ICE with GAT, TAIT + async{} when missing bound in the GAT. #90400
Labels
A-GATs
Area: Generic associated types (GATs)
C-bug
Category: This is a bug.
E-needs-mcve
Call for participation: This issue has a repro, but needs a Minimal Complete and Verifiable Example
E-needs-test
Call for participation: An issue has been fixed and does not reproduce, but no test has been added.
F-generic_associated_types
`#![feature(generic_associated_types)]` a.k.a. GATs
F-type_alias_impl_trait
`#[feature(type_alias_impl_trait)]`
GATs-triaged
Issues using the `generic_associated_types` feature that have been triaged
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
|
Interesting. So, the problem here is that the type of |
|
Update: the below examples are no longer ICEs. Some "reductions" that should have the same root cause as described above, although they error slightly differently (they all produce some kind of complaint that Using closures instead of async: #![feature(generic_associated_types)]
#![feature(type_alias_impl_trait)]
trait Bar {
fn bar(&self);
}
trait Foo {
type FooFn<B>: FnOnce();
fn foo<B: Bar>(&self, bar: B) -> Self::FooFn<B>;
}
struct MyFoo;
impl Foo for MyFoo {
type FooFn<B> = impl FnOnce();
fn foo<B: Bar>(&self, bar: B) -> Self::FooFn<B> {
move || { bar.bar() }
}
}
fn main() {
let boom: <MyFoo as Foo>::FooFn<u32> = unsafe { core::mem::zeroed() };
boom();
}OutputUsing a custom trait instead of #![feature(generic_associated_types)]
#![feature(type_alias_impl_trait)]
trait Bar {
fn bar(&self);
}
trait Baz {
fn baz(&self);
}
trait Foo {
type FooFn<B>: Baz;
fn foo<B: Bar>(&self, bar: B) -> Self::FooFn<B>;
}
struct MyFoo;
impl Foo for MyFoo {
type FooFn<B> = impl Baz;
fn foo<B: Bar>(&self, bar: B) -> Self::FooFn<B> {
MyBaz(bar)
}
}
struct MyBaz<B: Bar>(B);
impl <B: Bar> Baz for MyBaz<B> {
fn baz(&self) {}
}
fn main() {
let boom: <MyFoo as Foo>::FooFn<u32> = unsafe { core::mem::zeroed() };
boom.baz();
}Output |
|
If you use a non-associated type alias instead of a GAT, the async and |
|
GATs issue triage: not blocking. Given that there are similar repros without GATs, this basically confirms my suspicion that this isn't a GAT issue, but a TAIT one. |
|
The custom trait version no longer ICEs since #90948, the rest still do |
|
Triage: All the examples on the comment (#90400 (comment)) are no longer ICE, I'm going to mark as |
JohnTitor
added a commit
to JohnTitor/rust
that referenced
this issue
May 23, 2022
|
Triage: the original code still triggers an ICE. In #97309, I've added some tests based on #90400 (comment). |
Dylan-DPC
added a commit
to Dylan-DPC/rust
that referenced
this issue
May 23, 2022
…rrors Add some regression tests for rust-lang#90400 This adds two regression tests taken from rust-lang#90400 (comment). Note that we cannot close the issue right now as the [original code](rust-lang#90400 (comment)) still triggers an ICE. r? `@compiler-errors`
bors
added a commit
to rust-lang-ci/rust
that referenced
this issue
May 23, 2022
Rollup of 4 pull requests Successful merges: - rust-lang#96129 (Document rounding for floating-point primitive operations and string parsing) - rust-lang#97286 (Add new eslint rule to prevent whitespace before function call paren) - rust-lang#97292 (Lifetime variance fixes for rustc) - rust-lang#97309 (Add some regression tests for rust-lang#90400) Failed merges: r? `@ghost` `@rustbot` modify labels: rollup
|
The original doesn't ICE anymore on playground, it reports a few errors, but fixing them produces no ICEs at any stage |
|
any reason why this is not closed yet? we do have tests for this inside rustc |
Sign up for free
to join this conversation on GitHub.
Already have an account?
Sign in to comment
Code
I think the cause is the code is incorrect: FooFuture should require
where B: Bar. It doesn't, somehow the compiler doesn't catch this, and then ICEs at codegen if you try to useFooFuture<u32>because u32 is not Bar.playground
Meta
rustc --version --verbose:Error output
Backtrace
The text was updated successfully, but these errors were encountered: