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Auto merge of #90204 - cjgillot:owner-pull, r=michaelwoerister
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Make lowering pull-based

~Based on #90451
Part of #88186

The current lowering code visits all the item-likes in the AST in order, and lowers them one by one.
This PR changes it to index the AST and then proceed to lowering on-demand. This is closer to the logic of query-based lowering.
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@bors
bors committed Mar 31, 2022
2 parents 0331491 + 6b099db commit bd1a869
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Showing 5 changed files with 273 additions and 250 deletions.
248 changes: 132 additions & 116 deletions compiler/rustc_ast_lowering/src/item.rs
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Original file line number Diff line number Diff line change
@@ -1,16 +1,19 @@
use super::{AnonymousLifetimeMode, LoweringContext, ParamMode};
use super::{ImplTraitContext, ImplTraitPosition};
use super::{AstOwner, ImplTraitContext, ImplTraitPosition, ResolverAstLowering};
use crate::{Arena, FnDeclKind};

use rustc_ast::ptr::P;
use rustc_ast::visit::{self, AssocCtxt, FnCtxt, FnKind, Visitor};
use rustc_ast::visit::AssocCtxt;
use rustc_ast::*;
use rustc_data_structures::fx::FxHashSet;
use rustc_data_structures::fx::{FxHashMap, FxHashSet};
use rustc_data_structures::sorted_map::SortedMap;
use rustc_errors::struct_span_err;
use rustc_hir as hir;
use rustc_hir::def::{DefKind, Res};
use rustc_hir::def_id::LocalDefId;
use rustc_index::vec::Idx;
use rustc_hir::def_id::{LocalDefId, CRATE_DEF_ID};
use rustc_index::vec::{Idx, IndexVec};
use rustc_session::utils::NtToTokenstream;
use rustc_session::Session;
use rustc_span::source_map::{respan, DesugaringKind};
use rustc_span::symbol::{kw, sym, Ident};
use rustc_span::Span;
Expand All @@ -19,10 +22,14 @@ use smallvec::{smallvec, SmallVec};
use tracing::debug;

use std::iter;
use std::mem;

pub(super) struct ItemLowerer<'a, 'lowering, 'hir> {
pub(super) lctx: &'a mut LoweringContext<'lowering, 'hir>,
pub(super) struct ItemLowerer<'a, 'hir> {
pub(super) sess: &'a Session,
pub(super) resolver: &'a mut dyn ResolverAstLowering,
pub(super) nt_to_tokenstream: NtToTokenstream,
pub(super) arena: &'hir Arena<'hir>,
pub(super) ast_index: &'a IndexVec<LocalDefId, AstOwner<'a>>,
pub(super) owners: &'a mut IndexVec<LocalDefId, hir::MaybeOwner<&'hir hir::OwnerInfo<'hir>>>,
}

/// When we have a ty alias we *may* have two where clauses. To give the best diagnostics, we set the span
Expand All @@ -45,130 +52,140 @@ fn add_ty_alias_where_clause(
}
}

impl ItemLowerer<'_, '_, '_> {
fn with_trait_impl_ref<T>(
impl<'a, 'hir> ItemLowerer<'a, 'hir> {
fn with_lctx(
&mut self,
impl_ref: &Option<TraitRef>,
f: impl FnOnce(&mut Self) -> T,
) -> T {
let old = self.lctx.is_in_trait_impl;
self.lctx.is_in_trait_impl = impl_ref.is_some();
let ret = f(self);
self.lctx.is_in_trait_impl = old;
ret
}
}

impl<'a> Visitor<'a> for ItemLowerer<'a, '_, '_> {
fn visit_attribute(&mut self, _: &'a Attribute) {
// We do not want to lower expressions that appear in attributes,
// as they are not accessible to the rest of the HIR.
}
owner: NodeId,
f: impl FnOnce(&mut LoweringContext<'_, 'hir>) -> hir::OwnerNode<'hir>,
) {
let mut lctx = LoweringContext {
// Pseudo-globals.
sess: &self.sess,
resolver: self.resolver,
nt_to_tokenstream: self.nt_to_tokenstream,
arena: self.arena,

// HirId handling.
bodies: Vec::new(),
attrs: SortedMap::default(),
children: FxHashMap::default(),
current_hir_id_owner: CRATE_DEF_ID,
item_local_id_counter: hir::ItemLocalId::new(0),
node_id_to_local_id: Default::default(),
local_id_to_def_id: SortedMap::new(),
trait_map: Default::default(),

