ICE: 'assertion failed: num_missing_args > 0', compiler/rustc_typeck/src/structured_errors/wrong_number_of_generic_args.rs:234:17

[memoryruins]

Code

Experimenting with #83701, the following compiles without an issue:

#![feature(explicit_generic_args_with_impl_trait)]

fn f<T: ?Sized>(_: impl AsRef<T>) {}
fn g<T: ?Sized, U: ?Sized>(_: impl AsRef<T>, _: impl AsRef<U>) {}

fn main() {
    f::<[u8]>("a");
    f::<[u8]>(b"a");
    g::<[u8], [u8]>("a", b"a");
}

But with multiple APIT using the same type parameter, ICEs occur:

#![feature(explicit_generic_args_with_impl_trait)]

fn f<T: ?Sized>(_: impl AsRef<T>, _: impl AsRef<T>) {}

fn main() {
    f::<[u8]>("a", b"a");
}

playground

rustc --version:

rustc 1.56.0-nightly (e3b1c12be 2021-08-02)

Error output

The two separate panic messages:

thread 'rustc' panicked at 'assertion failed: num_missing_args > 0', compiler/rustc_typeck/src/structured_errors/wrong_number_of_generic_args.rs:234:17

thread 'rustc' panicked at 'no warnings or errors encountered even though `delayed_good_path_bugs` issued', 

Backtrace

   Compiling playground v0.0.1 (/playground)
thread 'rustc' panicked at 'assertion failed: num_missing_args > 0', compiler/rustc_typeck/src/structured_errors/wrong_number_of_generic_args.rs:234:17
note: run with `RUST_BACKTRACE=1` environment variable to display a backtrace

error: internal compiler error: unexpected panic

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 1.56.0-nightly (e3b1c12be 2021-08-02) running on x86_64-unknown-linux-gnu

note: compiler flags: -C embed-bitcode=no -C codegen-units=1 -C debuginfo=2 --crate-type bin

note: some of the compiler flags provided by cargo are hidden

query stack during panic:
#0 [typeck] type-checking `main`
#1 [typeck_item_bodies] type-checking all item bodies
end of query stack
error: internal compiler error: trimmed_def_paths constructed
  |
  = note: delayed at    0: rustc_errors::Handler::delay_good_path_bug
             1: rustc_middle::ty::print::pretty::trimmed_def_paths
             2: rustc_data_structures::stack::ensure_sufficient_stack
             3: rustc_query_system::query::plumbing::get_query_impl
             4: rustc_query_system::query::plumbing::get_query
             5: <rustc_middle::ty::print::pretty::FmtPrinter<F> as rustc_middle::ty::print::Printer>::print_def_path
             6: rustc_middle::ty::print::pretty::<impl rustc_middle::ty::context::TyCtxt>::def_path_str_with_substs
             7: rustc_middle::ty::print::pretty::<impl rustc_middle::ty::context::TyCtxt>::def_path_str
             8: <rustc_typeck::structured_errors::wrong_number_of_generic_args::WrongNumberOfGenericArgs as rustc_typeck::structured_errors::StructuredDiagnostic>::diagnostic_common
             9: rustc_typeck::structured_errors::StructuredDiagnostic::diagnostic
            10: rustc_typeck::astconv::generics::<impl dyn rustc_typeck::astconv::AstConv>::check_generic_arg_count
            11: rustc_typeck::astconv::generics::<impl dyn rustc_typeck::astconv::AstConv>::check_generic_arg_count_for_call
            12: rustc_typeck::check::fn_ctxt::_impl::<impl rustc_typeck::check::fn_ctxt::FnCtxt>::instantiate_value_path
            13: rustc_typeck::check::expr::<impl rustc_typeck::check::fn_ctxt::FnCtxt>::check_expr_kind
            14: rustc_typeck::check::expr::<impl rustc_typeck::check::fn_ctxt::FnCtxt>::check_expr_with_expectation
            15: rustc_typeck::check::callee::<impl rustc_typeck::check::fn_ctxt::FnCtxt>::check_call
            16: rustc_typeck::check::expr::<impl rustc_typeck::check::fn_ctxt::FnCtxt>::check_expr_kind
            17: rustc_typeck::check::expr::<impl rustc_typeck::check::fn_ctxt::FnCtxt>::check_expr_with_expectation
            18: rustc_typeck::check::fn_ctxt::checks::<impl rustc_typeck::check::fn_ctxt::FnCtxt>::check_stmt
            19: rustc_typeck::check::fn_ctxt::checks::<impl rustc_typeck::check::fn_ctxt::FnCtxt>::check_block_with_expected
            20: rustc_typeck::check::expr::<impl rustc_typeck::check::fn_ctxt::FnCtxt>::check_expr_with_expectation
            21: rustc_typeck::check::expr::<impl rustc_typeck::check::fn_ctxt::FnCtxt>::check_return_expr
            22: rustc_typeck::check::check::check_fn
            23: rustc_infer::infer::InferCtxtBuilder::enter
            24: rustc_typeck::check::typeck
            25: rustc_query_system::query::plumbing::get_query_impl
            26: <rustc_query_impl::Queries as rustc_middle::ty::query::QueryEngine>::typeck
            27: rustc_middle::ty::<impl rustc_middle::ty::context::TyCtxt>::par_body_owners
            28: rustc_typeck::check::typeck_item_bodies
            29: rustc_query_system::query::plumbing::get_query_impl
            30: <rustc_query_impl::Queries as rustc_middle::ty::query::QueryEngine>::typeck_item_bodies
            31: rustc_session::utils::<impl rustc_session::session::Session>::time
            32: rustc_typeck::check_crate
            33: rustc_interface::passes::analysis
            34: rustc_query_system::query::plumbing::get_query_impl
            35: <rustc_query_impl::Queries as rustc_middle::ty::query::QueryEngine>::analysis
            36: rustc_interface::queries::<impl rustc_interface::interface::Compiler>::enter
            37: rustc_span::with_source_map
            38: rustc_interface::interface::create_compiler_and_run
            39: scoped_tls::ScopedKey<T>::set
            40: std::sys_common::backtrace::__rust_begin_short_backtrace
            41: core::ops::function::FnOnce::call_once{{vtable.shim}}
            42: <alloc::boxed::Box<F,A> as core::ops::function::FnOnce<Args>>::call_once
                       at /rustc/e3b1c12becebd21d88ca9f4364d7db8d1d380c18/library/alloc/src/boxed.rs:1572:9
            43: <alloc::boxed::Box<F,A> as core::ops::function::FnOnce<Args>>::call_once
                       at /rustc/e3b1c12becebd21d88ca9f4364d7db8d1d380c18/library/alloc/src/boxed.rs:1572:9
            44: std::sys::unix::thread::Thread::new::thread_start
                       at /rustc/e3b1c12becebd21d88ca9f4364d7db8d1d380c18/library/std/src/sys/unix/thread.rs:91:17
            45: start_thread
            46: clone
          

