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builtin impl confirmation wuhu #114409

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Aug 4, 2023
Merged

builtin impl confirmation wuhu #114409

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40 changes: 17 additions & 23 deletions compiler/rustc_trait_selection/src/traits/select/confirmation.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -987,9 +987,7 @@ impl<'cx, 'tcx> SelectionContext<'cx, 'tcx> {
let target = self.infcx.shallow_resolve(target);
debug!(?source, ?target, "confirm_builtin_unsize_candidate");

let mut nested = vec![];
let src;
match (source.kind(), target.kind()) {
Ok(match (source.kind(), target.kind()) {
// Trait+Kx+'a -> Trait+Ky+'b (auto traits and lifetime subtyping).
(&ty::Dynamic(ref data_a, r_a, dyn_a), &ty::Dynamic(ref data_b, r_b, dyn_b))
if dyn_a == dyn_b =>
Expand All @@ -1016,24 +1014,23 @@ impl<'cx, 'tcx> SelectionContext<'cx, 'tcx> {

// Require that the traits involved in this upcast are **equal**;
// only the **lifetime bound** is changed.
let InferOk { obligations, .. } = self
let InferOk { mut obligations, .. } = self
.infcx
.at(&obligation.cause, obligation.param_env)
.sup(DefineOpaqueTypes::No, target, source_trait)
.map_err(|_| Unimplemented)?;
nested.extend(obligations);

// Register one obligation for 'a: 'b.
let outlives = ty::OutlivesPredicate(r_a, r_b);
nested.push(Obligation::with_depth(
obligations.push(Obligation::with_depth(
tcx,
obligation.cause.clone(),
obligation.recursion_depth + 1,
obligation.param_env,
obligation.predicate.rebind(outlives),
));

src = BuiltinImplSource::Misc;
ImplSource::Builtin(BuiltinImplSource::Misc, obligations)
}

// `T` -> `Trait`
Expand All @@ -1059,11 +1056,10 @@ impl<'cx, 'tcx> SelectionContext<'cx, 'tcx> {
// words, if the object type is `Foo + Send`, this would create an obligation for
// the `Send` check.)
// - Projection predicates
nested.extend(
data.iter().map(|predicate| {
predicate_to_obligation(predicate.with_self_ty(tcx, source))
}),
);
let mut nested: Vec<_> = data
.iter()
.map(|predicate| predicate_to_obligation(predicate.with_self_ty(tcx, source)))
.collect();

// We can only make objects from sized types.
let tr = ty::TraitRef::from_lang_item(
Expand All @@ -1081,7 +1077,7 @@ impl<'cx, 'tcx> SelectionContext<'cx, 'tcx> {
ty::Binder::dummy(ty::ClauseKind::TypeOutlives(outlives)).to_predicate(tcx),
));

src = BuiltinImplSource::Misc;
ImplSource::Builtin(BuiltinImplSource::Misc, nested)
}

// `[T; n]` -> `[T]`
Expand All @@ -1091,9 +1087,8 @@ impl<'cx, 'tcx> SelectionContext<'cx, 'tcx> {
.at(&obligation.cause, obligation.param_env)
.eq(DefineOpaqueTypes::No, b, a)
.map_err(|_| Unimplemented)?;
nested.extend(obligations);

src = BuiltinImplSource::Misc;
ImplSource::Builtin(BuiltinImplSource::Misc, obligations)
}

// `Struct<T>` -> `Struct<U>`
Expand All @@ -1106,6 +1101,8 @@ impl<'cx, 'tcx> SelectionContext<'cx, 'tcx> {
let tail_field = def.non_enum_variant().tail();
let tail_field_ty = tcx.type_of(tail_field.did);

let mut nested = vec![];

// Extract `TailField<T>` and `TailField<U>` from `Struct<T>` and `Struct<U>`,
// normalizing in the process, since `type_of` returns something directly from
// astconv (which means it's un-normalized).
Expand Down Expand Up @@ -1151,7 +1148,7 @@ impl<'cx, 'tcx> SelectionContext<'cx, 'tcx> {
);
nested.push(tail_unsize_obligation);

src = BuiltinImplSource::Misc;
ImplSource::Builtin(BuiltinImplSource::Misc, nested)
}

// `(.., T)` -> `(.., U)`
Expand All @@ -1166,27 +1163,24 @@ impl<'cx, 'tcx> SelectionContext<'cx, 'tcx> {
// last element is equal to the target.
let new_tuple =
Ty::new_tup_from_iter(tcx, a_mid.iter().copied().chain(iter::once(b_last)));
let InferOk { obligations, .. } = self
let InferOk { mut obligations, .. } = self
.infcx
.at(&obligation.cause, obligation.param_env)
.eq(DefineOpaqueTypes::No, target, new_tuple)
.map_err(|_| Unimplemented)?;
nested.extend(obligations);

// Add a nested `T: Unsize<U>` predicate.
let last_unsize_obligation = obligation.with(
tcx,
ty::TraitRef::new(tcx, obligation.predicate.def_id(), [a_last, b_last]),
);
nested.push(last_unsize_obligation);
obligations.push(last_unsize_obligation);

src = BuiltinImplSource::TupleUnsizing;
ImplSource::Builtin(BuiltinImplSource::TupleUnsizing, obligations)
}

_ => bug!("source: {source}, target: {target}"),
};

Ok(ImplSource::Builtin(src, nested))
})
}

fn confirm_const_destruct_candidate(
Expand Down
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