bjoernager/rust
bjoernager/rust
1
Fork 0
Code Activity

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

Browse source 
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
Download patch file Download diff file Expand all files Collapse all files

35
compiler/rustc_borrowck/src/type_check/mod.rs
View file

@ -30,8 +30,9 @@ use rustc_middle::ty::cast::CastTy;
use rustc_middle::ty::subst::{GenericArgKind, SubstsRef, UserSubsts};
use rustc_middle::ty::visit::TypeVisitable;
use rustc_middle::ty::{
self, CanonicalUserTypeAnnotation, CanonicalUserTypeAnnotations, OpaqueHiddenType,
OpaqueTypeKey, RegionVid, ToPredicate, Ty, TyCtxt, UserType, UserTypeAnnotationIndex,
self, Binder, CanonicalUserTypeAnnotation, CanonicalUserTypeAnnotations, Dynamic,
OpaqueHiddenType, OpaqueTypeKey, RegionVid, ToPredicate, Ty, TyCtxt, UserType,
UserTypeAnnotationIndex,
};
use rustc_span::def_id::CRATE_DEF_ID;
use rustc_span::{Span, DUMMY_SP};
@ -2013,6 +2014,36 @@ impl<'a, 'tcx> TypeChecker<'a, 'tcx> {
);
}
CastKind::DynStar => {
// get the constraints from the target type (`dyn* Clone`)
//
// apply them to prove that the source type `Foo` implements `Clone` etc
let (existential_predicates, region) = match ty.kind() {
Dynamic(predicates, region, ty::DynStar) => (predicates, region),
_ => panic!("Invalid dyn* cast_ty"),
};
let self_ty = op.ty(body, tcx);
self.prove_predicates(
existential_predicates
.iter()
.map(|predicate| predicate.with_self_ty(tcx, self_ty)),
location.to_locations(),
ConstraintCategory::Cast,
);
let outlives_predicate =
tcx.mk_predicate(Binder::dummy(ty::PredicateKind::TypeOutlives(
ty::OutlivesPredicate(self_ty, *region),
)));
self.prove_predicate(
outlives_predicate,
location.to_locations(),
ConstraintCategory::Cast,
);
}
CastKind::Pointer(PointerCast::MutToConstPointer) => {
let ty::RawPtr(ty::TypeAndMut {
ty: ty_from,