thread 'rustc' panicked at 'no warnings or errors encountered even though `delayed_good_path_bugs` issued', compiler/rustc_errors/src/lib.rs:1050:13
stack backtrace:
   0:     0x7fea31f246e0 - std::backtrace_rs::backtrace::libunwind::trace::h820df6e5a36600f2
                               at /rustc/e3b1c12becebd21d88ca9f4364d7db8d1d380c18/library/std/src/../../backtrace/src/backtrace/libunwind.rs:90:5
   1:     0x7fea31f246e0 - std::backtrace_rs::backtrace::trace_unsynchronized::h08422e102b839b36
                               at /rustc/e3b1c12becebd21d88ca9f4364d7db8d1d380c18/library/std/src/../../backtrace/src/backtrace/mod.rs:66:5
   2:     0x7fea31f246e0 - std::sys_common::backtrace::_print_fmt::h57fa141da5c1d78f
                               at /rustc/e3b1c12becebd21d88ca9f4364d7db8d1d380c18/library/std/src/sys_common/backtrace.rs:67:5
   3:     0x7fea31f246e0 - <std::sys_common::backtrace::_print::DisplayBacktrace as core::fmt::Display>::fmt::he771973a791a4e00
                               at /rustc/e3b1c12becebd21d88ca9f4364d7db8d1d380c18/library/std/src/sys_common/backtrace.rs:46:22
   4:     0x7fea31f927bc - core::fmt::write::h9a6d9c74526a6c1b
                               at /rustc/e3b1c12becebd21d88ca9f4364d7db8d1d380c18/library/core/src/fmt/mod.rs:1117:17
   5:     0x7fea31f15f25 - std::io::Write::write_fmt::h9d3df603db3c3ca4
                               at /rustc/e3b1c12becebd21d88ca9f4364d7db8d1d380c18/library/std/src/io/mod.rs:1667:15
   6:     0x7fea31f27d2b - std::sys_common::backtrace::_print::ha158db1ea88125c4
                               at /rustc/e3b1c12becebd21d88ca9f4364d7db8d1d380c18/library/std/src/sys_common/backtrace.rs:49:5
   7:     0x7fea31f27d2b - std::sys_common::backtrace::print::h342dde07e263fe00
                               at /rustc/e3b1c12becebd21d88ca9f4364d7db8d1d380c18/library/std/src/sys_common/backtrace.rs:36:9
   8:     0x7fea31f27d2b - std::panicking::default_hook::{{closure}}::h642e95a669718f6e
                               at /rustc/e3b1c12becebd21d88ca9f4364d7db8d1d380c18/library/std/src/panicking.rs:208:50
   9:     0x7fea31f278a0 - std::panicking::default_hook::hc5055134d92c4284
                               at /rustc/e3b1c12becebd21d88ca9f4364d7db8d1d380c18/library/std/src/panicking.rs:225:9
  10:     0x7fea32705d41 - rustc_driver::DEFAULT_HOOK::{{closure}}::{{closure}}::haff05a7eace0faae
  11:     0x7fea31f28559 - std::panicking::rust_panic_with_hook::h6f45f3f96085621d
                               at /rustc/e3b1c12becebd21d88ca9f4364d7db8d1d380c18/library/std/src/panicking.rs:627:17
  12:     0x7fea31f28017 - std::panicking::begin_panic_handler::{{closure}}::h8cc693a35602cb15
                               at /rustc/e3b1c12becebd21d88ca9f4364d7db8d1d380c18/library/std/src/panicking.rs:520:13
  13:     0x7fea31f24bcc - std::sys_common::backtrace::__rust_end_short_backtrace::h89bf48eb2468d1e3
                               at /rustc/e3b1c12becebd21d88ca9f4364d7db8d1d380c18/library/std/src/sys_common/backtrace.rs:141:18
  14:     0x7fea31f27f79 - rust_begin_unwind
                               at /rustc/e3b1c12becebd21d88ca9f4364d7db8d1d380c18/library/std/src/panicking.rs:516:5
  15:     0x7fea31ef15cb - std::panicking::begin_panic_fmt::h7b704e109b8f89ba
                               at /rustc/e3b1c12becebd21d88ca9f4364d7db8d1d380c18/library/std/src/panicking.rs:458:5
  16:     0x7fea34b51a59 - rustc_errors::HandlerInner::flush_delayed::h1214dd69c94464a0
  17:     0x7fea34b50531 - <rustc_errors::HandlerInner as core::ops::drop::Drop>::drop::h99b093f7064b7696
  18:     0x7fea34207a96 - core::ptr::drop_in_place<rustc_session::parse::ParseSess>::hf782bb3707a77e2d
  19:     0x7fea3420980e - <alloc::rc::Rc<T> as core::ops::drop::Drop>::drop::h30c9788e90bfa607
  20:     0x7fea341ddd1d - core::ptr::drop_in_place<rustc_interface::interface::Compiler>::h04cee182ac6141b7
  21:     0x7fea341dd73c - rustc_span::with_source_map::h8044517cb42f9e14
  22:     0x7fea341ef1ea - rustc_interface::interface::create_compiler_and_run::h600b31664ea7498c
  23:     0x7fea341e1349 - scoped_tls::ScopedKey<T>::set::h67b78cee48afc23b
  24:     0x7fea341dd85a - std::sys_common::backtrace::__rust_begin_short_backtrace::h7d4575ab5f030af1
  25:     0x7fea341dcb95 - core::ops::function::FnOnce::call_once{{vtable.shim}}::h0e7f7efed8d1ac6c
  26:     0x7fea31f351c7 - <alloc::boxed::Box<F,A> as core::ops::function::FnOnce<Args>>::call_once::he2a466339cf4c9af
                               at /rustc/e3b1c12becebd21d88ca9f4364d7db8d1d380c18/library/alloc/src/boxed.rs:1572:9
  27:     0x7fea31f351c7 - <alloc::boxed::Box<F,A> as core::ops::function::FnOnce<Args>>::call_once::h1f2d848478877ebe
                               at /rustc/e3b1c12becebd21d88ca9f4364d7db8d1d380c18/library/alloc/src/boxed.rs:1572:9
  28:     0x7fea31f351c7 - std::sys::unix::thread::Thread::new::thread_start::h12773e412063ea14
                               at /rustc/e3b1c12becebd21d88ca9f4364d7db8d1d380c18/library/std/src/sys/unix/thread.rs:91:17
  29:     0x7fea31e6e609 - start_thread
  30:     0x7fea31d82293 - clone
  31:                0x0 - <unknown>

error: internal compiler error: unexpected panic

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 1.56.0-nightly (e3b1c12be 2021-08-02) running on x86_64-unknown-linux-gnu

note: compiler flags: -C embed-bitcode=no -C codegen-units=1 -C debuginfo=2 --crate-type bin

note: some of the compiler flags provided by cargo are hidden

query stack during panic:
end of query stack
thread panicked while panicking. aborting.
error: could not compile `playground`