Stable rust throws an internal compiler error (ICE) that appears to be related to type inference surrounding higher rank trait bounds (HRTBs) and associated types.
Code:
playground
trait Parser<'s> {
type Output;
fn call(&self, input: &'s str) -> (&'s str, Self::Output);
}
impl<'s, F, T> Parser<'s> for F
where F: Fn(&'s str) -> (&'s str, T) {
type Output = T;
fn call(&self, input: &'s str) -> (&'s str, T) {
self(input)
}
}
fn foo<F1, F2>(
f1: F1,
base: &'static str,
f2: F2
)
where
F1: for<'a> Parser<'a>,
F2: FnOnce(&<F1 as Parser>::Output) -> bool
{
let s: String = base.to_owned();
let str_ref = s.as_ref();
let (remaining, produced) = f1.call(str_ref);
assert!(f2(&produced));
assert_eq!(remaining.len(), 0);
}
struct Wrapper<'a>(&'a str);
fn main() {
fn bar<'a>(s: &'a str) -> (&'a str, &'a str) {
(&s[..1], &s[..])
}
fn baz<'a>(s: &'a str) -> (&'a str, Wrapper<'a>) {
(&s[..1], Wrapper(&s[..]))
}
foo(bar, "string", |s| s.len() == 5);
foo(baz, "string", |s| s.0.len() == 5);
}Expectaions:
I expected this code to compile and run smoothly, without throwing any errors at compile time or runtime.
Result
Instead, this happened:
Compiling playground v0.0.1 (/playground)
error: internal compiler error: src/librustc_infer/traits/codegen/mod.rs:61: Encountered error `OutputTypeParameterMismatch(Binder(<[closure@src/main.rs:43:24: 43:40] as std::ops::FnOnce<(&<for<'a> fn(&'a str) -> (&'a str, &'a str) {main::bar} as Parser<'_>>::Output,)>>), Binder(<[closure@src/main.rs:43:24: 43:40] as std::ops::FnOnce<(&&str,)>>), Sorts(ExpectedFound { expected: &str, found: <for<'a> fn(&'a str) -> (&'a str, &'a str) {main::bar} as Parser<'_>>::Output }))` selecting `Binder(<[closure@src/main.rs:43:24: 43:40] as std::ops::FnOnce<(&&str,)>>)` during codegen
thread 'rustc' panicked at 'Box<Any>', src/librustc_errors/lib.rs:875:9
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/blob/master/CONTRIBUTING.md#bug-reports
note: rustc 1.43.0 (4fb7144ed 2020-04-20) running on x86_64-unknown-linux-gnu
note: compiler flags: -C codegen-units=1 -C debuginfo=2 --crate-type bin
note: some of the compiler flags provided by cargo are hidden
error: aborting due to previous error
error: could not compile `playground`.
To learn more, run the command again with --verbose.
Meta
Rust version: this is running on the playground on the stable version.
On my local machine (which gives the same output) rust --version --verbose:
rustc 1.43.0 (4fb7144ed 2020-04-20)
binary: rustc
commit-hash: 4fb7144ed159f94491249e86d5bbd033b5d60550
commit-date: 2020-04-20
host: x86_64-unknown-linux-gnu
release: 1.43.0
LLVM version: 9.0
Backtrace (on playground):
Compiling playground v0.0.1 (/playground)
error: internal compiler error: src/librustc_infer/traits/codegen/mod.rs:61: Encountered error `OutputTypeParameterMismatch(Binder(<[closure@src/main.rs:43:24: 43:40] as std::ops::FnOnce<(&<for<'a> fn(&'a str) -> (&'a str, &'a str) {main::bar} as Parser<'_>>::Output,)>>), Binder(<[closure@src/main.rs:43:24: 43:40] as std::ops::FnOnce<(&&str,)>>), Sorts(ExpectedFound { expected: &str, found: <for<'a> fn(&'a str) -> (&'a str, &'a str) {main::bar} as Parser<'_>>::Output }))` selecting `Binder(<[closure@src/main.rs:43:24: 43:40] as std::ops::FnOnce<(&&str,)>>)` during codegen
thread 'rustc' panicked at 'Box<Any>', src/librustc_errors/lib.rs:875:9
stack backtrace:
0: backtrace::backtrace::libunwind::trace
