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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 e4d2f94a83
2 changed files with 6 additions and 1 deletions
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4
src/base.rs
View File

@ -701,6 +701,10 @@ fn is_fat_ptr<'tcx>(fx: &FunctionCx<'_, '_, 'tcx>, ty: Ty<'tcx>) -> bool {
let operand = codegen_operand(fx, operand);
operand.unsize_value(fx, lval);
}
Rvalue::Cast(CastKind::DynStar, _, _) => {
// FIXME(dyn-star)
unimplemented!()
}
Rvalue::Discriminant(place) => {
let place = codegen_place(fx, place);
let value = place.to_cvalue(fx);

3
src/value_and_place.rs
View File

@ -815,7 +815,8 @@ pub(crate) fn assert_assignable<'tcx>(
);
// fn(&T) -> for<'l> fn(&'l T) is allowed
}
(&ty::Dynamic(from_traits, _), &ty::Dynamic(to_traits, _)) => {
(&ty::Dynamic(from_traits, _, _from_kind), &ty::Dynamic(to_traits, _, _to_kind)) => {
// FIXME(dyn-star): Do the right thing with DynKinds
for (from, to) in from_traits.iter().zip(to_traits) {
let from =
fx.tcx.normalize_erasing_late_bound_regions(ParamEnv::reveal_all(), from);