ICE: BoundRegion { var: 0, kind: BrNamed(DefId(0:9 ~ rust_bug[3fc9]::or::'a), 'a) } is a region but value is Type(_) #91801
Labels
C-bug
Category: This is a bug.
glacier
ICE tracked in rust-lang/glacier.
I-ICE
Issue: The compiler panicked, giving an Internal Compilation Error (ICE) ❄️
T-compiler
Relevant to the compiler team, which will review and decide on the PR/issue.
Comments
cfcosta
added
C-bug
fn or<'a>(first: &'static (dyn Fn(&'a i32))) -> dyn Fn(&'a i32) {
return Box::new(panic!());
}This ICEs in the playground, but interestingly, this does not fn or<'a>(first: &'static (dyn Fn(&'a i32))) -> dyn Fn(&'a i32) {
Box::new(panic!())
}Also, the |
|
also... trait Foo<'a> {}
fn or<'a>(first: &'static dyn Foo<'a>) -> dyn Foo<'a> {
return Box::new(panic!());
}also ICEs but it's a different ICE. Fun! I'll go report that. |
|
Reported that ICE as #91803, the root cause might be similar. |
|
Thanks for all the help @5225225! |
|
Bisected this Looks like is the new error. |
This was referenced Dec 24, 2021
Closed
Dylan-DPC
added a commit
to Dylan-DPC/rust
that referenced
this issue
Apr 4, 2022
Fix late-bound ICE in `dyn` return type suggestion
This fixes the root-cause of the attached issues -- the root problem is that we're using the return type from a signature with late-bound instead of early-bound regions. The change on line 1087 (`let Some(liberated_sig) = typeck_results.liberated_fn_sigs().get(fn_hir_id) else { return false; };`) makes sure we're grabbing the _right_ return type for this suggestion to check the `dyn` predicates with.
Fixes rust-lang#91801
Fixes rust-lang#91803
This fix also includes some drive-by changes, specifically:
1. Don't suggest boxing when we have `-> dyn Trait` and are already returning `Box<T>` where `T: Trait` (before we always boxed the value).
2. Suggestion applies even when the return type is a type alias (e.g. `type Foo = dyn Trait`). This does cause the suggestion to expand to the aliased type, but I think it's still beneficial.
3. Split up the multipart suggestion because there's a 6-line max in the printed output...
I am open to splitting out the above changes, if we just want to fix the ICE first.
cc: `@terrarier2111` and rust-lang#92289
Dylan-DPC
added a commit
to Dylan-DPC/rust
that referenced
this issue
Apr 4, 2022
Fix late-bound ICE in `dyn` return type suggestion
This fixes the root-cause of the attached issues -- the root problem is that we're using the return type from a signature with late-bound instead of early-bound regions. The change on line 1087 (`let Some(liberated_sig) = typeck_results.liberated_fn_sigs().get(fn_hir_id) else { return false; };`) makes sure we're grabbing the _right_ return type for this suggestion to check the `dyn` predicates with.
Fixes rust-lang#91801
Fixes rust-lang#91803
This fix also includes some drive-by changes, specifically:
1. Don't suggest boxing when we have `-> dyn Trait` and are already returning `Box<T>` where `T: Trait` (before we always boxed the value).
2. Suggestion applies even when the return type is a type alias (e.g. `type Foo = dyn Trait`). This does cause the suggestion to expand to the aliased type, but I think it's still beneficial.
3. Split up the multipart suggestion because there's a 6-line max in the printed output...
I am open to splitting out the above changes, if we just want to fix the ICE first.
cc: ``@terrarier2111`` and rust-lang#92289
This was referenced Apr 6, 2022
Sign up for free
to join this conversation on GitHub.
Already have an account?
Sign in to comment
I don't have much context on this, was doing some thinkering on what would be the best way to do something not really interesting, and got this ICE. This bug happens on both Nightly and Stable.
Code
This is the original code I managed to replicate the issue:
This code fails with the ICE error. Removing the
returnon the Box of theorfunction turns it from an ICE to a normal compiler error.A member on the Rust discord (@5225225) also reported that this, more minimal test case also returns the same error:
Meta
rustc +nightly --version --verbose:rustc +stable --version --verbose:Error output
Backtrace
The text was updated successfully, but these errors were encountered: