rustc error while toying with Iterator and yield

[ulodciv]

Code

fn iter_call() -> impl Iterator<Item = String> {
    yield foo
}

fn main() {
}

Meta

rustc --version --verbose:

rustc 1.58.0 (02072b482 2022-01-11)
binary: rustc
commit-hash: 02072b482a8b5357f7fb5e5637444ae30e423c40
commit-date: 2022-01-11
host: x86_64-unknown-linux-gnu
release: 1.58.0
LLVM version: 13.0.0

Error output

[foo1]$ cargo build
   Compiling foo1 v0.1.0 (/foo1)
error[E0425]: cannot find value `foo` in this scope
 --> src/main.rs:2:11
  |
2 |     yield foo
  |           ^^^ not found in this scope

error[E0658]: yield syntax is experimental
 --> src/main.rs:2:5
  |
2 |     yield foo
  |     ^^^^^^^^^
  |
  = note: see issue #43122 <https://github.com/rust-lang/rust/issues/43122> for more information

error[E0627]: yield expression outside of generator literal
 --> src/main.rs:2:5
  |
2 |     yield foo
  |     ^^^^^^^^^

error[E0277]: `()` is not an iterator
 --> src/main.rs:1:19
  |
1 | fn iter_call() -> impl Iterator<Item = String> {
  |                   ^^^^^^^^^^^^^^^^^^^^^^^^^^^^ `()` is not an iterator
  |
  = help: the trait `Iterator` is not implemented for `()`

thread 'rustc' panicked at 'assertion failed: body.yield_ty().is_some() == universal_regions.yield_ty.is_some()', compiler/rustc_borrowck/src/type_check/input_output.rs:120:9
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 1.58.0 (02072b482 2022-01-11) running on x86_64-unknown-linux-gnu

note: compiler flags: -C embed-bitcode=no -C debuginfo=2 -C incremental --crate-type bin

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

query stack during panic:
#0 [mir_borrowck] borrow-checking `iter_call`
#1 [type_of] computing type of `iter_call::{opaque#0}`
end of query stack
Some errors have detailed explanations: E0277, E0425, E0627, E0658.
For more information about an error, try `rustc --explain E0277`.
error: could not compile `foo1` due to 4 previous errors

Backtrace

   Compiling foo1 v0.1.0 /foo1)
error[E0425]: cannot find value `foo` in this scope
 --> src/main.rs:2:11
  |
2 |     yield foo
  |           ^^^ not found in this scope

error[E0658]: yield syntax is experimental
 --> src/main.rs:2:5
  |
2 |     yield foo
  |     ^^^^^^^^^
  |
  = note: see issue #43122 <https://github.com/rust-lang/rust/issues/43122> for more information

error[E0627]: yield expression outside of generator literal
 --> src/main.rs:2:5
  |
2 |     yield foo
  |     ^^^^^^^^^

error[E0277]: `()` is not an iterator
 --> src/main.rs:1:19
  |
1 | fn iter_call() -> impl Iterator<Item = String> {
  |                   ^^^^^^^^^^^^^^^^^^^^^^^^^^^^ `()` is not an iterator
  |
  = help: the trait `Iterator` is not implemented for `()`

