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Consolidate opaque ty and async fn lowering code

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This commit is contained in:
Michael Goulet 2023-08-04 22:16:29 +00:00
parent fbc11e9690
commit 57a96893f6
5 changed files with 191 additions and 429 deletions
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603
compiler/rustc_ast_lowering/src/lib.rs
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@ -512,11 +512,6 @@ impl<'a, 'hir> LoweringContext<'a, 'hir> {
self.resolver.node_id_to_def_id.get(&node).map(|local_def_id| *local_def_id) self.resolver.node_id_to_def_id.get(&node).map(|local_def_id| *local_def_id)
} }
fn orig_local_def_id(&self, node: NodeId) -> LocalDefId {
self.orig_opt_local_def_id(node)
.unwrap_or_else(|| panic!("no entry for node id: `{node:?}`"))
}
/// Given the id of some node in the AST, finds the `LocalDefId` associated with it by the name /// Given the id of some node in the AST, finds the `LocalDefId` associated with it by the name
/// resolver (if any), after applying any remapping from `get_remapped_def_id`. /// resolver (if any), after applying any remapping from `get_remapped_def_id`.
/// ///
@ -1521,6 +1516,45 @@ impl<'a, 'hir> LoweringContext<'a, 'hir> {
// frequently opened issues show. // frequently opened issues show.
let opaque_ty_span = self.mark_span_with_reason(DesugaringKind::OpaqueTy, span, None); let opaque_ty_span = self.mark_span_with_reason(DesugaringKind::OpaqueTy, span, None);
let captured_lifetimes_to_duplicate = match origin {
hir::OpaqueTyOrigin::TyAlias { .. } => {
// in a TAIT like `type Foo<'a> = impl Foo<'a>`, we don't duplicate any
// lifetimes, since we don't have the issue that any are late-bound.
Vec::new()
}
hir::OpaqueTyOrigin::FnReturn(..) => {
// in fn return position, like the `fn test<'a>() -> impl Debug + 'a`
// example, we only need to duplicate lifetimes that appear in the
// bounds, since those are the only ones that are captured by the opaque.
lifetime_collector::lifetimes_in_bounds(&self.resolver, bounds)
}
hir::OpaqueTyOrigin::AsyncFn(..) => {
unreachable!("should be using `lower_async_fn_ret_ty`")
}
};
debug!(?captured_lifetimes_to_duplicate);
self.lower_opaque_inner(
opaque_ty_node_id,
origin,
in_trait,
captured_lifetimes_to_duplicate,
span,
opaque_ty_span,
|this| this.lower_param_bounds(bounds, itctx),
)
}
fn lower_opaque_inner(
&mut self,
opaque_ty_node_id: NodeId,
origin: hir::OpaqueTyOrigin,
in_trait: bool,
captured_lifetimes_to_duplicate: Vec<Lifetime>,
span: Span,
opaque_ty_span: Span,
lower_item_bounds: impl FnOnce(&mut Self) -> &'hir [hir::GenericBound<'hir>],
) -> hir::TyKind<'hir> {
let opaque_ty_def_id = self.create_def( let opaque_ty_def_id = self.create_def(
self.current_hir_id_owner.def_id, self.current_hir_id_owner.def_id,
opaque_ty_node_id, opaque_ty_node_id,
@ -1529,201 +1563,39 @@ impl<'a, 'hir> LoweringContext<'a, 'hir> {
); );
debug!(?opaque_ty_def_id); debug!(?opaque_ty_def_id);
// If this came from a TAIT (as opposed to a function that returns an RPIT), we only want // Map from captured (old) lifetime to synthetic (new) lifetime.
// to capture the lifetimes that appear in the bounds. So visit the bounds to find out // Used to resolve lifetimes in the bounds of the opaque.
// exactly which ones those are. let mut captured_to_synthesized_mapping = FxHashMap::default();
let lifetimes_to_remap = match origin { // List of (early-bound) synthetic lifetimes that are owned by the opaque.
hir::OpaqueTyOrigin::TyAlias { .. } => { // This is used to create the `hir::Generics` owned by the opaque.
