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Auto merge of #126161 - Bryanskiy:delegation-generics-4, r=petrochenkov

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Delegation: support generics in associated delegation items

This is a continuation of https://github.com/rust-lang/rust/pull/125929.

[design](https://github.com/Bryanskiy/posts/blob/master/delegation%20in%20generic%20contexts.md)

Generic parameters inheritance was implemented in all contexts. Generic arguments are not yet supported.

r? `@petrochenkov`
This commit is contained in:
bors 2024-09-07 18:12:05 +00:00
commit ec867f03bc
16 changed files with 778 additions and 446 deletions
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16
compiler/rustc_hir_analysis/src/collect/generics_of.rs
View File

@ -59,6 +59,12 @@ pub(super) fn generics_of(tcx: TyCtxt<'_>, def_id: LocalDefId) -> ty::Generics {
let hir_id = tcx.local_def_id_to_hir_id(def_id);
let node = tcx.hir_node(hir_id);
if let Some(sig) = node.fn_sig()
&& let Some(sig_id) = sig.decl.opt_delegation_sig_id()
{
return inherit_generics_for_delegation_item(tcx, def_id, sig_id);
}
let parent_def_id = match node {
Node::ImplItem(_)
| Node::TraitItem(_)
@ -229,16 +235,6 @@ pub(super) fn generics_of(tcx: TyCtxt<'_>, def_id: LocalDefId) -> ty::Generics {
// inherit the generics of the item.
Some(parent.to_def_id())
}
ItemKind::Fn(sig, _, _) => {
// For a delegation item inherit generics from callee.
if let Some(sig_id) = sig.decl.opt_delegation_sig_id()
&& let Some(generics) =
inherit_generics_for_delegation_item(tcx, def_id, sig_id)
{
return generics;
}
None
}
_ => None,
},
_ => None,

16
compiler/rustc_hir_analysis/src/collect/predicates_of.rs
View File

@ -138,6 +138,12 @@ fn gather_explicit_predicates_of(tcx: TyCtxt<'_>, def_id: LocalDefId) -> ty::Gen
let hir_id = tcx.local_def_id_to_hir_id(def_id);
let node = tcx.hir_node(hir_id);
if let Some(sig) = node.fn_sig()
&& let Some(sig_id) = sig.decl.opt_delegation_sig_id()
{
return inherit_predicates_for_delegation_item(tcx, def_id, sig_id);
}
let mut is_trait = None;
let mut is_default_impl_trait = None;
@ -164,16 +170,6 @@ fn gather_explicit_predicates_of(tcx: TyCtxt<'_>, def_id: LocalDefId) -> ty::Gen
ItemKind::Trait(_, _, _, self_bounds, ..) | ItemKind::TraitAlias(_, self_bounds) => {
is_trait = Some(self_bounds);
}
ItemKind::Fn(sig, _, _) => {
// For a delegation item inherit predicates from callee.
if let Some(sig_id) = sig.decl.opt_delegation_sig_id()
&& let Some(predicates) =
inherit_predicates_for_delegation_item(tcx, def_id, sig_id)
{
return predicates;
}
}
_ => {}
}
};

