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GAT ICE: cannot directly store unsized values #68656
Labels
C-bug
Category: This is a bug.
F-generic_associated_types
`#![feature(generic_associated_types)]` a.k.a. GATs
glacier
ICE tracked in rust-lang/glacier.
I-ICE
Issue: The compiler panicked, giving an Internal Compilation Error (ICE) ❄️
requires-nightly
This issue requires a nightly compiler in some way.
T-compiler
Relevant to the compiler team, which will review and decide on the PR/issue.
Comments
jonas-schievink
added
C-bug
Category: This is a bug.
F-generic_associated_types
`#![feature(generic_associated_types)]` a.k.a. GATs
I-ICE
Issue: The compiler panicked, giving an Internal Compilation Error (ICE) ❄️
requires-nightly
This issue requires a nightly compiler in some way.
T-compiler
Relevant to the compiler team, which will review and decide on the PR/issue.
labels
Jan 29, 2020
28 tasks
Manishearth
added a commit
to Manishearth/rust
that referenced
this issue
Jun 16, 2020
…dation, r=nikomatsakis Projection bound validation During selection we use bounds declared on associated types (e.g. `type X: Copy`) to satisfy trait/projection bounds. This would be fine so long as those bounds are checked on any impls/trait objects. For simple cases they are because the bound `Self::X: Copy` gets normalized when we check the impl. However, for default values with specialization and higher-ranked bounds from GATs or otherwise, we can't normalize when checking the impl, and so we use the bound from the trait to prove that the bound applies to the impl, which is clearly unsound. This PR makes 2 fixes for this: 1. Requiring that the bounds on the trait apply to a projection type with the corresponding substs, so a bound `for<'a> <Self as X<'a>>::U: Copy` on the trait cannot be used to prove `<T as X<'_>>::U: Copy`. 2. Actually checking that the bounds that we still allow apply to generic/default associated types. Opening for a crater run. Closes rust-lang#68641 Closes rust-lang#68642 Closes rust-lang#68643 Closes rust-lang#68644 Closes rust-lang#68645 Closes rust-lang#68656 r? @ghost
Manishearth
added a commit
to Manishearth/rust
that referenced
this issue
Jun 20, 2020
…dation, r=nikomatsakis Projection bound validation During selection we use bounds declared on associated types (e.g. `type X: Copy`) to satisfy trait/projection bounds. This would be fine so long as those bounds are checked on any impls/trait objects. For simple cases they are because the bound `Self::X: Copy` gets normalized when we check the impl. However, for default values with specialization and higher-ranked bounds from GATs or otherwise, we can't normalize when checking the impl, and so we use the bound from the trait to prove that the bound applies to the impl, which is clearly unsound. This PR makes 2 fixes for this: 1. Requiring that the bounds on the trait apply to a projection type with the corresponding substs, so a bound `for<'a> <Self as X<'a>>::U: Copy` on the trait cannot be used to prove `<T as X<'_>>::U: Copy`. 2. Actually checking that the bounds that we still allow apply to generic/default associated types. Opening for a crater run. Closes rust-lang#68641 Closes rust-lang#68642 Closes rust-lang#68643 Closes rust-lang#68644 Closes rust-lang#68645 Closes rust-lang#68656 r? @ghost
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Labels
C-bug
Category: This is a bug.
F-generic_associated_types
`#![feature(generic_associated_types)]` a.k.a. GATs
glacier
ICE tracked in rust-lang/glacier.
I-ICE
Issue: The compiler panicked, giving an Internal Compilation Error (ICE) ❄️
requires-nightly
This issue requires a nightly compiler in some way.
T-compiler
Relevant to the compiler team, which will review and decide on the PR/issue.
The following ICE's:
Backtrace:
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