustc_interface::interface::create_compiler_and_run
  40: scoped_tls::ScopedKey<T>::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]

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]

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

Code

trait TT {}

impl (dyn TT + '_) {
    fn func(&self) {}
}

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

[lcnr]

We probably have to check for closures in try_report_static_impl_trait here.

[JohnTitor]

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