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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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2
compiler/rustc_infer/src/infer/error_reporting/nice_region_error/static_impl_trait.rs
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@ -544,7 +544,7 @@ pub struct TraitObjectVisitor(pub FxHashSet<DefId>);
impl<'tcx> TypeVisitor<'tcx> for TraitObjectVisitor {
fn visit_ty(&mut self, t: Ty<'tcx>) -> ControlFlow<Self::BreakTy> {
match t.kind() {
ty::Dynamic(preds, re) if re.is_static() => {
ty::Dynamic(preds, re, _) if re.is_static() => {
if let Some(def_id) = preds.principal_def_id() {
self.0.insert(def_id);
}