Post lazy normalization for consts cleanup (#71973) #72129

Activity

1. lcnr commented on May 12, 2020

   

   lcnr

   on May 12, 2020

   Last edited by lcnr

   ContributorAuthor

   More actions

   done

   Add src/test/ui/const-generics/issues/issue-69654.rs back in, which causes an unrelated stack overflow once lazy normalization is enabled.

   #![feature(const_generics)]
   #![allow(incomplete_features)]
   
   trait Bar<T> {}
   impl<T> Bar<T> for [u8; T] {}
   //~^ ERROR expected value, found type parameter `T`
   
   struct Foo<const N: usize> {}
   impl<const N: usize> Foo<N>
   where
       [u8; N]: Bar<[(); N]>,
   {
       fn foo() {}
   }
   
   fn main() {
       Foo::foo();
   }

   Also add the following similar test, which should compile but also causes a stack overflow.

   // run-pass
   #![feature(const_generics)]
   #![allow(incomplete_features, unused_braces)]
   
   trait Bar<T> {}
   impl<T> Bar<T> for [u8; {7}] {}
   
   struct Foo<const N: usize> {}
   impl<const N: usize> Foo<N>
   where
       [u8; N]: Bar<[(); N]>,
   {
       fn foo() {}
   }
   
   fn main() {
       Foo::foo();
   }
2. lcnr

   added

   A-const-genericsArea: const generics (parameters and arguments)Area: const generics (parameters and arguments)

   A-lazy-normalizationArea: Lazy normalization (tracking issue: #60471)Area: Lazy normalization (tracking issue: #60471)

   F-const_generics`#![feature(const_generics)]``#![feature(const_generics)]`

   on May 12, 2020
3. lcnr commented on May 12, 2020

   

   lcnr

   on May 12, 2020

   ContributorAuthor

   More actions

   Taken from a comment by @nikomatsakis

   // run-pass
   #![feature(const_generics)]
   #![feature(lazy_normalization_consts)]
   #![allow(incomplete_features)]
   
   // try to devise a test for higher-ranked case
   //
   // e.g., for<'a> EqZero<<() as Zero<'a>::C>>
   //
   //
   
   trait EqZero<const C: usize> { }
   
   impl EqZero<0> for () { }
   
   trait Zero<'a> {
       const C: usize;
   }
   
   impl<'a> Zero<'a> for () {
       const C: usize = 0;
   }
   
   fn test_me<T>()
   where for<'a> T: EqZero<{<() as Zero<'a>>::C}>
   {
   }
   
   fn main() {
       test_me::<()>();
   }

   However, that test continues to ICE even with these changes, due to some assertion in type checking. So maybe it's fine, and we should just move that test to a follow-up issue. Anyway, this code as it is written here is the code we want eventually -- we just have to reconcile some details of the leak-check first.
4. jonas-schievink

   added

   T-compilerRelevant to the compiler team, which will review and decide on the PR/issue.Relevant to the compiler team, which will review and decide on the PR/issue.

   on May 12, 2020
5. varkor commented on Oct 2, 2020

   

   varkor

   on Oct 2, 2020

   Contributor

   More actions

   Linking the relevant Zulip conversation here, which is helpful.
6. lcnr

   added

   F-lazy_normalization_consts

   on Oct 25, 2020
7. BoxyUwU

   added

   F-generic_const_exprs`#![feature(generic_const_exprs)]``#![feature(generic_const_exprs)]`

   and removed

   F-lazy_normalization_consts

   F-const_generics`#![feature(const_generics)]``#![feature(const_generics)]`

   on Sep 5, 2021
8. lcnr

   closed this as completedon Jun 24, 2022
9. lcnr commented on Jun 24, 2022

   

   lcnr

   on Jun 24, 2022

   ContributorAuthor

   More actions

   the remaining work is tracked in different issues, most notably rust-lang/project-const-generics#35