// in a TAIT like `type Foo<'a> = impl Foo<'a>`, we don't keep all the lifetime parameters let mut synthesized_lifetime_definitions = vec![];
Vec::new() // Pairs of lifetime arg (that resolves to the captured lifetime)
} // and the def-id of the (early-bound) synthetic lifetime definition.
hir::OpaqueTyOrigin::AsyncFn(..) | hir::OpaqueTyOrigin::FnReturn(..) => { // This is used both to create generics for the `TyKind::OpaqueDef` that
// in fn return position, like the `fn test<'a>() -> impl Debug + 'a` example, // we return, and also as a captured lifetime mapping for RPITITs.
// we only keep the lifetimes that appear in the `impl Debug` itself: let mut synthesized_lifetime_args = vec![];
lifetime_collector::lifetimes_in_bounds(&self.resolver, bounds)
}
};
debug!(?lifetimes_to_remap);
let mut new_remapping = FxHashMap::default(); for lifetime in captured_lifetimes_to_duplicate {
// Contains the new lifetime definitions created for the TAIT (if any).
// If this opaque type is only capturing a subset of the lifetimes (those that appear in
// bounds), then create the new lifetime parameters required and create a mapping from the
// old `'a` (on the function) to the new `'a` (on the opaque type).
let collected_lifetimes =
self.create_lifetime_defs(opaque_ty_def_id, &lifetimes_to_remap, &mut new_remapping);
debug!(?collected_lifetimes);
debug!(?new_remapping);
// This creates HIR lifetime arguments as `hir::GenericArg`, in the given example `type
// TestReturn<'a, T, 'x> = impl Debug + 'x`, it creates a collection containing `&['x]`.
let collected_lifetime_mapping: Vec<_> = collected_lifetimes
.iter()
.map(|(node_id, lifetime)| {
let id = self.next_node_id();
let lifetime = self.new_named_lifetime(lifetime.id, id, lifetime.ident);
let def_id = self.local_def_id(*node_id);
(lifetime, def_id)
})
.collect();
debug!(?collected_lifetime_mapping);
self.with_hir_id_owner(opaque_ty_node_id, |lctx| {
// Install the remapping from old to new (if any):
lctx.with_remapping(new_remapping, |lctx| {
// This creates HIR lifetime definitions as `hir::GenericParam`, in the given
// example `type TestReturn<'a, T, 'x> = impl Debug + 'x`, it creates a collection
// containing `&['x]`.
let lifetime_defs = lctx.arena.alloc_from_iter(collected_lifetimes.iter().map(
|&(new_node_id, lifetime)| {
let hir_id = lctx.lower_node_id(new_node_id);
debug_assert_ne!(lctx.opt_local_def_id(new_node_id), None);
let (name, kind) = if lifetime.ident.name == kw::UnderscoreLifetime {
(hir::ParamName::Fresh, hir::LifetimeParamKind::Elided)
} else {
(
hir::ParamName::Plain(lifetime.ident),
hir::LifetimeParamKind::Explicit,
)
};
hir::GenericParam {
hir_id,
def_id: lctx.local_def_id(new_node_id),
name,
span: lifetime.ident.span,
pure_wrt_drop: false,
kind: hir::GenericParamKind::Lifetime { kind },
colon_span: None,
source: hir::GenericParamSource::Generics,
}
},
));
debug!(?lifetime_defs);
// Then when we lower the param bounds, references to 'a are remapped to 'a1, so we
// get back Debug + 'a1, which is suitable for use on the TAIT.
let hir_bounds = lctx.lower_param_bounds(bounds, itctx);
debug!(?hir_bounds);
let lifetime_mapping = if in_trait {
Some(
&*self.arena.alloc_from_iter(
collected_lifetime_mapping
.iter()
.map(|(lifetime, def_id)| (**lifetime, *def_id)),
),
)
} else {
None
};
let opaque_ty_item = hir::OpaqueTy {
generics: self.arena.alloc(hir::Generics {
params: lifetime_defs,
predicates: &[],
has_where_clause_predicates: false,
where_clause_span: lctx.lower_span(span),
span: lctx.lower_span(span),
}),
bounds: hir_bounds,
origin,
lifetime_mapping,
in_trait,
};
debug!(?opaque_ty_item);
lctx.generate_opaque_type(opaque_ty_def_id, opaque_ty_item, span, opaque_ty_span)
})
});
// `impl Trait` now just becomes `Foo<'a, 'b, ..>`.
hir::TyKind::OpaqueDef(
hir::ItemId { owner_id: hir::OwnerId { def_id: opaque_ty_def_id } },
self.arena.alloc_from_iter(
collected_lifetime_mapping
.iter()
.map(|(lifetime, _)| hir::GenericArg::Lifetime(*lifetime)),
),
in_trait,
)
}
/// Registers a new opaque type with the proper `NodeId`s and
/// returns the lowered node-ID for the opaque type.
fn generate_opaque_type(
&mut self,
opaque_ty_id: LocalDefId,
opaque_ty_item: hir::OpaqueTy<'hir>,
span: Span,
opaque_ty_span: Span,
) -> hir::OwnerNode<'hir> {
let opaque_ty_item_kind = hir::ItemKind::OpaqueTy(self.arena.alloc(opaque_ty_item));
// Generate an `type Foo = impl Trait;` declaration.
trace!("registering opaque type with id {:#?}", opaque_ty_id);
let opaque_ty_item = hir::Item {
owner_id: hir::OwnerId { def_id: opaque_ty_id },
ident: Ident::empty(),
kind: opaque_ty_item_kind,
vis_span: self.lower_span(span.shrink_to_lo()),
span: self.lower_span(opaque_ty_span),
};
hir::OwnerNode::Item(self.arena.alloc(opaque_ty_item))
}
/// Given a `parent_def_id`, a list of `lifetimes_in_bounds` and a `remapping` hash to be
/// filled, this function creates new definitions for `Param` and `Fresh` lifetimes, inserts the
/// new definition, adds it to the remapping with the definition of the given lifetime and
/// returns a list of lifetimes to be lowered afterwards.
fn create_lifetime_defs(
&mut self,
parent_def_id: LocalDefId,
lifetimes_in_bounds: &[Lifetime],
remapping: &mut FxHashMap<LocalDefId, LocalDefId>,
) -> Vec<(NodeId, Lifetime)> {
let mut result = Vec::new();
for lifetime in lifetimes_in_bounds {
let res = self.resolver.get_lifetime_res(lifetime.id).unwrap_or(LifetimeRes::Error); let res = self.resolver.get_lifetime_res(lifetime.id).unwrap_or(LifetimeRes::Error);
debug!(?res); let old_def_id = match res {
LifetimeRes::Param { param: old_def_id, binder: _ } => old_def_id,
match res {
LifetimeRes::Param { param: old_def_id, binder: _ } => {
if remapping.get(&old_def_id).is_none() {
let node_id = self.next_node_id();
let new_def_id = self.create_def(
parent_def_id,
node_id,
DefPathData::LifetimeNs(lifetime.ident.name),
lifetime.ident.span,
);
remapping.insert(old_def_id, new_def_id);
result.push((node_id, *lifetime));
}
}
LifetimeRes::Fresh { param, binder: _ } => { LifetimeRes::Fresh { param, binder: _ } => {
debug_assert_eq!(lifetime.ident.name, kw::UnderscoreLifetime); debug_assert_eq!(lifetime.ident.name, kw::UnderscoreLifetime);
if let Some(old_def_id) = self.orig_opt_local_def_id(param) && remapping.get(&old_def_id).is_none() { if let Some(old_def_id) = self.orig_opt_local_def_id(param) {
let node_id = self.next_node_id(); old_def_id
} else {
let new_def_id = self.create_def( self.tcx
parent_def_id, .sess
node_id, .delay_span_bug(lifetime.ident.span, "no def-id for fresh lifetime");
DefPathData::LifetimeNs(kw::UnderscoreLifetime), continue;
lifetime.ident.span,
);
remapping.insert(old_def_id, new_def_id);
result.push((node_id, *lifetime));
} }
} }
LifetimeRes::Static | LifetimeRes::Error => {} // Opaques do not capture `'static`
LifetimeRes::Static | LifetimeRes::Error => {
continue;
}
res => { res => {
let bug_msg = format!( let bug_msg = format!(
@ -1732,10 +1604,113 @@ impl<'a, 'hir> LoweringContext<'a, 'hir> {
); );
span_bug!(lifetime.ident.span, "{}", bug_msg); span_bug!(lifetime.ident.span, "{}", bug_msg);
} }
};
if captured_to_synthesized_mapping.get(&old_def_id).is_none() {
// Create a new lifetime parameter local to the opaque.
let duplicated_lifetime_node_id = self.next_node_id();
let duplicated_lifetime_def_id = self.create_def(
opaque_ty_def_id,
duplicated_lifetime_node_id,
DefPathData::LifetimeNs(lifetime.ident.name),
lifetime.ident.span,
);
captured_to_synthesized_mapping.insert(old_def_id, duplicated_lifetime_def_id);
// FIXME: Instead of doing this, we could move this whole loop
// into the `with_hir_id_owner`, then just directly construct
// the `hir::GenericParam` here.
synthesized_lifetime_definitions.push((
duplicated_lifetime_node_id,
duplicated_lifetime_def_id,
lifetime.ident,
));
// Now make an arg that we can use for the substs of the opaque tykind.
let id = self.next_node_id();
let lifetime_arg = self.new_named_lifetime_with_res(id, lifetime.ident, res);
let duplicated_lifetime_def_id = self.local_def_id(duplicated_lifetime_node_id);
synthesized_lifetime_args.push((lifetime_arg, duplicated_lifetime_def_id))
} }
} }
result self.with_hir_id_owner(opaque_ty_node_id, |this| {
// Install the remapping from old to new (if any). This makes sure that
// any lifetimes that would have resolved to the def-id of captured
// lifetimes are remapped to the new *synthetic* lifetimes of the opaque.
let bounds = this
.with_remapping(captured_to_synthesized_mapping, |this| lower_item_bounds(this));
let generic_params = this.arena.alloc_from_iter(
synthesized_lifetime_definitions.iter().map(|&(new_node_id, new_def_id, ident)| {
let hir_id = this.lower_node_id(new_node_id);
let (name, kind) = if ident.name == kw::UnderscoreLifetime {
(hir::ParamName::Fresh, hir::LifetimeParamKind::Elided)
} else {
(hir::ParamName::Plain(ident), hir::LifetimeParamKind::Explicit)
};
hir::GenericParam {
hir_id,
def_id: new_def_id,
name,
span: ident.span,
pure_wrt_drop: false,
kind: hir::GenericParamKind::Lifetime { kind },
colon_span: None,
source: hir::GenericParamSource::Generics,
}
}),
);
debug!("lower_async_fn_ret_ty: generic_params={:#?}", generic_params);
let lifetime_mapping = if in_trait {
Some(&*self.arena.alloc_slice(&synthesized_lifetime_args))
} else {
None
};
let opaque_ty_item = hir::OpaqueTy {
generics: this.arena.alloc(hir::Generics {
params: generic_params,
predicates: &[],
has_where_clause_predicates: false,
where_clause_span: this.lower_span(span),
span: this.lower_span(span),
}),
bounds,
origin,
lifetime_mapping,
in_trait,
};
// Generate an `type Foo = impl Trait;` declaration.
trace!("registering opaque type with id {:#?}", opaque_ty_def_id);
let opaque_ty_item = hir::Item {
owner_id: hir::OwnerId { def_id: opaque_ty_def_id },
ident: Ident::empty(),
kind: hir::ItemKind::OpaqueTy(this.arena.alloc(opaque_ty_item)),
vis_span: this.lower_span(span.shrink_to_lo()),
span: this.lower_span(opaque_ty_span),
};
hir::OwnerNode::Item(this.arena.alloc(opaque_ty_item))
});
let generic_args = self.arena.alloc_from_iter(
synthesized_lifetime_args
.iter()
.map(|(lifetime, _)| hir::GenericArg::Lifetime(*lifetime)),
);
// Create the `Foo<...>` reference itself. Note that the `type
// Foo = impl Trait` is, internally, created as a child of the
// async fn, so the *type parameters* are inherited. It's
// only the lifetime parameters that we must supply.
hir::TyKind::OpaqueDef(
hir::ItemId { owner_id: hir::OwnerId { def_id: opaque_ty_def_id } },
generic_args,
in_trait,
)
} }
fn lower_fn_params_to_names(&mut self, decl: &FnDecl) -> &'hir [Ident] { fn lower_fn_params_to_names(&mut self, decl: &FnDecl) -> &'hir [Ident] {
@ -1813,9 +1788,10 @@ impl<'a, 'hir> LoweringContext<'a, 'hir> {
} }
} }
let fn_def_id = self.local_def_id(fn_node_id);
self.lower_async_fn_ret_ty( self.lower_async_fn_ret_ty(
&decl.output, &decl.output,
fn_node_id, fn_def_id,
ret_id, ret_id,
matches!(kind, FnDeclKind::Trait), matches!(kind, FnDeclKind::Trait),
) )
@ -1892,151 +1868,28 @@ impl<'a, 'hir> LoweringContext<'a, 'hir> {
fn lower_async_fn_ret_ty( fn lower_async_fn_ret_ty(
&mut self, &mut self,
output: &FnRetTy, output: &FnRetTy,
fn_node_id: NodeId, fn_def_id: LocalDefId,
opaque_ty_node_id: NodeId, opaque_ty_node_id: NodeId,
in_trait: bool, in_trait: bool,
) -> hir::FnRetTy<'hir> { ) -> hir::FnRetTy<'hir> {
let span = output.span(); let span = self.lower_span(output.span());
let opaque_ty_span = self.mark_span_with_reason(DesugaringKind::Async, span, None); let opaque_ty_span = self.mark_span_with_reason(DesugaringKind::Async, span, None);
let fn_def_id = self.local_def_id(fn_node_id); let captured_lifetimes: Vec<_> = self
.resolver
let opaque_ty_def_id = .take_extra_lifetime_params(opaque_ty_node_id)
self.create_def(fn_def_id, opaque_ty_node_id, DefPathData::ImplTrait, opaque_ty_span);
// When we create the opaque type for this async fn, it is going to have
// to capture all the lifetimes involved in the signature (including in the
// return type). This is done by introducing lifetime parameters for:
//
// - all the explicitly declared lifetimes from the impl and function itself;
// - all the elided lifetimes in the fn arguments;
// - all the elided lifetimes in the return type.
//
// So for example in this snippet:
//
// ```rust
// impl<'a> Foo<'a> {
// async fn bar<'b>(&self, x: &'b Vec<f64>, y: &str) -> &u32 {
// // ^ '0 ^ '1 ^ '2
// // elided lifetimes used below
// }
// }
// ```
//
// we would create an opaque type like:
//
// ```
// type Bar<'a, 'b, '0, '1, '2> = impl Future<Output = &'2 u32>;
// ```
//
// and we would then desugar `bar` to the equivalent of:
//
// ```rust
// impl<'a> Foo<'a> {
// fn bar<'b, '0, '1>(&'0 self, x: &'b Vec<f64>, y: &'1 str) -> Bar<'a, 'b, '0, '1, '_>
// }
// ```
//
// Note that the final parameter to `Bar` is `'_`, not `'2` --
// this is because the elided lifetimes from the return type
// should be figured out using the ordinary elision rules, and
// this desugaring achieves that.
