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add a helper function maybe_collect_in_band_lifetime

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This commit is contained in:
Niko Matsakis 2018-03-21 04:57:57 -04:00
parent f71807d507
commit f07ebc5df8
1 changed files with 44 additions and 15 deletions
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59
src/librustc/hir/lowering.rs
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@ -600,6 +600,29 @@ impl<'a> LoweringContext<'a> {
(params, res)
}
/// When there is a reference to some lifetime `'a`, and in-band
/// lifetimes are enabled, then we want to push that lifetime into
/// the vector of names to define later. In that case, it will get
/// added to the appropriate generics.
fn maybe_collect_in_band_lifetime(&mut self, span: Span, name: Name) {
if !self.is_collecting_in_band_lifetimes {
return;
}
if self.in_scope_lifetimes.contains(&name) {
return;
}
if self.lifetimes_to_define
.iter()
.any(|(_, lt_name)| *lt_name == name)
{
return;
}
self.lifetimes_to_define.push((span, name));
}
// Evaluates `f` with the lifetimes in `lt_defs` in-scope.
// This is used to track which lifetimes have already been defined, and
// which are new in-band lifetimes that need to have a definition created
@ -1726,15 +1749,7 @@ impl<'a> LoweringContext<'a> {
x if x == "'_" => hir::LifetimeName::Underscore,
x if x == "'static" => hir::LifetimeName::Static,
name => {
if self.is_collecting_in_band_lifetimes && !self.in_scope_lifetimes.contains(&name)
&& self.lifetimes_to_define
.iter()
.find(|&&(_, lt_name)| lt_name == name)
.is_none()
{
self.lifetimes_to_define.push((l.span, name));
}
self.maybe_collect_in_band_lifetime(l.span, name);
hir::LifetimeName::Name(name)
}
};
@ -2132,18 +2147,32 @@ impl<'a> LoweringContext<'a> {
polarity,
defaultness,
ref ast_generics,
ref ifce,
ref trait_ref,
ref ty,
ref impl_items,
) => {
let def_id = self.resolver.definitions().local_def_id(id);
let (generics, (ifce, lowered_ty)) =
// Lower the "impl header" first. This ordering is important
// for in-band lifetimes! Consider `'a` here:
//
// impl Foo<'a> for u32 {
// fn method(&'a self) { .. }
// }
//
// Because we start by lowering the `Foo<'a> for u32`
// part, we will add `'a` to the list of generics on
// the impl. When we then encounter it later in the
// method, it will not be considered an in-band
// lifetime to be added, but rather a reference to a
// parent lifetime.
let (generics, (trait_ref, lowered_ty)) =
self.add_in_band_defs(ast_generics, def_id, |this| {
let ifce = ifce.as_ref().map(|trait_ref| {
let trait_ref = trait_ref.as_ref().map(|trait_ref| {
this.lower_trait_ref(trait_ref, ImplTraitContext::Disallowed)
});
if let Some(ref trait_ref) = ifce {
if let Some(ref trait_ref) = trait_ref {
if let Def::Trait(def_id) = trait_ref.path.def {
this.trait_impls.entry(def_id).or_insert(vec![]).push(id);
}
@ -2151,7 +2180,7 @@ impl<'a> LoweringContext<'a> {
let lowered_ty = this.lower_ty(ty, ImplTraitContext::Disallowed);
(ifce, lowered_ty)
(trait_ref, lowered_ty)
});
let new_impl_items = self.with_in_scope_lifetime_defs(
@ -2172,7 +2201,7 @@ impl<'a> LoweringContext<'a> {
self.lower_impl_polarity(polarity),
self.lower_defaultness(defaultness, true /* [1] */),
generics,
ifce,
trait_ref,
lowered_ty,
new_impl_items,
)