thread 'rustc' panicked at 'assertion failed: body.yield_ty().is_some() == universal_regions.yield_ty.is_some()', compiler/rustc_borrowck/src/type_check/input_output.rs:120:9
stack backtrace:
   0: rust_begin_unwind
             at /rustc/02072b482a8b5357f7fb5e5637444ae30e423c40/library/std/src/panicking.rs:498:5
   1: core::panicking::panic_fmt
             at /rustc/02072b482a8b5357f7fb5e5637444ae30e423c40/library/core/src/panicking.rs:107:14
   2: core::panicking::panic
             at /rustc/02072b482a8b5357f7fb5e5637444ae30e423c40/library/core/src/panicking.rs:48:5
   3: rustc_borrowck::type_check::type_check
   4: rustc_borrowck::nll::compute_regions
   5: rustc_borrowck::do_mir_borrowck
   6: <rustc_infer::infer::InferCtxtBuilder>::enter::<rustc_middle::mir::query::BorrowCheckResult, rustc_borrowck::mir_borrowck::{closure#0}>
   7: rustc_borrowck::mir_borrowck
   8: <rustc_borrowck::provide::{closure#0} as core::ops::function::FnOnce<(rustc_middle::ty::context::TyCtxt, rustc_span::def_id::LocalDefId)>>::call_once
   9: <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::mir::query::BorrowCheckResult>
  10: rustc_data_structures::stack::ensure_sufficient_stack::<(&rustc_middle::mir::query::BorrowCheckResult, 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::mir::query::BorrowCheckResult>::{closure#3}>
  11: 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::mir::query::BorrowCheckResult>>
  12: rustc_query_system::query::plumbing::get_query::<rustc_query_impl::queries::mir_borrowck, rustc_query_impl::plumbing::QueryCtxt>
  13: rustc_typeck::collect::type_of::type_of
  14: <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::DefId, &rustc_middle::ty::TyS>
  15: rustc_data_structures::stack::ensure_sufficient_stack::<(&rustc_middle::ty::TyS, rustc_query_system::dep_graph::graph::DepNodeIndex), rustc_query_system::query::plumbing::execute_job<rustc_query_impl::plumbing::QueryCtxt, rustc_span::def_id::DefId, &rustc_middle::ty::TyS>::{closure#3}>
  16: rustc_query_system::query::plumbing::try_execute_query::<rustc_query_impl::plumbing::QueryCtxt, rustc_query_system::query::caches::DefaultCache<rustc_span::def_id::DefId, &rustc_middle::ty::TyS>>
  17: <rustc_query_impl::Queries as rustc_middle::ty::query::QueryEngine>::type_of
  18: rustc_typeck::check::check::check_item_type
  19: <rustc_middle::hir::map::Map>::visit_item_likes_in_module::<rustc_typeck::check::CheckItemTypesVisitor>
  20: rustc_typeck::check::check::check_mod_item_types
  21: <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, ()>
  22: rustc_data_structures::stack::ensure_sufficient_stack::<((), rustc_query_system::dep_graph::graph::DepNodeIndex), rustc_query_system::query::plumbing::execute_job<rustc_query_impl::plumbing::QueryCtxt, rustc_span::def_id::LocalDefId, ()>::{closure#3}>
  23: rustc_query_system::query::plumbing::try_execute_query::<rustc_query_impl::plumbing::QueryCtxt, rustc_query_system::query::caches::DefaultCache<rustc_span::def_id::LocalDefId, ()>>
  24: rustc_query_system::query::plumbing::get_query::<rustc_query_impl::queries::check_mod_item_types, rustc_query_impl::plumbing::QueryCtxt>
  25: <rustc_middle::hir::map::Map>::for_each_module::<rustc_typeck::check_crate::{closure#6}::{closure#0}>
  26: rustc_typeck::check_crate
  27: rustc_interface::passes::analysis
  28: <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>>
  29: 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}>
  30: 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>>>
  31: <rustc_query_impl::Queries as rustc_middle::ty::query::QueryEngine>::analysis
  32: <rustc_interface::passes::QueryContext>::enter::<rustc_driver::run_compiler::{closure#1}::{closure#2}::{closure#3}, core::result::Result<(), rustc_errors::ErrorReported>>
  33: <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>>
  34: 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}>
  35: <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>>
note: Some details are omitted, run with `RUST_BACKTRACE=full` for a verbose 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 1.58.0 (02072b482 2022-01-11) running on x86_64-unknown-linux-gnu

note: compiler flags: -C embed-bitcode=no -C debuginfo=2 -C incremental --crate-type bin

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

query stack during panic:
#0 [mir_borrowck] borrow-checking `iter_call`
#1 [type_of] computing type of `iter_call::{opaque#0}`
#2 [check_mod_item_types] checking item types in top-level module
#3 [analysis] running analysis passes on this crate
end of query stack
Some errors have detailed explanations: E0277, E0425, E0627, E0658.
For more information about an error, try `rustc --explain E0277`.
error: could not compile `foo1` due to 4 previous errors

[compiler-errors]

I fixed this in #91488, which should be on the latest nightly.