at /cargo/registry/src/github.com-1ecc6299db9ec823/backtrace-0.3.44/src/backtrace/libunwind.rs:86
1: backtrace::backtrace::trace_unsynchronized
at /cargo/registry/src/github.com-1ecc6299db9ec823/backtrace-0.3.44/src/backtrace/mod.rs:66
2: std::sys_common::backtrace::_print_fmt
at src/libstd/sys_common/backtrace.rs:78
3: <std::sys_common::backtrace::_print::DisplayBacktrace as core::fmt::Display>::fmt
at src/libstd/sys_common/backtrace.rs:59
4: core::fmt::write
at src/libcore/fmt/mod.rs:1063
5: std::io::Write::write_fmt
at src/libstd/io/mod.rs:1426
6: std::sys_common::backtrace::_print
at src/libstd/sys_common/backtrace.rs:62
7: std::sys_common::backtrace::print
at src/libstd/sys_common/backtrace.rs:49
8: std::panicking::default_hook::{{closure}}
at src/libstd/panicking.rs:204
9: std::panicking::default_hook
at src/libstd/panicking.rs:224
10: rustc_driver::report_ice
11: std::panicking::rust_panic_with_hook
at src/libstd/panicking.rs:474
12: std::panicking::begin_panic
13: rustc_errors::HandlerInner::bug
14: rustc_errors::Handler::bug
15: rustc::util::bug::opt_span_bug_fmt::{{closure}}
16: rustc::ty::context::tls::with_opt::{{closure}}
17: rustc::ty::context::tls::with_opt
18: rustc::util::bug::opt_span_bug_fmt
19: rustc::util::bug::bug_fmt
20: rustc::ty::context::GlobalCtxt::enter_local
21: rustc_infer::traits::codegen::codegen_fulfill_obligation
22: rustc::ty::query::__query_compute::codegen_fulfill_obligation
23: rustc::ty::query::<impl rustc::ty::query::config::QueryAccessors for rustc::ty::query::queries::codegen_fulfill_obligation>::compute
24: rustc::dep_graph::graph::DepGraph::with_task_impl
25: rustc::ty::query::plumbing::<impl rustc::ty::context::TyCtxt>::get_query
26: rustc_ty::instance::resolve_instance
27: rustc::ty::instance::Instance::resolve
28: <rustc_mir::monomorphize::collector::MirNeighborCollector as rustc::mir::visit::Visitor>::visit_terminator_kind
29: rustc_mir::monomorphize::collector::collect_items_rec
30: rustc_mir::monomorphize::collector::collect_items_rec
31: rustc_session::utils::<impl rustc_session::session::Session>::time
32: rustc_mir::monomorphize::collector::collect_crate_mono_items
33: rustc_mir::monomorphize::partitioning::collect_and_partition_mono_items
34: rustc::ty::query::__query_compute::collect_and_partition_mono_items
35: rustc::dep_graph::graph::DepGraph::with_task_impl
36: rustc::ty::query::plumbing::<impl rustc::ty::context::TyCtxt>::get_query
37: rustc_codegen_ssa::base::codegen_crate
38: <rustc_codegen_llvm::LlvmCodegenBackend as rustc_codegen_utils::codegen_backend::CodegenBackend>::codegen_crate
39: rustc_interface::passes::start_codegen
40: rustc::ty::context::tls::enter_global
41: rustc_interface::queries::Queries::ongoing_codegen
42: rustc_interface::interface::run_compiler_in_existing_thread_pool
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/blob/master/CONTRIBUTING.md#bug-reports
note: rustc 1.43.0 (4fb7144ed 2020-04-20) running on x86_64-unknown-linux-gnu
note: compiler flags: -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 [codegen_fulfill_obligation] checking if `std::ops::FnOnce` fulfills its obligations
#1 [collect_and_partition_mono_items] collect_and_partition_mono_items
end of query stack
error: aborting due to previous error
error: could not compile `playground`.
To learn more, run the command again with --verbose.