447
compiler/rustc_hir_analysis/src/delegation.rs
View File

@ -1,3 +1,7 @@
//! Support inheriting generic parameters and predicates for function delegation.
//!
//! For more information about delegation design, see the tracking issue #118212.
use std::assert_matches::debug_assert_matches;
use rustc_data_structures::fx::FxHashMap;
@ -5,7 +9,7 @@ use rustc_hir::def::DefKind;
use rustc_hir::def_id::{DefId, LocalDefId};
use rustc_middle::ty::fold::{TypeFoldable, TypeFolder, TypeSuperFoldable};
use rustc_middle::ty::{self, Ty, TyCtxt};
use rustc_span::ErrorGuaranteed;
use rustc_span::{ErrorGuaranteed, Span};
use rustc_type_ir::visit::TypeVisitableExt;
type RemapTable = FxHashMap<u32, u32>;
@ -76,127 +80,381 @@ fn fn_kind<'tcx>(tcx: TyCtxt<'tcx>, def_id: DefId) -> FnKind {
}
}
/// Given the current context(caller and callee `FnKind`), it specifies
/// the policy of predicates and generic parameters inheritance.
#[derive(Clone, Copy, Debug, PartialEq)]
enum InheritanceKind {
/// Copying all predicates and parameters, including those of the parent
/// container.
///
/// Boolean value defines whether the `Self` parameter or `Self: Trait`
/// predicate are copied. It's always equal to `false` except when
/// delegating from a free function to a trait method.
///
/// FIXME(fn_delegation): This often leads to type inference
/// errors. Support providing generic arguments or restrict use sites.
WithParent(bool),
/// The trait implementation should be compatible with the original trait.
/// Therefore, for trait implementations only the method's own parameters
/// and predicates are copied.
Own,
}
struct GenericsBuilder<'tcx> {
tcx: TyCtxt<'tcx>,
sig_id: DefId,
parent: Option<DefId>,
inh_kind: InheritanceKind,
}
impl<'tcx> GenericsBuilder<'tcx> {
fn new(tcx: TyCtxt<'tcx>, sig_id: DefId) -> GenericsBuilder<'tcx> {
GenericsBuilder { tcx, sig_id, parent: None, inh_kind: InheritanceKind::WithParent(false) }
}
fn with_parent(mut self, parent: DefId) -> Self {
self.parent = Some(parent);
self
}
fn with_inheritance_kind(mut self, inh_kind: InheritanceKind) -> Self {
self.inh_kind = inh_kind;
self
}
fn build(self) -> ty::Generics {
let mut own_params = vec![];
let sig_generics = self.tcx.generics_of(self.sig_id);
if let InheritanceKind::WithParent(has_self) = self.inh_kind
&& let Some(parent_def_id) = sig_generics.parent
{
let sig_parent_generics = self.tcx.generics_of(parent_def_id);
own_params.append(&mut sig_parent_generics.own_params.clone());
if !has_self {
own_params.remove(0);
}
}
own_params.append(&mut sig_generics.own_params.clone());
// Lifetime parameters must be declared before type and const parameters.
// Therefore, When delegating from a free function to a associated function,
// generic parameters need to be reordered:
//
// trait Trait<'a, A> {
// fn foo<'b, B>(...) {...}
// }
//
// reuse Trait::foo;
// desugaring:
// fn foo<'a, 'b, This: Trait<'a, A>, A, B>(...) {
// Trait::foo(...)
// }
own_params.sort_by_key(|key| key.kind.is_ty_or_const());
let param_def_id_to_index =
own_params.iter().map(|param| (param.def_id, param.index)).collect();
let (parent_count, has_self) = if let Some(def_id) = self.parent {
let parent_generics = self.tcx.generics_of(def_id);
let parent_kind = self.tcx.def_kind(def_id);
(parent_generics.count(), parent_kind == DefKind::Trait)
} else {
(0, false)
};
for (idx, param) in own_params.iter_mut().enumerate() {
param.index = (idx + parent_count) as u32;
// FIXME(fn_delegation): Default parameters are not inherited, because they are
// not permitted in functions. Therefore, there are 2 options here:
//
// - We can create non-default generic parameters.
// - We can substitute default parameters into the signature.
//
// At the moment, first option has been selected as the most general.
if let ty::GenericParamDefKind::Type { has_default, .. }
| ty::GenericParamDefKind::Const { has_default, .. } = &mut param.kind
{
*has_default = false;
}
}
ty::Generics {
parent: self.parent,
parent_count,
own_params,
param_def_id_to_index,
has_self,
has_late_bound_regions: sig_generics.has_late_bound_regions,
host_effect_index: sig_generics.host_effect_index,
}
}
}
struct PredicatesBuilder<'tcx> {
tcx: TyCtxt<'tcx>,
sig_id: DefId,
parent: Option<DefId>,
inh_kind: InheritanceKind,
args: ty::GenericArgsRef<'tcx>,
}
impl<'tcx> PredicatesBuilder<'tcx> {
fn new(
tcx: TyCtxt<'tcx>,
args: ty::GenericArgsRef<'tcx>,
sig_id: DefId,
) -> PredicatesBuilder<'tcx> {
PredicatesBuilder {
tcx,
sig_id,
parent: None,
inh_kind: InheritanceKind::WithParent(false),
args,
}
}
fn with_parent(mut self, parent: DefId) -> Self {
self.parent = Some(parent);
self
}
fn with_inheritance_kind(mut self, inh_kind: InheritanceKind) -> Self {
self.inh_kind = inh_kind;
self
}
fn build(self) -> ty::GenericPredicates<'tcx> {
struct PredicatesCollector<'tcx> {
tcx: TyCtxt<'tcx>,
preds: Vec<(ty::Clause<'tcx>, Span)>,
args: ty::GenericArgsRef<'tcx>,
}
impl<'tcx> PredicatesCollector<'tcx> {
fn new(tcx: TyCtxt<'tcx>, args: ty::GenericArgsRef<'tcx>) -> PredicatesCollector<'tcx> {
PredicatesCollector { tcx, preds: vec![], args }
}
fn with_own_preds(
mut self,
f: impl Fn(DefId) -> ty::GenericPredicates<'tcx>,
def_id: DefId,
) -> Self {
let preds = f(def_id).instantiate_own(self.tcx, self.args);
self.preds.extend(preds);
self
}
fn with_preds(
mut self,
f: impl Fn(DefId) -> ty::GenericPredicates<'tcx> + Copy,
def_id: DefId,
) -> Self {
let preds = f(def_id);
if let Some(parent_def_id) = preds.parent {
self = self.with_own_preds(f, parent_def_id);
}
self.with_own_preds(f, def_id)
}
}
let collector = PredicatesCollector::new(self.tcx, self.args);
// `explicit_predicates_of` is used here to avoid copying `Self: Trait` predicate.
// Note: `predicates_of` query can also add inferred outlives predicates, but that
// is not the case here as `sig_id` is either a trait or a function.
let preds = match self.inh_kind {
InheritanceKind::WithParent(false) => {
collector.with_preds(|def_id| self.tcx.explicit_predicates_of(def_id), self.sig_id)
}
InheritanceKind::WithParent(true) => {
collector.with_preds(|def_id| self.tcx.predicates_of(def_id), self.sig_id)
}
InheritanceKind::Own => {
collector.with_own_preds(|def_id| self.tcx.predicates_of(def_id), self.sig_id)
}
}
.preds;
ty::GenericPredicates {
parent: self.parent,
predicates: self.tcx.arena.alloc_from_iter(preds),
// FIXME(fn_delegation): Support effects.
effects_min_tys: ty::List::empty(),
}
}
}
struct GenericArgsBuilder<'tcx> {
tcx: TyCtxt<'tcx>,
remap_table: RemapTable,
sig_id: DefId,
def_id: LocalDefId,
}
impl<'tcx> GenericArgsBuilder<'tcx> {
fn new(tcx: TyCtxt<'tcx>, sig_id: DefId, def_id: LocalDefId) -> GenericArgsBuilder<'tcx> {
GenericArgsBuilder { tcx, remap_table: FxHashMap::default(), sig_id, def_id }
}
fn build_from_args(mut self, args: ty::GenericArgsRef<'tcx>) -> ty::GenericArgsRef<'tcx> {
let caller_generics = self.tcx.generics_of(self.def_id);
let callee_generics = self.tcx.generics_of(self.sig_id);
for caller_param in &caller_generics.own_params {
let callee_index =
callee_generics.param_def_id_to_index(self.tcx, caller_param.def_id).unwrap();
self.remap_table.insert(callee_index, caller_param.index);
}
let mut folder = ParamIndexRemapper { tcx: self.tcx, remap_table: self.remap_table };
args.fold_with(&mut folder)
}
}
fn create_generic_args<'tcx>(
tcx: TyCtxt<'tcx>,
def_id: LocalDefId,
sig_id: DefId,
) -> ty::GenericArgsRef<'tcx> {
let caller_generics = tcx.generics_of(def_id);
let callee_generics = tcx.generics_of(sig_id);
let builder = GenericArgsBuilder::new(tcx, sig_id, def_id);
let caller_kind = fn_kind(tcx, def_id.into());
let callee_kind = fn_kind(tcx, sig_id);
// FIXME(fn_delegation): Support generics on associated delegation items.
// Error will be reported in `check_constraints`.
match (caller_kind, callee_kind) {
(FnKind::Free, _) => {
// Lifetime parameters must be declared before type and const parameters.
// Therefore, When delegating from a free function to a associated function,
// generic parameters need to be reordered:
//
// trait Trait<'a, A> {
// fn foo<'b, B>(...) {...}
// }
//
// reuse Trait::foo;
// desugaring:
// fn foo<'a, 'b, This: Trait<'a, A>, A, B>(...) {
// Trait::foo(...)
// }
let mut remap_table = RemapTable::default();
for caller_param in &caller_generics.own_params {
let callee_index =
callee_generics.param_def_id_to_index(tcx, caller_param.def_id).unwrap();
remap_table.insert(callee_index, caller_param.index);
}
let mut folder = ParamIndexRemapper { tcx, remap_table };
ty::GenericArgs::identity_for_item(tcx, sig_id).fold_with(&mut folder)
(FnKind::Free, FnKind::Free)
| (FnKind::Free, FnKind::AssocTrait)
| (FnKind::AssocInherentImpl, FnKind::Free)
| (FnKind::AssocTrait, FnKind::Free)
| (FnKind::AssocTrait, FnKind::AssocTrait) => {
let args = ty::GenericArgs::identity_for_item(tcx, sig_id);
builder.build_from_args(args)
}
// FIXME(fn_delegation): Only `Self` param supported here.
(FnKind::AssocTraitImpl, FnKind::AssocTrait)
| (FnKind::AssocInherentImpl, FnKind::AssocTrait) => {
(FnKind::AssocTraitImpl, FnKind::AssocTrait) => {
let callee_generics = tcx.generics_of(sig_id);
let parent = tcx.parent(def_id.into());
let parent_args =
tcx.impl_trait_header(parent).unwrap().trait_ref.instantiate_identity().args;
let trait_args = ty::GenericArgs::identity_for_item(tcx, sig_id);
let method_args = tcx.mk_args_from_iter(trait_args.iter().skip(callee_generics.parent_count));
let method_args = builder.build_from_args(method_args);
tcx.mk_args_from_iter(parent_args.iter().chain(method_args))
}
(FnKind::AssocInherentImpl, FnKind::AssocTrait) => {
let parent = tcx.parent(def_id.into());
let self_ty = tcx.type_of(parent).instantiate_identity();
let generic_self_ty = ty::GenericArg::from(self_ty);
tcx.mk_args_from_iter(std::iter::once(generic_self_ty))
let trait_args = ty::GenericArgs::identity_for_item(tcx, sig_id);
let trait_args = builder.build_from_args(trait_args);
let args = std::iter::once(generic_self_ty).chain(trait_args.iter().skip(1));
tcx.mk_args_from_iter(args)
}
_ => ty::GenericArgs::identity_for_item(tcx, sig_id),
// For trait impl's `sig_id` is always equal to the corresponding trait method.
(FnKind::AssocTraitImpl, _)
| (_, FnKind::AssocTraitImpl)
// Delegation to inherent methods is not yet supported.
| (_, FnKind::AssocInherentImpl) => unreachable!(),
}
}
// FIXME(fn_delegation): Move generics inheritance to the AST->HIR lowering.
// For now, generic parameters are not propagated to the generated call,
// which leads to inference errors:
//
// fn foo<T>(x: i32) {}
//
// reuse foo as bar;
// desugaring:
// fn bar<T>() {
// foo::<_>() // ERROR: type annotations needed
// }
pub(crate) fn inherit_generics_for_delegation_item<'tcx>(
tcx: TyCtxt<'tcx>,
def_id: LocalDefId,
sig_id: DefId,
) -> Option<ty::Generics> {
// FIXME(fn_delegation): Support generics on associated delegation items.
// Error will be reported in `check_constraints`.
if fn_kind(tcx, def_id.into()) != FnKind::Free {
return None;
}
) -> ty::Generics {
let builder = GenericsBuilder::new(tcx, sig_id);
let mut own_params = vec![];
let caller_kind = fn_kind(tcx, def_id.into());
let callee_kind = fn_kind(tcx, sig_id);
match (caller_kind, callee_kind) {
(FnKind::Free, FnKind::Free)
| (FnKind::Free, FnKind::AssocTrait) => builder.with_inheritance_kind(InheritanceKind::WithParent(true)).build(),
let callee_generics = tcx.generics_of(sig_id);
if let Some(parent_sig_id) = callee_generics.parent {
let parent_sig_generics = tcx.generics_of(parent_sig_id);
own_params.append(&mut parent_sig_generics.own_params.clone());
}
own_params.append(&mut callee_generics.own_params.clone());
// Lifetimes go first.
own_params.sort_by_key(|key| key.kind.is_ty_or_const());
for (idx, param) in own_params.iter_mut().enumerate() {
param.index = idx as u32;
// Default parameters are not inherited: they are not allowed
// in fn's.
if let ty::GenericParamDefKind::Type { has_default, .. }
| ty::GenericParamDefKind::Const { has_default, .. } = &mut param.kind
{
*has_default = false;
(FnKind::AssocTraitImpl, FnKind::AssocTrait) => {
builder
.with_parent(tcx.parent(def_id.into()))
.with_inheritance_kind(InheritanceKind::Own)
.build()
}
(FnKind::AssocInherentImpl, FnKind::AssocTrait)
| (FnKind::AssocTrait, FnKind::AssocTrait) => {
builder
.with_parent(tcx.parent(def_id.into()))
.build()
}
(FnKind::AssocInherentImpl, FnKind::Free)
| (FnKind::AssocTrait, FnKind::Free) => {
builder
.with_parent(tcx.parent(def_id.into()))
.build()
}
// For trait impl's `sig_id` is always equal to the corresponding trait method.
(FnKind::AssocTraitImpl, _)
| (_, FnKind::AssocTraitImpl)
// Delegation to inherent methods is not yet supported.
| (_, FnKind::AssocInherentImpl) => unreachable!(),
}
let param_def_id_to_index =
own_params.iter().map(|param| (param.def_id, param.index)).collect();
Some(ty::Generics {
parent: None,
parent_count: 0,
own_params,
param_def_id_to_index,
has_self: false,
has_late_bound_regions: callee_generics.has_late_bound_regions,
host_effect_index: callee_generics.host_effect_index,
})
}
pub(crate) fn inherit_predicates_for_delegation_item<'tcx>(
tcx: TyCtxt<'tcx>,
def_id: LocalDefId,
sig_id: DefId,
) -> Option<ty::GenericPredicates<'tcx>> {
// FIXME(fn_delegation): Support generics on associated delegation items.
// Error will be reported in `check_constraints`.
if fn_kind(tcx, def_id.into()) != FnKind::Free {
return None;
}
let callee_predicates = tcx.predicates_of(sig_id);
) -> ty::GenericPredicates<'tcx> {
let args = create_generic_args(tcx, def_id, sig_id);
let builder = PredicatesBuilder::new(tcx, args, sig_id);
let mut preds = vec![];
if let Some(parent_id) = callee_predicates.parent {
preds.extend(tcx.predicates_of(parent_id).instantiate_own(tcx, args));
let caller_kind = fn_kind(tcx, def_id.into());
let callee_kind = fn_kind(tcx, sig_id);
match (caller_kind, callee_kind) {
(FnKind::Free, FnKind::Free)
| (FnKind::Free, FnKind::AssocTrait) => {
builder.with_inheritance_kind(InheritanceKind::WithParent(true)).build()
}
(FnKind::AssocTraitImpl, FnKind::AssocTrait) => {
builder
.with_parent(tcx.parent(def_id.into()))
.with_inheritance_kind(InheritanceKind::Own)
.build()
}
(FnKind::AssocInherentImpl, FnKind::AssocTrait)
| (FnKind::AssocTrait, FnKind::AssocTrait)
| (FnKind::AssocInherentImpl, FnKind::Free)
| (FnKind::AssocTrait, FnKind::Free) => {
builder
.with_parent(tcx.parent(def_id.into()))
.build()
}
// For trait impl's `sig_id` is always equal to the corresponding trait method.
(FnKind::AssocTraitImpl, _)
| (_, FnKind::AssocTraitImpl)
// Delegation to inherent methods is not yet supported.
| (_, FnKind::AssocInherentImpl) => unreachable!(),
}
preds.extend(callee_predicates.instantiate_own(tcx, args));
Some(ty::GenericPredicates {
parent: None,
predicates: tcx.arena.alloc_from_iter(preds),
effects_min_tys: ty::List::empty(),
})
}
fn check_constraints<'tcx>(
@ -224,19 +482,6 @@ fn check_constraints<'tcx>(
emit("recursive delegation is not supported yet");
}
if fn_kind(tcx, def_id.into()) != FnKind::Free {
let sig_generics = tcx.generics_of(sig_id);
let parent = tcx.parent(def_id.into());
let parent_generics = tcx.generics_of(parent);
let parent_has_self = parent_generics.has_self as usize;
let sig_has_self = sig_generics.has_self as usize;
if sig_generics.count() > sig_has_self || parent_generics.count() > parent_has_self {
emit("early bound generics are not supported for associated delegation items");
}
}
ret
}

3
compiler/rustc_trait_selection/src/error_reporting/infer/need_type_info.rs
View File

@ -1296,6 +1296,9 @@ impl<'a, 'tcx> Visitor<'tcx> for FindInferSourceVisitor<'a, 'tcx> {
&& let Some(def_id) = self.typeck_results.type_dependent_def_id(expr.hir_id)
&& self.tecx.tcx.trait_of_item(def_id).is_some()
&& !has_impl_trait(def_id)
// FIXME(fn_delegation): In delegation item argument spans are equal to last path
// segment. This leads to ICE's when emitting `multipart_suggestion`.
&& tcx.hir().opt_delegation_sig_id(expr.hir_id.owner.def_id).is_none()
{
let successor =
method_args.get(0).map_or_else(|| (")", span.hi()), |arg| (", ", arg.span.lo()));

29
tests/ui/delegation/generics/impl-to-free-fn-pass.rs Normal file
View File

@ -0,0 +1,29 @@
//@ run-pass
#![feature(fn_delegation)]
#![allow(incomplete_features)]
mod to_reuse {
pub fn foo<T, U>(_: T, y: U) -> U { y }
}
trait Trait<T> {
fn foo(&self, x: T) -> T { x }
}
struct F;
impl<T> Trait<T> for F {}
struct S<T>(F, T);
impl<T, U> Trait<T> for S<U> {
reuse to_reuse::foo { &self.0 }
}
impl<T> S<T> {
reuse to_reuse::foo;
}
fn main() {
let s = S(F, 42);
assert_eq!(S::<i32>::foo(F, 1), 1);
assert_eq!(<S<_> as Trait<_>>::foo(&s, 1), 1);
}

44
tests/ui/delegation/generics/impl-to-trait-method.rs Normal file
View File

@ -0,0 +1,44 @@
#![feature(fn_delegation)]
#![allow(incomplete_features)]
mod bounds {
trait Trait0 {}
trait Trait1<T> {
fn foo<U>(&self)
where
T: Trait0,
U: Trait0,
Self: Trait0,
//~^ ERROR the trait bound `bounds::S: Trait0` is not satisfied
{
}
}
struct F;
impl<T> Trait1<T> for F {}
struct S(F);
impl<T> Trait1<T> for S {
reuse Trait1::<T>::foo { &self.0 }
//~^ ERROR the trait bound `bounds::F: Trait0` is not satisfied
}
}
mod unconstrained_parameter {
trait Trait<T> {
fn foo(&self) {}
}
struct F;
impl<T> Trait<T> for F {}
struct S(F);
impl S {
reuse Trait::foo { &self.0 }
//~^ ERROR type annotations needed
}
}
fn main() {}

49
tests/ui/delegation/generics/impl-to-trait-method.stderr Normal file
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@ -0,0 +1,49 @@
error[E0277]: the trait bound `bounds::S: Trait0` is not satisfied
--> $DIR/impl-to-trait-method.rs:12:19
|
LL | Self: Trait0,
| ^^^^^^ the trait `Trait0` is not implemented for `bounds::S`
|
help: this trait has no implementations, consider adding one
--> $DIR/impl-to-trait-method.rs:5:5
|
LL | trait Trait0 {}
| ^^^^^^^^^^^^
= help: see issue #48214
help: add `#![feature(trivial_bounds)]` to the crate attributes to enable
|
LL + #![feature(trivial_bounds)]
|
error[E0277]: the trait bound `bounds::F: Trait0` is not satisfied
--> $DIR/impl-to-trait-method.rs:24:34
|
LL | reuse Trait1::<T>::foo { &self.0 }
| --- ^^^^^^^ the trait `Trait0` is not implemented for `bounds::F`
| |
| required by a bound introduced by this call
|
help: this trait has no implementations, consider adding one
--> $DIR/impl-to-trait-method.rs:5:5
|
LL | trait Trait0 {}
| ^^^^^^^^^^^^
note: required by a bound in `Trait1::foo`
--> $DIR/impl-to-trait-method.rs:12:19
|
LL | fn foo<U>(&self)
| --- required by a bound in this associated function
...
LL | Self: Trait0,
| ^^^^^^ required by this bound in `Trait1::foo`
error[E0282]: type annotations needed
--> $DIR/impl-to-trait-method.rs:39:22
|
LL | reuse Trait::foo { &self.0 }
| ^^^ cannot infer type for type parameter `T` declared on the trait `Trait`
error: aborting due to 3 previous errors
Some errors have detailed explanations: E0277, E0282.
For more information about an error, try `rustc --explain E0277`.

77
tests/ui/delegation/generics/impl-trait-to-trait-method-pass.rs Normal file
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@ -0,0 +1,77 @@
//@ run-pass
#![feature(fn_delegation)]
#![allow(incomplete_features)]
use std::iter::{Iterator, Map};
pub mod same_trait {
use super::*;
pub struct MapOuter<I, F> {
pub inner: Map<I, F>
}
impl<B, I: Iterator, F> Iterator for MapOuter<I, F>
where
F: FnMut(I::Item) -> B,
{
type Item = <Map<I, F> as Iterator>::Item;
reuse Iterator::{next, fold} { self.inner }
}
}
use same_trait::MapOuter;
mod another_trait {
use super::*;
trait ZipImpl<A, B> {
type Item;
fn next(&mut self) -> Option<Self::Item>;
}
pub struct Zip<A, B> {
pub a: A,
pub b: B,
}
impl<A: Iterator, B: Iterator> ZipImpl<A, B> for Zip<A, B> {
type Item = (A::Item, B::Item);
fn next(&mut self) -> Option<(A::Item, B::Item)> {
let x = self.a.next()?;
let y = self.b.next()?;
Some((x, y))
}
}
impl<A: Iterator, B: Iterator> Iterator for Zip<A, B> {
type Item = (A::Item, B::Item);
// Parameters are inherited from `Iterator::next`, not from `ZipImpl::next`.
// Otherwise, there would be a compilation error due to an unconstrained parameter.
reuse ZipImpl::next;
}
}
use another_trait::Zip;
fn main() {
{
let x = vec![1, 2, 3];
let iter = x.iter().map(|val| val * 2);
let outer_iter = MapOuter { inner: iter };
let val = outer_iter.fold(0, |acc, x| acc + x);
assert_eq!(val, 12);
}
{
let x = vec![1, 2];
let y = vec![4, 5];
let mut zip = Zip { a: x.iter(), b: y.iter() };
assert_eq!(zip.next(), Some((&1, &4)));
assert_eq!(zip.next(), Some((&2, &5)));
}
}

23
tests/ui/delegation/generics/inherent-impl-to-trait-method-pass.rs Normal file
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@ -0,0 +1,23 @@
//@ run-pass
#![feature(fn_delegation)]
#![allow(incomplete_features)]
trait Trait<T> {
fn foo<U>(&self, x: T, y: U) -> (T, U) {
(x, y)
}
}
impl<T> Trait<T> for () {}
struct S<T>(T, ());
impl<T> S<T> {
reuse Trait::foo { self.1 }
}
fn main() {
let s = S((), ());
assert_eq!(s.foo(1u32, 2i32), (1u32, 2i32));
}

30
tests/ui/delegation/generics/trait-method-to-other-pass.rs Normal file
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@ -0,0 +1,30 @@
//@ run-pass
#![feature(fn_delegation)]
#![allow(incomplete_features)]
mod to_reuse {
pub fn foo<T>(x: T) -> T { x }
}
trait Trait1<T, U> {
fn foo(&self, _: T, x: U) -> U { x }
}
#[derive(Default)]
struct F;
impl<T, U> Trait1<T, U> for F {}
trait Trait2<T> {
fn get_f(&self) -> &F { &F }
reuse Trait1::foo as bar { self.get_f() }
reuse to_reuse::foo as baz;
}
impl Trait2<u64> for F {}
fn main() {
assert_eq!(F.bar(1u8, 2u16), 2u16);
assert_eq!(F::baz(1u8), 1u8);
}

4
tests/ui/delegation/ice-issue-124347.rs
View File

@ -1,12 +1,12 @@
#![feature(fn_delegation)]
#![allow(incomplete_features)]
// FIXME(fn_delegation): `recursive delegation` error should be emitted here
trait Trait {
reuse Trait::foo { &self.0 }
//~^ ERROR recursive delegation is not supported yet
//~^ ERROR cycle detected when computing generics of `Trait::foo`
}
// FIXME(fn_delegation): `recursive delegation` error should be emitted here
reuse foo;
//~^ ERROR cycle detected when computing generics of `foo`

14
tests/ui/delegation/ice-issue-124347.stderr
View File

@ -1,8 +1,16 @@
error: recursive delegation is not supported yet
--> $DIR/ice-issue-124347.rs:5:18
error[E0391]: cycle detected when computing generics of `Trait::foo`
--> $DIR/ice-issue-124347.rs:6:18
|
LL | reuse Trait::foo { &self.0 }
| ^^^ callee defined here
| ^^^
|
= note: ...which immediately requires computing generics of `Trait::foo` again
note: cycle used when inheriting delegation signature
--> $DIR/ice-issue-124347.rs:6:18
|
LL | reuse Trait::foo { &self.0 }
| ^^^
= note: see https://rustc-dev-guide.rust-lang.org/overview.html#queries and https://rustc-dev-guide.rust-lang.org/query.html for more information
error[E0391]: cycle detected when computing generics of `foo`
--> $DIR/ice-issue-124347.rs:10:7

116
tests/ui/delegation/not-supported.rs
View File

@ -1,116 +0,0 @@
#![feature(const_trait_impl)]
#![feature(c_variadic)]
#![feature(effects)]
#![feature(fn_delegation)]
#![allow(incomplete_features)]
mod generics {
trait GenericTrait<T> {
fn bar(&self, x: T) -> T { x }
fn bar1() {}
}
trait Trait {
fn foo(&self, x: i32) -> i32 { x }
fn foo1<'a>(&self, x: &'a i32) -> &'a i32 { x }
fn foo2<T>(&self, x: T) -> T { x }
fn foo3<'a: 'a>(_: &'a u32) {}
reuse GenericTrait::bar;
//~^ ERROR early bound generics are not supported for associated delegation items
reuse GenericTrait::bar1;
//~^ ERROR early bound generics are not supported for associated delegation items
}
struct F;
impl Trait for F {}
impl<T> GenericTrait<T> for F {}
struct S(F);
impl<T> GenericTrait<T> for S {
reuse <F as GenericTrait<T>>::bar { &self.0 }
//~^ ERROR early bound generics are not supported for associated delegation items
reuse GenericTrait::<T>::bar1;
//~^ ERROR early bound generics are not supported for associated delegation items
}
impl GenericTrait<()> for () {
reuse GenericTrait::bar { &F }
//~^ ERROR early bound generics are not supported for associated delegation items
reuse GenericTrait::bar1;
//~^ ERROR early bound generics are not supported for associated delegation items
}
impl Trait for &S {
reuse Trait::foo;
//~^ ERROR early bound generics are not supported for associated delegation items
}
impl Trait for S {
reuse Trait::foo1 { &self.0 }
reuse Trait::foo2 { &self.0 }
//~^ ERROR early bound generics are not supported for associated delegation items
//~| ERROR method `foo2` has 0 type parameters but its trait declaration has 1 type parameter
reuse <F as Trait>::foo3;
//~^ ERROR early bound generics are not supported for associated delegation items
//~| ERROR lifetime parameters or bounds on associated function `foo3` do not match the trait declaration
}
struct GenericS<T>(T);
impl<T> Trait for GenericS<T> {
reuse Trait::foo { &self.0 }
//~^ ERROR early bound generics are not supported for associated delegation items
}
}
mod opaque {
trait Trait {}
impl Trait for () {}
mod to_reuse {
use super::Trait;
pub fn opaque_ret() -> impl Trait { unimplemented!() }
//~^ warn: this function depends on never type fallback being `()`
//~| warn: this was previously accepted by the compiler but is being phased out; it will become a hard error in a future release!
}
trait ToReuse {
fn opaque_ret() -> impl Trait { unimplemented!() }
//~^ warn: this function depends on never type fallback being `()`
//~| warn: this was previously accepted by the compiler but is being phased out; it will become a hard error in a future release!
}
// FIXME: Inherited `impl Trait`s create query cycles when used inside trait impls.
impl ToReuse for u8 {
reuse to_reuse::opaque_ret; //~ ERROR cycle detected when computing type
}
impl ToReuse for u16 {
reuse ToReuse::opaque_ret; //~ ERROR cycle detected when computing type
}
}
mod recursive {
mod to_reuse1 {
pub mod to_reuse2 {
pub fn foo() {}
}
pub reuse to_reuse2::foo;
}
reuse to_reuse1::foo;
//~^ ERROR recursive delegation is not supported yet
}
mod effects {
#[const_trait]
trait Trait {
fn foo();
}
reuse Trait::foo;
//~^ ERROR delegation to a function with effect parameter is not supported yet
}
fn main() {}

204
tests/ui/delegation/not-supported.stderr
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@ -1,204 +0,0 @@
error: using `#![feature(effects)]` without enabling next trait solver globally
|
= note: the next trait solver must be enabled globally for the effects feature to work correctly
= help: use `-Znext-solver` to enable
error: early bound generics are not supported for associated delegation items
--> $DIR/not-supported.rs:18:29
|
LL | fn bar(&self, x: T) -> T { x }
| ------------------------ callee defined here
...
LL | reuse GenericTrait::bar;
| ^^^
error: early bound generics are not supported for associated delegation items
--> $DIR/not-supported.rs:20:29
|
LL | fn bar1() {}
| --------- callee defined here
...
LL | reuse GenericTrait::bar1;
| ^^^^
error: early bound generics are not supported for associated delegation items
--> $DIR/not-supported.rs:31:39
|
LL | fn bar(&self, x: T) -> T { x }
| ------------------------ callee defined here
...
LL | reuse <F as GenericTrait<T>>::bar { &self.0 }
| ^^^
error: early bound generics are not supported for associated delegation items
--> $DIR/not-supported.rs:33:34
|
LL | fn bar1() {}
| --------- callee defined here
...
LL | reuse GenericTrait::<T>::bar1;
| ^^^^
error: early bound generics are not supported for associated delegation items
--> $DIR/not-supported.rs:38:29
|
LL | fn bar(&self, x: T) -> T { x }
| ------------------------ callee defined here
...
LL | reuse GenericTrait::bar { &F }
| ^^^
error: early bound generics are not supported for associated delegation items
--> $DIR/not-supported.rs:40:29
|
LL | fn bar1() {}
| --------- callee defined here
...
LL | reuse GenericTrait::bar1;
| ^^^^
error: early bound generics are not supported for associated delegation items
--> $DIR/not-supported.rs:45:22
|
LL | fn foo(&self, x: i32) -> i32 { x }
| ---------------------------- callee defined here
...
LL | reuse Trait::foo;
| ^^^
error[E0049]: method `foo2` has 0 type parameters but its trait declaration has 1 type parameter
--> $DIR/not-supported.rs:51:22
|
LL | fn foo2<T>(&self, x: T) -> T { x }
| - expected 1 type parameter
...
LL | reuse Trait::foo2 { &self.0 }
| ^^^^ found 0 type parameters
error: early bound generics are not supported for associated delegation items
--> $DIR/not-supported.rs:54:29
|
LL | fn foo3<'a: 'a>(_: &'a u32) {}
| --------------------------- callee defined here
...
LL | reuse <F as Trait>::foo3;
| ^^^^
error[E0195]: lifetime parameters or bounds on associated function `foo3` do not match the trait declaration
--> $DIR/not-supported.rs:54:29
|
LL | fn foo3<'a: 'a>(_: &'a u32) {}
| -------- lifetimes in impl do not match this associated function in trait
...
LL | reuse <F as Trait>::foo3;
| ^^^^ lifetimes do not match associated function in trait
error: delegation to a function with effect parameter is not supported yet
--> $DIR/not-supported.rs:112:18
|
LL | fn foo();
| --------- callee defined here
...
LL | reuse Trait::foo;
| ^^^
error: early bound generics are not supported for associated delegation items
--> $DIR/not-supported.rs:61:22
|
LL | fn foo(&self, x: i32) -> i32 { x }
| ---------------------------- callee defined here
...
LL | reuse Trait::foo { &self.0 }
| ^^^
error: early bound generics are not supported for associated delegation items
--> $DIR/not-supported.rs:51:22
|
LL | fn foo2<T>(&self, x: T) -> T { x }
| ---------------------------- callee defined here
...
LL | reuse Trait::foo2 { &self.0 }
| ^^^^
warning: this function depends on never type fallback being `()`
--> $DIR/not-supported.rs:79:9
|
LL | fn opaque_ret() -> impl Trait { unimplemented!() }
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
|
= warning: this was previously accepted by the compiler but is being phased out; it will become a hard error in a future release!
= note: for more information, see issue #123748 <https://github.com/rust-lang/rust/issues/123748>
= help: specify the types explicitly
note: in edition 2024, the requirement `!: opaque::Trait` will fail
--> $DIR/not-supported.rs:79:28
|
LL | fn opaque_ret() -> impl Trait { unimplemented!() }
| ^^^^^^^^^^
= note: `#[warn(dependency_on_unit_never_type_fallback)]` on by default
error[E0391]: cycle detected when computing type of `opaque::<impl at $DIR/not-supported.rs:85:5: 85:24>::{synthetic#0}`
--> $DIR/not-supported.rs:86:25
|
LL | reuse to_reuse::opaque_ret;
| ^^^^^^^^^^
|
note: ...which requires comparing an impl and trait method signature, inferring any hidden `impl Trait` types in the process...
--> $DIR/not-supported.rs:86:25
|
LL | reuse to_reuse::opaque_ret;
| ^^^^^^^^^^
= note: ...which again requires computing type of `opaque::<impl at $DIR/not-supported.rs:85:5: 85:24>::{synthetic#0}`, completing the cycle
note: cycle used when checking that `opaque::<impl at $DIR/not-supported.rs:85:5: 85:24>` is well-formed
--> $DIR/not-supported.rs:85:5
|
LL | impl ToReuse for u8 {
| ^^^^^^^^^^^^^^^^^^^
= note: see https://rustc-dev-guide.rust-lang.org/overview.html#queries and https://rustc-dev-guide.rust-lang.org/query.html for more information
warning: this function depends on never type fallback being `()`
--> $DIR/not-supported.rs:73:9
|
LL | pub fn opaque_ret() -> impl Trait { unimplemented!() }
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
|
= warning: this was previously accepted by the compiler but is being phased out; it will become a hard error in a future release!
= note: for more information, see issue #123748 <https://github.com/rust-lang/rust/issues/123748>
= help: specify the types explicitly
note: in edition 2024, the requirement `!: opaque::Trait` will fail
--> $DIR/not-supported.rs:73:32
|
LL | pub fn opaque_ret() -> impl Trait { unimplemented!() }
| ^^^^^^^^^^
error[E0391]: cycle detected when computing type of `opaque::<impl at $DIR/not-supported.rs:88:5: 88:25>::{synthetic#0}`
--> $DIR/not-supported.rs:89:24
|
LL | reuse ToReuse::opaque_ret;
| ^^^^^^^^^^
|
note: ...which requires comparing an impl and trait method signature, inferring any hidden `impl Trait` types in the process...
--> $DIR/not-supported.rs:89:24
|
LL | reuse ToReuse::opaque_ret;
| ^^^^^^^^^^
= note: ...which again requires computing type of `opaque::<impl at $DIR/not-supported.rs:88:5: 88:25>::{synthetic#0}`, completing the cycle
note: cycle used when checking that `opaque::<impl at $DIR/not-supported.rs:88:5: 88:25>` is well-formed
--> $DIR/not-supported.rs:88:5
|
LL | impl ToReuse for u16 {
| ^^^^^^^^^^^^^^^^^^^^
= note: see https://rustc-dev-guide.rust-lang.org/overview.html#queries and https://rustc-dev-guide.rust-lang.org/query.html for more information
error: recursive delegation is not supported yet
--> $DIR/not-supported.rs:102:22
|
LL | pub reuse to_reuse2::foo;
| --- callee defined here
...
LL | reuse to_reuse1::foo;
| ^^^
error: aborting due to 17 previous errors; 2 warnings emitted
Some errors have detailed explanations: E0049, E0195, E0391.
For more information about an error, try `rustc --explain E0049`.

57
tests/ui/delegation/unsupported.rs Normal file
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@ -0,0 +1,57 @@
#![feature(const_trait_impl)]
#![feature(c_variadic)]
#![feature(effects)]
#![feature(fn_delegation)]
#![allow(incomplete_features)]
mod opaque {
trait Trait {}
impl Trait for () {}
mod to_reuse {
use super::Trait;
pub fn opaque_ret() -> impl Trait { unimplemented!() }
//~^ warn: this function depends on never type fallback being `()`
//~| warn: this was previously accepted by the compiler but is being phased out; it will become a hard error in a future release!
}
trait ToReuse {
fn opaque_ret() -> impl Trait { unimplemented!() }
//~^ warn: this function depends on never type fallback being `()`
//~| warn: this was previously accepted by the compiler but is being phased out; it will become a hard error in a future release!
}
// FIXME: Inherited `impl Trait`s create query cycles when used inside trait impls.
impl ToReuse for u8 {
reuse to_reuse::opaque_ret; //~ ERROR cycle detected when computing type
}
impl ToReuse for u16 {
reuse ToReuse::opaque_ret; //~ ERROR cycle detected when computing type
}
}
mod recursive {
mod to_reuse1 {
pub mod to_reuse2 {
pub fn foo() {}
}
pub reuse to_reuse2::foo;
}
reuse to_reuse1::foo;
//~^ ERROR recursive delegation is not supported yet
}
mod effects {
#[const_trait]
trait Trait {
fn foo();
}
reuse Trait::foo;
//~^ ERROR delegation to a function with effect parameter is not supported yet
}
fn main() {}

95
tests/ui/delegation/unsupported.stderr Normal file
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@ -0,0 +1,95 @@
error: using `#![feature(effects)]` without enabling next trait solver globally
|
= note: the next trait solver must be enabled globally for the effects feature to work correctly
= help: use `-Znext-solver` to enable
warning: this function depends on never type fallback being `()`
--> $DIR/unsupported.rs:20:9
|
LL | fn opaque_ret() -> impl Trait { unimplemented!() }
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
|
= warning: this was previously accepted by the compiler but is being phased out; it will become a hard error in a future release!
= note: for more information, see issue #123748 <https://github.com/rust-lang/rust/issues/123748>
= help: specify the types explicitly
note: in edition 2024, the requirement `!: opaque::Trait` will fail
--> $DIR/unsupported.rs:20:28
|
LL | fn opaque_ret() -> impl Trait { unimplemented!() }
| ^^^^^^^^^^
= note: `#[warn(dependency_on_unit_never_type_fallback)]` on by default
error[E0391]: cycle detected when computing type of `opaque::<impl at $DIR/unsupported.rs:26:5: 26:24>::{synthetic#0}`
--> $DIR/unsupported.rs:27:25
|
LL | reuse to_reuse::opaque_ret;
| ^^^^^^^^^^
|
note: ...which requires comparing an impl and trait method signature, inferring any hidden `impl Trait` types in the process...
--> $DIR/unsupported.rs:27:25
|
LL | reuse to_reuse::opaque_ret;
| ^^^^^^^^^^
= note: ...which again requires computing type of `opaque::<impl at $DIR/unsupported.rs:26:5: 26:24>::{synthetic#0}`, completing the cycle
note: cycle used when checking that `opaque::<impl at $DIR/unsupported.rs:26:5: 26:24>` is well-formed
--> $DIR/unsupported.rs:26:5
|
LL | impl ToReuse for u8 {
| ^^^^^^^^^^^^^^^^^^^
= note: see https://rustc-dev-guide.rust-lang.org/overview.html#queries and https://rustc-dev-guide.rust-lang.org/query.html for more information
warning: this function depends on never type fallback being `()`
--> $DIR/unsupported.rs:14:9
|
LL | pub fn opaque_ret() -> impl Trait { unimplemented!() }
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
|
= warning: this was previously accepted by the compiler but is being phased out; it will become a hard error in a future release!
= note: for more information, see issue #123748 <https://github.com/rust-lang/rust/issues/123748>
= help: specify the types explicitly
note: in edition 2024, the requirement `!: opaque::Trait` will fail
--> $DIR/unsupported.rs:14:32
|
LL | pub fn opaque_ret() -> impl Trait { unimplemented!() }
| ^^^^^^^^^^
error[E0391]: cycle detected when computing type of `opaque::<impl at $DIR/unsupported.rs:29:5: 29:25>::{synthetic#0}`
--> $DIR/unsupported.rs:30:24
|
LL | reuse ToReuse::opaque_ret;
| ^^^^^^^^^^
|
note: ...which requires comparing an impl and trait method signature, inferring any hidden `impl Trait` types in the process...
--> $DIR/unsupported.rs:30:24
|
LL | reuse ToReuse::opaque_ret;
| ^^^^^^^^^^
= note: ...which again requires computing type of `opaque::<impl at $DIR/unsupported.rs:29:5: 29:25>::{synthetic#0}`, completing the cycle
note: cycle used when checking that `opaque::<impl at $DIR/unsupported.rs:29:5: 29:25>` is well-formed
--> $DIR/unsupported.rs:29:5
|
LL | impl ToReuse for u16 {
| ^^^^^^^^^^^^^^^^^^^^
= note: see https://rustc-dev-guide.rust-lang.org/overview.html#queries and https://rustc-dev-guide.rust-lang.org/query.html for more information
error: recursive delegation is not supported yet
--> $DIR/unsupported.rs:43:22
|
LL | pub reuse to_reuse2::foo;
| --- callee defined here
...
LL | reuse to_reuse1::foo;
| ^^^
error: delegation to a function with effect parameter is not supported yet
--> $DIR/unsupported.rs:53:18
|
LL | fn foo();
| --------- callee defined here
...
LL | reuse Trait::foo;
| ^^^
error: aborting due to 5 previous errors; 2 warnings emitted
For more information about this error, try `rustc --explain E0391`.