ICE: Complex control flow is forbidden in a const context

[DutchGhost]

I tried this code:

#![feature(const_trait_impl, const_fn)]

pub trait MyTrait {
    fn method(&self);
}

impl const MyTrait for std::convert::Infallible {
    #[inline(always)]
    fn method(&self) {
        match *self {}
    }
}

I expected to see this happen: Report an error in compilation which tells me that I need #![feature(const_if_match)]. If that feature is enabled, this ICE DOESNT happen.

Instead, this happened: This ICE

Meta

rustc --version --verbose:

1.43.0-nightly (d3c79346a 2020-02-29)

Backtrace

warning: the feature `const_trait_impl` is incomplete and may cause the compiler to crash
 --> src/lib.rs:1:12
  |
1 | #![feature(const_trait_impl, const_fn)]
  |            ^^^^^^^^^^^^^^^^
  |
  = note: `#[warn(incomplete_features)]` on by default

error: internal compiler error: complex control flow is forbidden in a const context
  --> src/lib.rs:9:5
   |
9  | /     fn method(&self) {
10 | |         match *self {}
11 | |     }
   | |_____^

thread 'rustc' panicked at 'no errors encountered even though `delay_span_bug` issued', src/librustc_errors/lib.rs:355:17
stack backtrace:
   0: backtrace::backtrace::libunwind::trace
             at /cargo/registry/src/gh.neting.cc-1ecc6299db9ec823/backtrace-0.3.44/src/backtrace/libunwind.rs:86
   1: backtrace::backtrace::trace_unsynchronized
             at /cargo/registry/src/gh.neting.cc-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:1053
   5: std::io::Write::write_fmt
             at src/libstd/io/mod.rs:1428
   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 as core::ops::drop::Drop>::drop
  14: core::ptr::drop_in_place
  15: <alloc::rc::Rc<T> as core::ops::drop::Drop>::drop
  16: core::ptr::drop_in_place
  17: rustc_interface::interface::run_compiler_in_existing_thread_pool
  18: syntax::attr::with_globals
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/blob/master/CONTRIBUTING.md#bug-reports

note: rustc 1.43.0-nightly (d3c79346a 2020-02-29) running on x86_64-unknown-linux-gnu

note: compiler flags: -C codegen-units=1 -C debuginfo=2 --crate-type lib

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

query stack during panic:
end of query stack
error: could not compile `playground`.

[DutchGhost]

Edit:

This code ICE's as well, notice how this does have the const_if_match feature enabled.

#![feature(const_trait_impl, const_fn, const_if_match)]

pub trait MyTrait {
    fn method(&self);
}

impl const MyTrait for std::convert::Infallible {
    #[inline(always)]
    fn method(&self) {
        while let Some(_) = Option::<()>::None {}
    }
}

[ldm0]

Edit:

This code ICE's as well, notice how this does have the const_if_match feature enabled.

#![feature(const_trait_impl, const_fn, const_if_match)]

pub trait MyTrait {
    fn method(&self);
}

impl const MyTrait for std::convert::Infallible {
    #[inline(always)]
    fn method(&self) {
        while let Some(_) = Option::<()>::None {}
    }
}

@DutchGhost This additional code not ICEs anymore.

[DutchGhost]

Edit:
This code ICE's as well, notice how this does have the const_if_match feature enabled.

#![feature(const_trait_impl, const_fn, const_if_match)]

pub trait MyTrait {
    fn method(&self);
}

impl const MyTrait for std::convert::Infallible {
    #[inline(always)]
    fn method(&self) {
        while let Some(_) = Option::<()>::None {}
    }
}

@DutchGhost This additional code not ICEs anymore.

The issue has been fixed in #69642