// Calculate all the lifetimes that should be captured
// by the opaque type. This should include all in-scope
// lifetime parameters, including those defined in-band.
// Contains the new lifetime definitions created for the TAIT (if any) generated for the
// return type.
let mut collected_lifetimes = Vec::new();
let mut new_remapping = FxHashMap::default();
let extra_lifetime_params = self.resolver.take_extra_lifetime_params(opaque_ty_node_id);
debug!(?extra_lifetime_params);
for (ident, outer_node_id, outer_res) in extra_lifetime_params {
let outer_def_id = self.orig_local_def_id(outer_node_id);
let inner_node_id = self.next_node_id();
// Add a definition for the in scope lifetime def.
let inner_def_id = self.create_def(
opaque_ty_def_id,
inner_node_id,
DefPathData::LifetimeNs(ident.name),
ident.span,
);
new_remapping.insert(outer_def_id, inner_def_id);
let inner_res = match outer_res {
// Input lifetime like `'a`:
LifetimeRes::Param { param, .. } => {
LifetimeRes::Param { param, binder: fn_node_id }
}
// Input lifetime like `'1`:
LifetimeRes::Fresh { param, .. } => {
LifetimeRes::Fresh { param, binder: fn_node_id }
}
LifetimeRes::Static | LifetimeRes::Error => continue,
res => {
panic!(
"Unexpected lifetime resolution {:?} for {:?} at {:?}",
res, ident, ident.span
)
}
};
let lifetime = Lifetime { id: outer_node_id, ident };
collected_lifetimes.push((inner_node_id, lifetime, Some(inner_res)));
}
debug!(?collected_lifetimes);
// We only want to capture the lifetimes that appear in the bounds. So visit the bounds to
// find out exactly which ones those are.
// in fn return position, like the `fn test<'a>() -> impl Debug + 'a` example,
// we only keep the lifetimes that appear in the `impl Debug` itself:
let lifetimes_to_remap = lifetime_collector::lifetimes_in_ret_ty(&self.resolver, output);
debug!(?lifetimes_to_remap);
// If this opaque type is only capturing a subset of the lifetimes (those that appear in
// bounds), then create the new lifetime parameters required and create a mapping from the
// old `'a` (on the function) to the new `'a` (on the opaque type).
collected_lifetimes.extend(
self.create_lifetime_defs(opaque_ty_def_id, &lifetimes_to_remap, &mut new_remapping)
.into_iter() .into_iter()
.map(|(new_node_id, lifetime)| (new_node_id, lifetime, None)), .map(|(ident, id, _)| Lifetime { id, ident })
);
debug!(?collected_lifetimes);
debug!(?new_remapping);
// This creates pairs of HIR lifetimes and def_ids. In the given example `type
// TestReturn<'a, T, 'x> = impl Debug + 'x`, it creates a collection containing the
// new lifetime of the RPIT 'x and the def_id of the lifetime 'x corresponding to
// `TestReturn`.
let collected_lifetime_mapping: Vec<_> = collected_lifetimes
.iter()
.map(|(node_id, lifetime, res)| {
let id = self.next_node_id();
let res = res.unwrap_or(
self.resolver.get_lifetime_res(lifetime.id).unwrap_or(LifetimeRes::Error),
);
let lifetime = self.new_named_lifetime_with_res(id, lifetime.ident, res);
let def_id = self.local_def_id(*node_id);
(lifetime, def_id)
})
.collect(); .collect();
debug!(?collected_lifetime_mapping);
self.with_hir_id_owner(opaque_ty_node_id, |this| { let opaque_ty_ref = self.lower_opaque_inner(
// Install the remapping from old to new (if any): opaque_ty_node_id,
this.with_remapping(new_remapping, |this| { hir::OpaqueTyOrigin::AsyncFn(fn_def_id),
// We have to be careful to get elision right here. The in_trait,
// idea is that we create a lifetime parameter for each captured_lifetimes,
// lifetime in the return type. So, given a return type span,
// like `async fn foo(..) -> &[&u32]`, we lower to `impl opaque_ty_span,
// Future<Output = &'1 [ &'2 u32 ]>`. |this| {
//
// Then, we will create `fn foo(..) -> Foo<'_, '_>`, and
// hence the elision takes place at the fn site.
let future_bound = this.lower_async_fn_output_type_to_future_bound( let future_bound = this.lower_async_fn_output_type_to_future_bound(
output, output,
span, span,
@ -2052,96 +1905,10 @@ impl<'a, 'hir> LoweringContext<'a, 'hir> {
} }
}, },
); );
arena_vec![this; future_bound]
let generic_params = this.arena.alloc_from_iter(collected_lifetimes.iter().map(
|&(new_node_id, lifetime, _)| {
let hir_id = this.lower_node_id(new_node_id);
debug_assert_ne!(this.opt_local_def_id(new_node_id), None);
let (name, kind) = if lifetime.ident.name == kw::UnderscoreLifetime {
(hir::ParamName::Fresh, hir::LifetimeParamKind::Elided)
} else {
(
hir::ParamName::Plain(lifetime.ident),
hir::LifetimeParamKind::Explicit,
)
};
hir::GenericParam {
hir_id,
def_id: this.local_def_id(new_node_id),
name,
span: lifetime.ident.span,
pure_wrt_drop: false,
kind: hir::GenericParamKind::Lifetime { kind },
colon_span: None,
source: hir::GenericParamSource::Generics,
}
}, },
));
debug!("lower_async_fn_ret_ty: generic_params={:#?}", generic_params);
let lifetime_mapping = if in_trait {
Some(
&*self.arena.alloc_from_iter(
collected_lifetime_mapping
.iter()
.map(|(lifetime, def_id)| (**lifetime, *def_id)),
),
)
} else {
None
};
let opaque_ty_item = hir::OpaqueTy {
generics: this.arena.alloc(hir::Generics {
params: generic_params,
predicates: &[],
has_where_clause_predicates: false,
where_clause_span: this.lower_span(span),
span: this.lower_span(span),
}),
bounds: arena_vec![this; future_bound],
origin: hir::OpaqueTyOrigin::AsyncFn(fn_def_id),
lifetime_mapping,
in_trait,
};
trace!("exist ty from async fn def id: {:#?}", opaque_ty_def_id);
this.generate_opaque_type(opaque_ty_def_id, opaque_ty_item, span, opaque_ty_span)
})
});
// As documented above, we need to create the lifetime
// arguments to our opaque type. Continuing with our example,
// we're creating the type arguments for the return type:
//
// ```
// Bar<'a, 'b, '0, '1, '_>
// ```
//
// For the "input" lifetime parameters, we wish to create
// references to the parameters themselves, including the
// "implicit" ones created from parameter types (`'a`, `'b`,
// '`0`, `'1`).
//
// For the "output" lifetime parameters, we just want to
// generate `'_`.
let generic_args = self.arena.alloc_from_iter(
collected_lifetime_mapping
.iter()
.map(|(lifetime, _)| hir::GenericArg::Lifetime(*lifetime)),
); );
// Create the `Foo<...>` reference itself. Note that the `type
// Foo = impl Trait` is, internally, created as a child of the
// async fn, so the *type parameters* are inherited. It's
// only the lifetime parameters that we must supply.
let opaque_ty_ref = hir::TyKind::OpaqueDef(
hir::ItemId { owner_id: hir::OwnerId { def_id: opaque_ty_def_id } },
generic_args,
in_trait,
);
let opaque_ty = self.ty(opaque_ty_span, opaque_ty_ref); let opaque_ty = self.ty(opaque_ty_span, opaque_ty_ref);
hir::FnRetTy::Return(self.arena.alloc(opaque_ty)) hir::FnRetTy::Return(self.arena.alloc(opaque_ty))
} }

8
compiler/rustc_ast_lowering/src/lifetime_collector.rs
View file

@ -1,6 +1,6 @@
use super::ResolverAstLoweringExt; use super::ResolverAstLoweringExt;
use rustc_ast::visit::{self, BoundKind, LifetimeCtxt, Visitor}; use rustc_ast::visit::{self, BoundKind, LifetimeCtxt, Visitor};
use rustc_ast::{FnRetTy, GenericBounds, Lifetime, NodeId, PathSegment, PolyTraitRef, Ty, TyKind}; use rustc_ast::{GenericBounds, Lifetime, NodeId, PathSegment, PolyTraitRef, Ty, TyKind};
use rustc_hir::def::LifetimeRes; use rustc_hir::def::LifetimeRes;
use rustc_middle::span_bug; use rustc_middle::span_bug;
use rustc_middle::ty::ResolverAstLowering; use rustc_middle::ty::ResolverAstLowering;
@ -94,12 +94,6 @@ impl<'ast> Visitor<'ast> for LifetimeCollectVisitor<'ast> {
} }
} }
pub fn lifetimes_in_ret_ty(resolver: &ResolverAstLowering, ret_ty: &FnRetTy) -> Vec<Lifetime> {
let mut visitor = LifetimeCollectVisitor::new(resolver);
visitor.visit_fn_ret_ty(ret_ty);
visitor.collected_lifetimes
}
pub fn lifetimes_in_bounds( pub fn lifetimes_in_bounds(
resolver: &ResolverAstLowering, resolver: &ResolverAstLowering,
bounds: &GenericBounds, bounds: &GenericBounds,

2
compiler/rustc_hir/src/hir.rs
View file

@ -2675,7 +2675,7 @@ pub struct OpaqueTy<'hir> {
/// ///
/// This mapping associated a captured lifetime (first parameter) with the new /// This mapping associated a captured lifetime (first parameter) with the new
/// early-bound lifetime that was generated for the opaque. /// early-bound lifetime that was generated for the opaque.
pub lifetime_mapping: Option<&'hir [(Lifetime, LocalDefId)]>, pub lifetime_mapping: Option<&'hir [(&'hir Lifetime, LocalDefId)]>,
/// Whether the opaque is a return-position impl trait (or async future) /// Whether the opaque is a return-position impl trait (or async future)
/// originating from a trait method. This makes it so that the opaque is /// originating from a trait method. This makes it so that the opaque is
/// lowered as an associated type. /// lowered as an associated type.

2
compiler/rustc_hir_analysis/src/collect/predicates_of.rs
View file

@ -82,7 +82,7 @@ fn gather_explicit_predicates_of(tcx: TyCtxt<'_>, def_id: LocalDefId) -> ty::Gen
tcx, tcx,
def_id, def_id,
lifetime_mapping.iter().map(|(lifetime, def_id)| { lifetime_mapping.iter().map(|(lifetime, def_id)| {
(*lifetime, (*def_id, lifetime.ident.name, lifetime.ident.span)) (**lifetime, (*def_id, lifetime.ident.name, lifetime.ident.span))
}), }),
tcx.generics_of(def_id.to_def_id()), tcx.generics_of(def_id.to_def_id()),
&mut predicates, &mut predicates,

1
compiler/rustc_resolve/src/late.rs
View file

@ -1694,6 +1694,7 @@ impl<'a: 'ast, 'b, 'ast, 'tcx> LateResolutionVisitor<'a, 'b, 'ast, 'tcx> {
// Leave the responsibility to create the `LocalDefId` to lowering. // Leave the responsibility to create the `LocalDefId` to lowering.
let param = self.r.next_node_id(); let param = self.r.next_node_id();
let res = LifetimeRes::Fresh { param, binder }; let res = LifetimeRes::Fresh { param, binder };
self.record_lifetime_param(param, res);
// Record the created lifetime parameter so lowering can pick it up and add it to HIR. // Record the created lifetime parameter so lowering can pick it up and add it to HIR.
self.r self.r