Internal compiler error when using Self in type definitions.

[caiopsouza]

As I commented is the issue #51994 a variant of what is not being stabilized gave me an internal compiler error.

Code:

#![feature(self_struct_ctor)]
#![allow(dead_code)]

enum Foo {}

impl Foo {
    fn bar() {
        Self(1u8);
    }
}

fn main() {}

Compiler output:

C:/Users/Caio/.cargo/bin/cargo.exe run --package nespera --bin nespera
   Compiling nespera v0.1.0 (C:\Users\Caio\projects\nespera)
error: internal compiler error: cat_expr Errd
 --> src\main.rs:7:14
  |
7 |       fn bar() {
  |  ______________^
8 | |         Self(1u8);
9 | |     }
  | |_____^

error: internal compiler error: cat_expr Errd
 --> src\main.rs:8:9
  |
8 |         Self(1u8);
  |         ^^^^^^^^^

error: internal compiler error: cat_expr Errd
 --> src\main.rs:8:9
  |
8 |         Self(1u8);
  |         ^^^^

error: internal compiler error: QualifyAndPromoteConstants: Mir had errors
 --> src\main.rs:7:5
  |
7 | /     fn bar() {
8 | |         Self(1u8);
9 | |     }
  | |_____^

error: internal compiler error: broken MIR in DefId(0/0:5 ~ nespera[1ed1]::{{impl}}[0]::bar[0]) ("return type"): bad type [type error]
 --> src\main.rs:7:5
  |
7 | /     fn bar() {
8 | |         Self(1u8);
9 | |     }
  | |_____^

error: internal compiler error: broken MIR in DefId(0/0:5 ~ nespera[1ed1]::{{impl}}[0]::bar[0]) (LocalDecl { mutability: Mut, is_user_variable: None, internal: false, is_block_tail: None, ty: [type error], user_ty: UserTypeProjections { contents: [] }, name: None, source_info: SourceInfo { span: src\main.rs:7:5: 9:6, scope: scope[0] }, visibility_scope: scope[0] }): bad type [type error]
 --> src\main.rs:7:5
  |
7 | /     fn bar() {
8 | |         Self(1u8);
9 | |     }
  | |_____^

thread 'main' panicked at 'no errors encountered even though `delay_span_bug` issued', src\librustc_errors\lib.rs:334:17
stack backtrace:
   0: std::sys_common::alloc::realloc_fallback
   1: std::panicking::take_hook
   2: std::panicking::take_hook
   3: rustc::ty::structural_impls::<impl rustc::ty::context::Lift<'tcx> for rustc::ty::instance::InstanceDef<'a>>::lift_to_tcx
   4: std::panicking::rust_panic_with_hook
   5: <rustc_errors::diagnostic::SubDiagnostic as core::fmt::Debug>::fmt
   6: <rustc_errors::Handler as core::ops::drop::Drop>::drop
   7: <humantime::duration::Error as std::error::Error>::cause
   8: <humantime::duration::Error as std::error::Error>::cause
   9: <humantime::duration::Error as std::error::Error>::cause
  10: <rustc_driver::derive_registrar::Finder as rustc::hir::itemlikevisit::ItemLikeVisitor<'v>>::visit_item
  11: _rust_maybe_catch_panic
  12: rustc_driver::profile::dump
  13: rustc_driver::main
  14: <unknown>
  15: std::panicking::update_panic_count
  16: _rust_maybe_catch_panic
  17: std::rt::lang_start_internal
  18: <unknown>
  19: <unknown>
  20: BaseThreadInitThunk
  21: RtlUserThreadStart
query stack during panic:
end of query stack

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 1.32.0-nightly (1f57e4841 2018-11-23) running on x86_64-pc-windows-msvc

note: compiler flags: -C debuginfo=2 -C incremental --crate-type bin

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

error: Could not compile `nespera`.

To learn more, run the command again with --verbose.

Process finished with exit code 101

[Centril]

cc @alexreg @oli-obk

---

Reduced:

#![feature(self_struct_ctor)]

enum Foo {}

impl Foo {
    fn bar() {
        Self
    }
}

also:

#![feature(self_struct_ctor)]

enum Foo {}

impl Foo {
    fn bar() {
        Self();
    }
}

[estebank]

Possibly fixed by #56205. Verify after that PR is merged and add regression test.

[kevgrasso]

I'd like to handle the verification & test.

[alexreg]

Thanks @kevgrasso, that would be great!

