ICE: Region parameter out of range when substituting in region...

#![feature(generic_associated_types)]

struct S;

trait Trait {
    type Associated<'a>;
}

impl Trait for S {
    type Associated<'a> = &'a ();
}

fn main() {}

error: internal compiler error: librustc/ty/subst.rs:439: Region parameter out of range when substituting in region 'a (root type=Some(TestIterItem<'a>)) (index=0)

thread 'rustc' panicked at 'Box<Any>', librustc_errors/lib.rs:488:9
note: Run with `RUST_BACKTRACE=1` for a backtrace.
error: aborting due to 2 previous errors

Rust playground

Probably related: #47309

I can reproduce this with rustc 1.26.0-nightly (f5631d9ac 2018-03-24).

Generic associated types aren't implemented past syntax yet, so this is probably expected. cc #44265

This does not only happen with generic associated lifetimes but with any generic associated type:

#![feature(generic_associated_types)]

pub trait MyTrait {
    type InternalType<TypeA>;
}

pub struct GenericType<TypeA> {
    _dummy: TypeA,
}

pub struct MyStruct {}

impl MyTrait for MyStruct {
    type InternalType<TypeA> = GenericType<TypeA>;
}

// -----------------------------------------------------------------------------
fn main() {}

Compiling playground v0.0.1 (file:///playground)
error: internal compiler error: librustc/ty/subst.rs:493: Type parameter `TypeA/#0` (TypeA/0) out of range when substituting (root type=Some(GenericType<TypeA>)) substs=[]

thread 'main' panicked at 'Box<Any>', librustc_errors/lib.rs:499:9
note: Run with `RUST_BACKTRACE=1` for a backtrace.
error: aborting due to previous error

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 1.27.0-nightly (565235ee7 2018-05-07) running on x86_64-unknown-linux-gnu
note: compiler flags: -C codegen-units=1 -C debuginfo=2 --crate-type bin
note: some of the compiler flags provided by cargo are hidden

Rust playground: https://play.rust-lang.org/?gist=c36f51038511f3e6568b1b2c866f2ca3&version=nightly&mode=debug

Maybe its worth to disable the feature flag or add a compiler error warning if the flag is used, until the feature implementation progressed further.

Triage: still happens.

Slightly reduced, no need for a new struct S, just use the unit type

#![feature(generic_associated_types)]

trait Trait {
    type Associated<'a>;
}

impl Trait for () {
    type Associated<'a> = &'a ();
}

fn main() {}

Closing in favor of #62521.

@estebank

@estebank although they are two different ICE messages?

error: internal compiler error: Region parameter out of range when substituting in region 'a (root type=Some(&'a ())) (index=0)

vs

error: internal compiler error: src/librustc_mir/borrow_check/nll/universal_regions.rs:764: cannot convert ReEarlyBound(0, 'a) to a region vid

Rollup merge of rust-lang#67160 - matthewjasper:gat-generics, r=nikom…

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ICE: Region parameter out of range when substituting in region... #49362

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ICE: Region parameter out of range when substituting in region... #49362

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matthewjasper commented on Mar 25, 2018

0ndorio commented on May 8, 2018

estebank commented on May 8, 2019

hellow554 commented on Nov 25, 2019

estebank commented on Nov 25, 2019

hellow554 commented on Nov 26, 2019

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