Commits on Mar 20, 2024

1. compiler: allow transmute of ZST arrays with generics …

   Extend the `SizeSkeleton` evaluator to shortcut zero-sized arrays, thus
   considering `[T; 0]` to have a compile-time fixed-size of 0.
   
   The existing evaluator already deals with generic arrays under the
   feature-guard `transmute_const_generics`. However, it merely allows
   comparing fixed-size types with fixed-size types, and generic types with
   generic types. For generic types, it merely compares whether their
   arguments match (ordering them first). Even if their exact sizes are not
   known at compile time, it can ensure that they will eventually be the
   same.
   
   This patch extends this by shortcutting the size-evaluation of zero
   sized arrays and thus allowing size comparisons of `()` with `[T; 0]`,
   where one contains generics and the other does not.
   
   This code is guarded by `transmute_const_generics` (rust-lang#109929), even
   though it is unclear whether it should be. However, this assumes that a
   separate stabilization PR is required to move this out of the feature
   guard.
   
   Initially reported in rust-lang#98104.

   

   dvdhrm committed Mar 20, 2024
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