[kevgrasso]

I tried compiling it with the nightly toolchain and it still panicked:

applesaucers@DESKTOP-I15PRGM:/mnt/c/Users/applesaucers/Documents/rust_test$ RUST_BACKTRACE=1 rustc +nightly i56199.rs
warning: the feature `self_struct_ctor` has been stable since 1.32.0 and no longer requires an attribute to enable
 --> i56199.rs:1:12
  |
1 | #![feature(self_struct_ctor)]
  |            ^^^^^^^^^^^^^^^^
  |
  = note: #[warn(stable_features)] on by default

warning: path statement with no effect
 --> i56199.rs:8:9
  |
8 |         Self;
  |         ^^^^^
  |
  = note: #[warn(path_statements)] on by default

error: internal compiler error: cat_expr Errd
 --> i56199.rs:7:14
  |
7 |       fn bar() {
  |  ______________^
8 | |         Self;
9 | |     }
  | |_____^

error: internal compiler error: cat_expr Errd
 --> i56199.rs:8:9
  |
8 |         Self;
  |         ^^^^

error: internal compiler error: broken MIR in DefId(0/0:5 ~ i56199[317d]::{{impl}}[0]::bar[0]) ("return type"): bad type [type error]
 --> i56199.rs:7:5
  |
7 | /     fn bar() {
8 | |         Self;
9 | |     }
  | |_____^

error: internal compiler error: broken MIR in DefId(0/0:5 ~ i56199[317d]::{{impl}}[0]::bar[0]) (LocalDecl { mutability: Mut, is_user_variable: None, internal: false, is_block_tail: None, ty: [type error], user_ty: UserTypeProjections { contents: [] }, name: None, source_info: SourceInfo { span: i56199.rs:7:5: 9:6, scope: scope[0] }, visibility_scope: scope[0] }): bad type [type error]
 --> i56199.rs:7:5
  |
7 | /     fn bar() {
8 | |         Self;
9 | |     }
  | |_____^

error: internal compiler error: QualifyAndPromoteConstants: Mir had errors
 --> i56199.rs:7:5
  |
7 | /     fn bar() {
8 | |         Self;
9 | |     }
  | |_____^

thread 'rustc' panicked at 'no errors encountered even though `delay_span_bug` issued', src/librustc_errors/lib.rs:334:17
stack backtrace:
   0: std::sys::unix::backtrace::tracing::imp::unwind_backtrace
             at src/libstd/sys/unix/backtrace/tracing/gcc_s.rs:49
   1: std::sys_common::backtrace::_print
             at src/libstd/sys_common/backtrace.rs:71
   2: std::panicking::default_hook::{{closure}}
             at src/libstd/sys_common/backtrace.rs:59
             at src/libstd/panicking.rs:211
   3: std::panicking::default_hook
             at src/libstd/panicking.rs:227
   4: rustc::util::common::panic_hook
   5: std::panicking::rust_panic_with_hook
             at src/libstd/panicking.rs:495
   6: std::panicking::begin_panic
   7: <rustc_errors::Handler as core::ops::drop::Drop>::drop
   8: core::ptr::real_drop_in_place
   9: core::ptr::real_drop_in_place
  10: core::ptr::real_drop_in_place
  11: rustc_driver::monitor::{{closure}}
  12: __rust_maybe_catch_panic
             at src/libpanic_unwind/lib.rs:102
  13: <F as alloc::boxed::FnBox<A>>::call_box
  14: std::sys::unix::thread::Thread::new::thread_start
             at /rustc/0c999ed132d67bf2520643e9bd619972cf3888ba/src/liballoc/boxed.rs:683
             at src/libstd/sys_common/thread.rs:24
             at src/libstd/sys/unix/thread.rs:90
  15: start_thread
  16: __clone
query stack during panic:
end of query stack

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 1.32.0-nightly (0c999ed13 2018-12-03) running on x86_64-unknown-linux-gnu

for the sample code:

#![feature(self_struct_ctor)]
#![allow(dead_code)]

enum Foo {}

impl Foo {
    fn bar() {
        Self;
    }
}

fn main() {}

Would you still want me to do a regression test for this, even though it's still bugged?

[estebank]

@kevgrasso we probably should fix the bug, we normally don't add tests for ICEs that haven't been fixed. CC @alexreg follow up to #56365.

[alexreg]

On a related note, this also fails (see #56611):

#![feature(self_struct_ctor)]

struct Foo {}

impl Foo {
    fn bar() {
        Self()
    }
}

with

error: internal compiler error: src/librustc/hir/def.rs:265: attempted .def_id() on invalid def: SelfCtor(DefId(0/0:4 ~ playground[6463]::{{impl}}[0]))

[alexreg]

I've fixed all of the above cases in #56225 now.

[Centril]

@alexreg should this be closed?

[estebank]

The output of the original issue is now:

error: the `Self` constructor can only be used with tuple or unit structs
 --> src/main.rs:8:9
  |
8 |         Self(1u8);
  |         ^^^^
  |
  = help: did you mean to use one of the enum's variants?