Using Self::default() instead of TypeAlias::default() causes an ICE on nightly.

[rodrimati1992]

In the process of adding my project to travis-ci I got a nightly ICE from using "Self::default() instead of TypeAlias::default()" inside an impl block for type aliases.This works fine on stable.

This is the log for the first error:
https://travis-ci.org/rodrimati1992/type_level/jobs/436599429

This is the log for the second error:
https://travis-ci.org/rodrimati1992/type_level/jobs/436607478

This are the changes made to add the project to travis-ci,
including the commits that fix the error in my project:
rodrimati1992/type_level@9411158

The files that were changed to fix the error were :

• type_level_examples/src/bin/_03_vis_wrapper.rs

• type_level_examples/src/bin/_07_split_mut.rs

[estebank]

Could you help us narrow down which nightly introduced the problem for you? How recently were you able to build before the current issue?

Particularly, I'm intrigued by #53751, namely nightly from September 12th vs 14th and #54346 September 19th vs 21st.

[estebank]

Nevermind, I believe I found the culprit https://github.com/rust-lang/rust/pull/52568/files#diff-2c49ea48a32b1e12546e0517e544ef58R315

@oli-obk can you take a look? I'm not sure I understand why we're panicing in that case instead of always emitting or at least cancelling those diagnostics.

[rodrimati1992]

I will try this in those nightlys anyway and report which ones break.

[rodrimati1992]

I tested on the rust nightly versions listed bellow on
the commit (41393e6e0e23a093709c6661ccc728ae07c621ec)

Works fine in nightly-2018-08-19-i686-unknown-linux-gnu .
Works fine in nightly-2018-08-25-i686-unknown-linux-gnu .
On nightly-2018-08-26-i686-unknown-linux-gnu I get the same error as the first comment.
On nightly-2018-08-28-i686-unknown-linux-gnu I get the same error as the first comment.
On nightly-2018-08-30-i686-unknown-linux-gnu I get the same error as the first comment.
On nightly-2018-09-01-i686-unknown-linux-gnu I get the same error as the first comment.
On nightly-2018-09-10-i686-unknown-linux-gnu I get the same error as the first comment.
On nightly-2018-09-12-i686-unknown-linux-gnu I get the same error as the first comment.
On nightly-2018-09-14-i686-unknown-linux-gnu I get the same error as the first comment.
On nightly-2018-09-19-i686-unknown-linux-gnu I get the same error as the first comment.

The output is long enough that I appended some files with their output.

2018-08-26-error.txt
2018-08-28-error.txt
2018-08-30-error.txt
2018-09-01-error.txt
2018-09-10-error.txt
2018-09-12-error.txt
2018-09-14-error.txt
2018-09-19-error.txt

[oli-obk]

The actual error is

error: internal compiler error: broken MIR in DefId(0/0:10 ~ _03_vis_wrapper[21d9]::rectangle[0]::{{impl}}[0]::new[0]) (const std::default::Default::default): bad constant user type Canonical { variables: [], value: fn() -> rectangle::RectangleInner<type_level_values::const_wrapper::ConstWrapper<<type_level_RectangleAcessible::ConstRectangleAcessible<type_level_values::reexports::Void, type_level_values::reexports::Void> as type_level_values::field_traits::SetField_<type_level_RectangleAcessible::__fields::All, type_level_Accessibility::Accessible>>::Output, type_level_values::const_wrapper::PhantomKind>> {<rectangle::RectangleInner<type_level_values::const_wrapper::ConstWrapper<<type_level_RectangleAcessible::ConstRectangleAcessible<type_level_values::reexports::Void, type_level_values::reexports::Void> as type_level_values::field_traits::SetField_<type_level_RectangleAcessible::__fields::All, type_level_Accessibility::Accessible>>::Output, type_level_values::const_wrapper::PhantomKind>> as std::default::Default>::default} } vs fn() -> rectangle::RectangleInner<type_level_values::const_wrapper::ConstWrapper<type_level_RectangleAcessible::ConstRectangleAcessible<type_level_Accessibility::Accessible, type_level_Accessibility::Accessible>, type_level_values::const_wrapper::PhantomKind>> {<rectangle::RectangleInner<type_level_values::const_wrapper::ConstWrapper<type_level_RectangleAcessible::ConstRectangleAcessible<type_level_Accessibility::Accessible, type_level_Accessibility::Accessible>, type_level_values::const_wrapper::PhantomKind>> as std::default::Default>::default}: NoSolution
  --> type_level_examples/src/bin/_03_vis_wrapper.rs:42:13                                             
   |                                                                                                   
42 |             Self::default()                                                                       
   | 

The panic! quoted in https://github.com/rust-lang/rust/pull/52568/files#diff-2c49ea48a32b1e12546e0517e544ef58R315 is just a way to abort the compiler after dumping all the ICEs

[Centril]

@rodrimati1992 Could you produce a minimal example for this? Also, does it reproduce on the current nightly?

[rodrimati1992]

I'll leave it at can't reproduce with a minimal example,I tried to but couldn't.

I haven't touched the type_level repository since december 2018(nor used it),and the type_level_values crate hasn't been able to compile due to recursive impl errors since then,so the documentation example that triggers this ICE wouldn't run anyway.