Backtrace (with verbose enabled) (on my local machine):
$ RUST_BACKTRACE=1 rustc --verbose ICE.rs
error: internal compiler error: src/librustc_infer/traits/codegen/mod.rs:61: Encountered error `OutputTypeParameterMismatch(Binder(<[closure@ICE.rs:43:24: 43:40] as std::ops::FnOnce<(&<for<'a> fn(&'a str) -> (&'a str, &'a str) {main::bar} as Parser<'_>>::Output,)>>), Binder(<[closure@ICE.rs:43:24: 43:40] as std::ops::FnOnce<(&&str,)>>), Sorts(ExpectedFound { expected: &str, found: <for<'a> fn(&'a str) -> (&'a str, &'a str) {main::bar} as Parser<'_>>::Output }))` selecting `Binder(<[closure@ICE.rs:43:24: 43:40] as std::ops::FnOnce<(&&str,)>>)` during codegen
thread 'rustc' panicked at 'Box<Any>', src/librustc_errors/lib.rs:875:9
stack backtrace:
0: backtrace::backtrace::libunwind::trace
at /cargo/registry/src/github.com-1ecc6299db9ec823/backtrace-0.3.44/src/backtrace/libunwind.rs:86
1: backtrace::backtrace::trace_unsynchronized
at /cargo/registry/src/github.com-1ecc6299db9ec823/backtrace-0.3.44/src/backtrace/mod.rs:66
2: std::sys_common::backtrace::_print_fmt
at src/libstd/sys_common/backtrace.rs:78
3: <std::sys_common::backtrace::_print::DisplayBacktrace as core::fmt::Display>::fmt
at src/libstd/sys_common/backtrace.rs:59
4: core::fmt::write
at src/libcore/fmt/mod.rs:1063
5: std::io::Write::write_fmt
at src/libstd/io/mod.rs:1426
6: std::sys_common::backtrace::_print
at src/libstd/sys_common/backtrace.rs:62
7: std::sys_common::backtrace::print
at src/libstd/sys_common/backtrace.rs:49
8: std::panicking::default_hook::{{closure}}
at src/libstd/panicking.rs:204
9: std::panicking::default_hook
at src/libstd/panicking.rs:224
10: rustc_driver::report_ice
11: std::panicking::rust_panic_with_hook
at src/libstd/panicking.rs:474
12: std::panicking::begin_panic
13: rustc_errors::HandlerInner::bug
14: rustc_errors::Handler::bug
15: rustc::util::bug::opt_span_bug_fmt::{{closure}}
16: rustc::ty::context::tls::with_opt::{{closure}}
17: rustc::ty::context::tls::with_opt
18: rustc::util::bug::opt_span_bug_fmt
19: rustc::util::bug::bug_fmt
20: rustc::ty::context::GlobalCtxt::enter_local
21: rustc_infer::traits::codegen::codegen_fulfill_obligation
22: rustc::ty::query::__query_compute::codegen_fulfill_obligation
23: rustc::ty::query::<impl rustc::ty::query::config::QueryAccessors for rustc::ty::query::queries::codegen_fulfill_obligation>::compute
24: rustc::dep_graph::graph::DepGraph::with_task_impl
25: rustc::ty::query::plumbing::<impl rustc::ty::context::TyCtxt>::get_query
26: rustc_ty::instance::resolve_instance
27: rustc::ty::instance::Instance::resolve
28: <rustc_mir::monomorphize::collector::MirNeighborCollector as rustc::mir::visit::Visitor>::visit_terminator_kind
29: rustc_mir::monomorphize::collector::collect_items_rec
30: rustc_mir::monomorphize::collector::collect_items_rec
31: rustc_session::utils::<impl rustc_session::session::Session>::time
32: rustc_mir::monomorphize::collector::collect_crate_mono_items
33: rustc_mir::monomorphize::partitioning::collect_and_partition_mono_items
34: rustc::ty::query::__query_compute::collect_and_partition_mono_items
35: rustc::dep_graph::graph::DepGraph::with_task_impl
36: rustc::ty::query::plumbing::<impl rustc::ty::context::TyCtxt>::get_query
37: rustc_codegen_ssa::base::codegen_crate
38: <rustc_codegen_llvm::LlvmCodegenBackend as rustc_codegen_utils::codegen_backend::CodegenBackend>::codegen_crate
39: rustc_interface::passes::start_codegen
40: rustc::ty::context::tls::enter_global
41: rustc_interface::queries::Queries::ongoing_codegen
42: rustc_interface::interface::run_compiler_in_existing_thread_pool
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/blob/master/CONTRIBUTING.md#bug-reports
note: rustc 1.43.0 (4fb7144ed 2020-04-20) running on x86_64-unknown-linux-gnu
query stack during panic:
#0 [codegen_fulfill_obligation] checking if `std::ops::FnOnce` fulfills its obligations
#1 [collect_and_partition_mono_items] collect_and_partition_mono_items
end of query stack
error: aborting due to previous error
Stable rust throws an internal compiler error (ICE) that appears to be related to type inference surrounding higher rank trait bounds (HRTBs) and associated types.
Code:
playground
Expectaions:
I expected this code to compile and run smoothly, without throwing any errors at compile time or runtime.
Result
Instead, this happened:
Meta
Rust version: this is running on the playground on the stable version.
On my local machine (which gives the same output)
rust --version --verbose:Backtrace (on playground):
Backtrace (with verbose enabled) (on my local machine):