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Clean up the lowering of AST items #88445

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Aug 31, 2021
Merged

Clean up the lowering of AST items #88445

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62 changes: 29 additions & 33 deletions compiler/rustc_ast_lowering/src/item.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -26,44 +26,43 @@ pub(super) struct ItemLowerer<'a, 'lowering, 'hir> {
}

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

impl<'a> Visitor<'a> for ItemLowerer<'a, '_, '_> {
fn visit_item(&mut self, item: &'a Item) {
let mut item_hir_id = None;
self.lctx.with_hir_id_owner(item.id, |lctx| {
let hir_id = self.lctx.with_hir_id_owner(item.id, |lctx| {
lctx.without_in_scope_lifetime_defs(|lctx| {
if let Some(hir_item) = lctx.lower_item(item) {
let id = lctx.insert_item(hir_item);
item_hir_id = Some(id);
}
let hir_item = lctx.lower_item(item);
lctx.insert_item(hir_item)
})
});

if let Some(hir_id) = item_hir_id {
self.lctx.with_parent_item_lifetime_defs(hir_id, |this| {
let this = &mut ItemLowerer { lctx: this };
match item.kind {
ItemKind::Mod(..) => {
let def_id = this.lctx.lower_node_id(item.id).expect_owner();
let old_current_module =
mem::replace(&mut this.lctx.current_module, def_id);
visit::walk_item(this, item);
this.lctx.current_module = old_current_module;
}
ItemKind::Impl(box ImplKind { ref of_trait, .. }) => {
this.with_trait_impl_ref(of_trait, |this| visit::walk_item(this, item));
}
_ => visit::walk_item(this, item),
self.lctx.with_parent_item_lifetime_defs(hir_id, |this| {
let this = &mut ItemLowerer { lctx: this };
match item.kind {
ItemKind::Mod(..) => {
let def_id = this.lctx.lower_node_id(item.id).expect_owner();
let old_current_module = mem::replace(&mut this.lctx.current_module, def_id);
visit::walk_item(this, item);
this.lctx.current_module = old_current_module;
}
});
}
ItemKind::Impl(box ImplKind { ref of_trait, .. }) => {
this.with_trait_impl_ref(of_trait, |this| visit::walk_item(this, item));
}
_ => visit::walk_item(this, item),
}
});
}

fn visit_fn(&mut self, fk: FnKind<'a>, sp: Span, _: NodeId) {
Expand Down Expand Up @@ -113,7 +112,7 @@ impl<'hir> LoweringContext<'_, 'hir> {
fn with_parent_item_lifetime_defs<T>(
&mut self,
parent_hir_id: hir::ItemId,
f: impl FnOnce(&mut LoweringContext<'_, '_>) -> T,
f: impl FnOnce(&mut Self) -> T,
) -> T {
let old_len = self.in_scope_lifetimes.len();

Expand All @@ -137,10 +136,7 @@ impl<'hir> LoweringContext<'_, 'hir> {
// Clears (and restores) the `in_scope_lifetimes` field. Used when
// visiting nested items, which never inherit in-scope lifetimes
// from their surrounding environment.
fn without_in_scope_lifetime_defs<T>(
&mut self,
f: impl FnOnce(&mut LoweringContext<'_, '_>) -> T,
) -> T {
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![]);

// this vector is only used when walking over impl headers,
Expand Down Expand Up @@ -208,19 +204,19 @@ impl<'hir> LoweringContext<'_, 'hir> {
}
}

pub fn lower_item(&mut self, i: &Item) -> Option<hir::Item<'hir>> {
pub fn lower_item(&mut self, i: &Item) -> hir::Item<'hir> {
let mut ident = i.ident;
let mut vis = self.lower_visibility(&i.vis, None);
let hir_id = self.lower_node_id(i.id);
let attrs = self.lower_attrs(hir_id, &i.attrs);
let kind = self.lower_item_kind(i.span, i.id, hir_id, &mut ident, attrs, &mut vis, &i.kind);
Some(hir::Item {
hir::Item {
def_id: hir_id.expect_owner(),
ident: self.lower_ident(ident),
kind,
vis,
span: self.lower_span(i.span),
})
}
}

fn lower_item_kind(
Expand Down