// Lowering state.
catch_scope: None,
loop_scope: None,
is_in_loop_condition: false,
is_in_trait_impl: false,
is_in_dyn_type: false,
anonymous_lifetime_mode: AnonymousLifetimeMode::PassThrough,
generator_kind: None,
task_context: None,
current_item: None,
lifetimes_to_define: Vec::new(),
is_collecting_anonymous_lifetimes: None,
in_scope_lifetimes: Vec::new(),
allow_try_trait: Some([sym::try_trait_v2][..].into()),
allow_gen_future: Some([sym::gen_future][..].into()),
allow_into_future: Some([sym::into_future][..].into()),
};
lctx.with_hir_id_owner(owner, |lctx| f(lctx));

fn visit_item(&mut self, item: &'a Item) {
let hir_id = self.lctx.with_hir_id_owner(item.id, |lctx| {
let node = lctx.without_in_scope_lifetime_defs(|lctx| lctx.lower_item(item));
hir::OwnerNode::Item(node)
});

self.lctx.with_parent_item_lifetime_defs(hir_id, |this| {
let this = &mut ItemLowerer { lctx: this };
match item.kind {
ItemKind::Impl(box Impl { ref of_trait, .. }) => {
this.with_trait_impl_ref(of_trait, |this| visit::walk_item(this, item));
}
_ => visit::walk_item(this, item),
}
});
for (def_id, info) in lctx.children {
self.owners.ensure_contains_elem(def_id, || hir::MaybeOwner::Phantom);
debug_assert!(matches!(self.owners[def_id], hir::MaybeOwner::Phantom));
self.owners[def_id] = info;
}
}

fn visit_fn(&mut self, fk: FnKind<'a>, sp: Span, _: NodeId) {
match fk {
FnKind::Fn(FnCtxt::Foreign, _, sig, _, _) => {
self.visit_fn_header(&sig.header);
visit::walk_fn_decl(self, &sig.decl);
// Don't visit the foreign function body even if it has one, since lowering the
// body would have no meaning and will have already been caught as a parse error.
pub(super) fn lower_node(
&mut self,
def_id: LocalDefId,
) -> hir::MaybeOwner<&'hir hir::OwnerInfo<'hir>> {
self.owners.ensure_contains_elem(def_id, || hir::MaybeOwner::Phantom);
if let hir::MaybeOwner::Phantom = self.owners[def_id] {
let node = self.ast_index[def_id];
match node {
AstOwner::NonOwner => {}
AstOwner::Crate(c) => self.lower_crate(c),
AstOwner::Item(item) => self.lower_item(item),
AstOwner::AssocItem(item, ctxt) => self.lower_assoc_item(item, ctxt),
AstOwner::ForeignItem(item) => self.lower_foreign_item(item),
}
_ => visit::walk_fn(self, fk, sp),
}
}

fn visit_assoc_item(&mut self, item: &'a AssocItem, ctxt: AssocCtxt) {
debug!(in_scope_lifetimes = ?self.lctx.in_scope_lifetimes);
self.lctx.with_hir_id_owner(item.id, |lctx| match ctxt {
AssocCtxt::Trait => hir::OwnerNode::TraitItem(lctx.lower_trait_item(item)),
AssocCtxt::Impl => hir::OwnerNode::ImplItem(lctx.lower_impl_item(item)),
});

visit::walk_assoc_item(self, item, ctxt);
self.owners[def_id]
}

fn visit_foreign_item(&mut self, item: &'a ForeignItem) {
self.lctx.with_hir_id_owner(item.id, |lctx| {
hir::OwnerNode::ForeignItem(lctx.lower_foreign_item(item))
});
fn lower_crate(&mut self, c: &Crate) {
debug_assert_eq!(self.resolver.local_def_id(CRATE_NODE_ID), CRATE_DEF_ID);

visit::walk_foreign_item(self, item);
self.with_lctx(CRATE_NODE_ID, |lctx| {
let module = lctx.lower_mod(&c.items, c.spans.inner_span);
lctx.lower_attrs(hir::CRATE_HIR_ID, &c.attrs);
hir::OwnerNode::Crate(lctx.arena.alloc(module))
})
}
}

impl<'hir> LoweringContext<'_, 'hir> {
// Same as the method above, but accepts `hir::GenericParam`s
// instead of `ast::GenericParam`s.
// This should only be used with generics that have already had their
// in-band lifetimes added. In practice, this means that this function is
// only used when lowering a child item of a trait or impl.
#[tracing::instrument(level = "debug", skip(self, f))]
fn with_parent_item_lifetime_defs<T>(
&mut self,
parent_hir_id: LocalDefId,
f: impl FnOnce(&mut Self) -> T,
) -> T {
let parent_generics = match self.owners[parent_hir_id].unwrap().node().expect_item().kind {
hir::ItemKind::Impl(hir::Impl { ref generics, .. })
| hir::ItemKind::Trait(_, _, ref generics, ..) => generics.params,
_ => &[],
};
let lt_def_names = parent_generics
.iter()
.filter_map(|param| match param.kind {
hir::GenericParamKind::Lifetime { .. } => {
Some(param.name.normalize_to_macros_2_0())
}
_ => None,
})
.collect();
let old_in_scope_lifetimes = mem::replace(&mut self.in_scope_lifetimes, lt_def_names);
debug!(in_scope_lifetimes = ?self.in_scope_lifetimes);

let res = f(self);

self.in_scope_lifetimes = old_in_scope_lifetimes;
res
fn lower_item(&mut self, item: &Item) {
self.with_lctx(item.id, |lctx| hir::OwnerNode::Item(lctx.lower_item(item)))
}

// Clears (and restores) the `in_scope_lifetimes` field. Used when
// visiting nested items, which never inherit in-scope lifetimes
// from their surrounding environment.
#[tracing::instrument(level = "debug", skip(self, f))]
fn without_in_scope_lifetime_defs<T>(&mut self, f: impl FnOnce(&mut Self) -> T) -> T {
let old_in_scope_lifetimes = mem::replace(&mut self.in_scope_lifetimes, vec![]);
debug!(?old_in_scope_lifetimes);
fn lower_assoc_item(&mut self, item: &AssocItem, ctxt: AssocCtxt) {
let def_id = self.resolver.local_def_id(item.id);

// this vector is only used when walking over impl headers,
// input types, and the like, and should not be non-empty in
// between items
assert!(self.lifetimes_to_define.is_empty());
let parent_id = {
let parent = self.resolver.definitions().def_key(def_id).parent;
let local_def_index = parent.unwrap();
LocalDefId { local_def_index }
};

let res = f(self);
let parent_hir = self.lower_node(parent_id).unwrap().node().expect_item();
self.with_lctx(item.id, |lctx| {
// Evaluate with the lifetimes in `params` in-scope.
// This is used to track which lifetimes have already been defined,
// and which need to be replicated when lowering an async fn.
match parent_hir.kind {
hir::ItemKind::Impl(hir::Impl { ref of_trait, ref generics, .. }) => {
lctx.is_in_trait_impl = of_trait.is_some();
lctx.in_scope_lifetimes = generics
.params
.iter()
.filter(|param| {
matches!(param.kind, hir::GenericParamKind::Lifetime { .. })
})
.map(|param| param.name)
.collect();
}
hir::ItemKind::Trait(_, _, ref generics, ..) => {
lctx.in_scope_lifetimes = generics
.params
.iter()
.filter(|param| {
matches!(param.kind, hir::GenericParamKind::Lifetime { .. })
})
.map(|param| param.name)
.collect();
}
_ => {}
};

assert!(self.in_scope_lifetimes.is_empty());
self.in_scope_lifetimes = old_in_scope_lifetimes;
match ctxt {
AssocCtxt::Trait => hir::OwnerNode::TraitItem(lctx.lower_trait_item(item)),
AssocCtxt::Impl => hir::OwnerNode::ImplItem(lctx.lower_impl_item(item)),
}
})
}

res
fn lower_foreign_item(&mut self, item: &ForeignItem) {
self.with_lctx(item.id, |lctx| hir::OwnerNode::ForeignItem(lctx.lower_foreign_item(item)))
}
}

impl<'hir> LoweringContext<'_, 'hir> {
pub(super) fn lower_mod(&mut self, items: &[P<Item>], inner: Span) -> hir::Mod<'hir> {
hir::Mod {
inner: self.lower_span(inner),
Expand Down Expand Up @@ -548,12 +565,11 @@ impl<'hir> LoweringContext<'_, 'hir> {
let new_id = self.resolver.local_def_id(new_node_id);
let Some(res) = resolutions.next() else {
// Associate an HirId to both ids even if there is no resolution.
self.owners.ensure_contains_elem(new_id, || hir::MaybeOwner::Phantom);
let _old = std::mem::replace(
&mut self.owners[new_id],
let _old = self.children.insert(
new_id,
hir::MaybeOwner::NonOwner(hir::HirId::make_owner(new_id)),
);
debug_assert!(matches!(_old, hir::MaybeOwner::Phantom));
debug_assert!(_old.is_none());
continue;
};
let ident = *ident;
Expand Down
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