error: internal compiler error: src/librustc/ty/subst.rs:611: type parameter B/#2 (B/2) out of range when substituting (root type=Some((B,))) substs=[ReEarlyBound(0, 'a)]
#67844
Assignees
Labels
C-bug
Category: This is a bug.
F-type_alias_impl_trait
`#[feature(type_alias_impl_trait)]`
glacier
ICE tracked in rust-lang/glacier.
I-ICE
Issue: The compiler panicked, giving an Internal Compilation Error (ICE) ❄️
P-medium
Medium priority
T-compiler
Relevant to the compiler team, which will review and decide on the PR/issue.
Comments
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Minimized: type Curried<A> = impl std::ops::Deref<Target = impl FnOnce(A)>;
fn curry() -> Curried<()> {
Box::new(drop)
}
fn main() {} |
Centril
added
I-ICE
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Ah, neat, so it has nothing to do with closures or Fn traits. //#![feature(type_alias_impl_trait)]
trait WithAssoc { type AssocType; }
trait WithParam<A> {}
type Return<A> = impl WithAssoc<AssocType = impl WithParam<A>>;
fn my_fun() -> Return<()> {}
fn main() {} |
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T-compiler triage: I'm going to assume from @matthewjasper 's self-assignment that this does not require discussion at T-compiler meeting. Removing I-nominated label. |
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Are nested type-alias-impl-traits even allowed by the RFC? If not, we should check and emit an error we we construct the type. |
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They are |
Dylan-DPC-zz
pushed a commit
to Dylan-DPC-zz/rust
that referenced
this issue
Feb 13, 2020
…atthewjasper Properly use parent generics for opaque types Fixes rust-lang#67844 Previously, opaque types would only get parent generics if they a return-position-impl-trait (e.g. `fn foo<A>() -> impl MyTrait<A>`). However, it's possible for opaque types to be nested inside one another: ```rust trait WithAssoc { type AssocType; } trait WithParam<A> {} type Return<A> = impl WithAssoc<AssocType = impl WithParam<A>>; ``` When this occurs, we need to ensure that the nested opaque types properly inherit generic parameters from their parent opaque type. This commit fixes the `generics_of` query to take the parent item into account when determining the generics for an opaque type.
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@Aaron1011 any ideas how I can get my original example running though? fn curry<'a, A: 'a, B, C, F: Fn(A, B) -> C> (f: &'a F)
-> impl Fn<(A,), Output = impl FnOnce(B) -> C + 'a> + 'a
{
move |a| move |b| f(a,b)
}and wanted to give a name to its return type. type Curried<'a, A: 'a, B, C, F: Fn(A, B) -> C>
= impl Fn<(A,), Output = impl FnOnce(B) -> C + 'a> + 'a;
fn curry<'a, A: 'a, B, C, F: Fn(A, B) -> C> (f: &'a F)
-> Curried<'a, A, B, C, F>
{
move |a| move |b| f(a,b)
}But the compiler is still unhappy with lifetimes currently, after your fix. I'm getting the following. At least it works without the lifetimes (i.e. after removing parametrization over 'a and replacing all occurrences of 'a with 'static). |
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@Aaron1011 #![feature(type_alias_impl_trait)]
trait SomeTrait where {}
trait WithAssoc<A> where {
type AssocType;
}
type Return<A> // 'a is not in scope
= impl WithAssoc<A, AssocType = impl SomeTrait + 'a>;
fn my_fun() -> Return<()> {}
fn main() {}which didn't panic on the latest nightly (2020-02-13). Message is: |
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@steffahn: Can you open separate issues for each of those problems? |
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@Aaron1011 Okay, done ^^ (#69136, #69137) |
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Uncommenting the features and running in Nightly makes the complaints about unstable features go away while the panick stays.
I’m not sure yet how to make a smaller example out of this.smaller examples in comments belowThis code was a step of me trying out if I could turn this working code (link) into a trait to get method syntax.
(Playground)
Errors:
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