bjoernager/rust
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Add ptr::Pointee trait (for all types) and ptr::metadata function

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RFC: https://github.com/rust-lang/rfcs/pull/2580
This commit is contained in:
Simon Sapin 2020-10-19 15:38:11 +02:00
parent 9503ea19ed
commit 696b239f72
17 changed files with 349 additions and 10 deletions
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68
compiler/rustc_trait_selection/src/traits/project.rs
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@ -12,7 +12,7 @@ use super::SelectionContext;
use super::SelectionError;
use super::{
ImplSourceClosureData, ImplSourceDiscriminantKindData, ImplSourceFnPointerData,
ImplSourceGeneratorData, ImplSourceUserDefinedData,
ImplSourceGeneratorData, ImplSourcePointeeData, ImplSourceUserDefinedData,
};
use super::{Normalized, NormalizedTy, ProjectionCacheEntry, ProjectionCacheKey};
@ -1069,6 +1069,51 @@ fn assemble_candidates_from_impls<'cx, 'tcx>(
| ty::Error(_) => false,
}
}
super::ImplSource::Pointee(..) => {
// While `Pointee` is automatically implemented for every type,
// the concrete metadata type may not be known yet.
//
// Any type with multiple potential metadata types is therefore not eligible.
let self_ty = selcx.infcx().shallow_resolve(obligation.predicate.self_ty());
// FIXME: should this normalize?
let tail = selcx.tcx().struct_tail_without_normalization(self_ty);
match tail.kind() {
ty::Bool
| ty::Char
| ty::Int(_)
| ty::Uint(_)
| ty::Float(_)
| ty::Foreign(_)
| ty::Str
| ty::Array(..)
| ty::Slice(_)
| ty::RawPtr(..)
| ty::Ref(..)
| ty::FnDef(..)
| ty::FnPtr(..)
| ty::Dynamic(..)
| ty::Closure(..)
| ty::Generator(..)
| ty::GeneratorWitness(..)
| ty::Never
// If returned by `struct_tail_without_normalization` this is a unit struct
// without any fields, or not a struct, and therefore is Sized.
| ty::Adt(..)
// If returned by `struct_tail_without_normalization` this is the empty tuple.
| ty::Tuple(..)
// Integers and floats are always Sized, and so have unit type metadata.
| ty::Infer(ty::InferTy::IntVar(_) | ty::InferTy::FloatVar(..)) => true,
ty::Projection(..)
| ty::Opaque(..)
| ty::Param(..)
| ty::Bound(..)
| ty::Placeholder(..)
| ty::Infer(..)
| ty::Error(_) => false,
}
}
super::ImplSource::Param(..) => {
// This case tell us nothing about the value of an
// associated type. Consider:
@ -1169,6 +1214,7 @@ fn confirm_select_candidate<'cx, 'tcx>(
super::ImplSource::DiscriminantKind(data) => {
confirm_discriminant_kind_candidate(selcx, obligation, data)
}
super::ImplSource::Pointee(data) => confirm_pointee_candidate(selcx, obligation, data),
super::ImplSource::Object(_)
| super::ImplSource::AutoImpl(..)
| super::ImplSource::Param(..)
@ -1256,6 +1302,26 @@ fn confirm_discriminant_kind_candidate<'cx, 'tcx>(
confirm_param_env_candidate(selcx, obligation, ty::Binder::dummy(predicate), false)
}
fn confirm_pointee_candidate<'cx, 'tcx>(
selcx: &mut SelectionContext<'cx, 'tcx>,
obligation: &ProjectionTyObligation<'tcx>,
_: ImplSourcePointeeData,
) -> Progress<'tcx> {
let tcx = selcx.tcx();
let self_ty = selcx.infcx().shallow_resolve(obligation.predicate.self_ty());
let substs = tcx.mk_substs([self_ty.into()].iter());
let metadata_def_id = tcx.require_lang_item(LangItem::Metadata, None);
let predicate = ty::ProjectionPredicate {
projection_ty: ty::ProjectionTy { substs, item_def_id: metadata_def_id },
ty: self_ty.ptr_metadata_ty(tcx),
};
confirm_param_env_candidate(selcx, obligation, ty::Binder::bind(predicate), false)
}
fn confirm_fn_pointer_candidate<'cx, 'tcx>(
selcx: &mut SelectionContext<'cx, 'tcx>,
obligation: &ProjectionTyObligation<'tcx>,