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Auto merge of #101212 - eholk:dyn-star, r=compiler-errors

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Initial implementation of dyn*

This PR adds extremely basic and incomplete support for [dyn*](https://smallcultfollowing.com/babysteps//blog/2022/03/29/dyn-can-we-make-dyn-sized/). The goal is to get something in tree behind a flag to make collaboration easier, and also to make sure the implementation so far is not unreasonable. This PR does quite a few things:

* Introduce `dyn_star` feature flag
* Adds parsing for `dyn* Trait` types
* Defines `dyn* Trait` as a sized type
* Adds support for explicit casts, like `42usize as dyn* Debug`
  * Including const evaluation of such casts
* Adds codegen for drop glue so things are cleaned up properly when a `dyn* Trait` object goes out of scope
* Adds codegen for method calls, at least for methods that take `&self`

Quite a bit is still missing, but this gives us a starting point. Note that this is never intended to become stable surface syntax for Rust, but rather `dyn*` is planned to be used as an implementation detail for async functions in dyn traits.

Joint work with `@nikomatsakis` and `@compiler-errors.`

r? `@bjorn3`
This commit is contained in:
bors 2022-09-14 18:10:51 +00:00
commit 6153d3cbe6
69 changed files with 617 additions and 104 deletions
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10
compiler/rustc_middle/src/ty/structural_impls.rs
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@ -1028,9 +1028,11 @@ impl<'tcx> TypeSuperFoldable<'tcx> for Ty<'tcx> {
ty::Array(typ, sz) => ty::Array(typ.try_fold_with(folder)?, sz.try_fold_with(folder)?),
ty::Slice(typ) => ty::Slice(typ.try_fold_with(folder)?),
ty::Adt(tid, substs) => ty::Adt(tid, substs.try_fold_with(folder)?),
ty::Dynamic(trait_ty, region) => {
ty::Dynamic(trait_ty.try_fold_with(folder)?, region.try_fold_with(folder)?)
}
ty::Dynamic(trait_ty, region, representation) => ty::Dynamic(
trait_ty.try_fold_with(folder)?,
region.try_fold_with(folder)?,
representation,
),
ty::Tuple(ts) => ty::Tuple(ts.try_fold_with(folder)?),
ty::FnDef(def_id, substs) => ty::FnDef(def_id, substs.try_fold_with(folder)?),
ty::FnPtr(f) => ty::FnPtr(f.try_fold_with(folder)?),
@ -1074,7 +1076,7 @@ impl<'tcx> TypeSuperVisitable<'tcx> for Ty<'tcx> {
}
ty::Slice(typ) => typ.visit_with(visitor),
ty::Adt(_, substs) => substs.visit_with(visitor),
ty::Dynamic(ref trait_ty, ref reg) => {
ty::Dynamic(ref trait_ty, ref reg, _) => {
trait_ty.visit_with(visitor)?;
reg.visit_with(visitor)
}