bjoernager/rust
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Remove in-band lifetimes

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This commit is contained in:
Michael Goulet 2022-02-09 18:42:32 -08:00
parent 4e82f35492
commit bb548a918a
67 changed files with 58 additions and 1459 deletions
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57
compiler/rustc_ast_lowering/src/lib.rs
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@ -142,13 +142,9 @@ struct LoweringContext<'a, 'hir: 'a> {
/// indicate whether or not we're in a place where new lifetimes will result
/// in in-band lifetime definitions, such a function or an impl header,
/// including implicit lifetimes from `impl_header_lifetime_elision`.
is_collecting_in_band_lifetimes: bool,
is_collecting_anonymous_lifetimes: bool,
/// Currently in-scope lifetimes defined in impl headers, fn headers, or HRTB.
/// When `is_collecting_in_band_lifetimes` is true, each lifetime is checked
/// against this list to see if it is already in-scope, or if a definition
/// needs to be created for it.
///
/// We always store a `normalize_to_macros_2_0()` version of the param-name in this
/// vector.
in_scope_lifetimes: Vec<ParamName>,
@ -379,7 +375,7 @@ pub fn lower_crate<'a, 'hir>(
task_context: None,
current_item: None,
lifetimes_to_define: Vec::new(),
is_collecting_in_band_lifetimes: false,
is_collecting_anonymous_lifetimes: false,
in_scope_lifetimes: Vec::new(),
allow_try_trait: Some([sym::try_trait_v2][..].into()),
allow_gen_future: Some([sym::gen_future][..].into()),
@ -726,13 +722,13 @@ impl<'a, 'hir> LoweringContext<'a, 'hir> {
&mut self,
f: impl FnOnce(&mut Self) -> T,
) -> (Vec<(Span, ParamName)>, T) {
let was_collecting = std::mem::replace(&mut self.is_collecting_in_band_lifetimes, true);
let was_collecting = std::mem::replace(&mut self.is_collecting_anonymous_lifetimes, true);
let len = self.lifetimes_to_define.len();
let res = f(self);
let lifetimes_to_define = self.lifetimes_to_define.split_off(len);
self.is_collecting_in_band_lifetimes = was_collecting;
self.is_collecting_anonymous_lifetimes = was_collecting;
(lifetimes_to_define, res)
}
@ -749,7 +745,7 @@ impl<'a, 'hir> LoweringContext<'a, 'hir> {
// that collisions are ok here and this shouldn't
// really show up for end-user.
let (str_name, kind) = match hir_name {
ParamName::Plain(ident) => (ident.name, hir::LifetimeParamKind::InBand),
ParamName::Plain(ident) => (ident.name, hir::LifetimeParamKind::Explicit),
ParamName::Fresh(_) => (kw::UnderscoreLifetime, hir::LifetimeParamKind::Elided),
ParamName::Error => (kw::UnderscoreLifetime, hir::LifetimeParamKind::Error),
};
@ -773,38 +769,10 @@ impl<'a, 'hir> LoweringContext<'a, 'hir> {
}
}
/// 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, ident: Ident) {
if !self.is_collecting_in_band_lifetimes {
return;
}
if !self.sess.features_untracked().in_band_lifetimes {
return;
}
if self.in_scope_lifetimes.contains(&ParamName::Plain(ident.normalize_to_macros_2_0())) {
return;
}
let hir_name = ParamName::Plain(ident);
if self.lifetimes_to_define.iter().any(|(_, lt_name)| {
lt_name.normalize_to_macros_2_0() == hir_name.normalize_to_macros_2_0()
}) {
return;
}
self.lifetimes_to_define.push((ident.span, hir_name));
}
/// When we have either an elided or `'_` lifetime in an impl
/// header, we convert it to an in-band lifetime.
fn collect_fresh_in_band_lifetime(&mut self, span: Span) -> ParamName {
assert!(self.is_collecting_in_band_lifetimes);
fn collect_fresh_anonymous_lifetime(&mut self, span: Span) -> ParamName {
assert!(self.is_collecting_anonymous_lifetimes);
let index = self.lifetimes_to_define.len() + self.in_scope_lifetimes.len();
let hir_name = ParamName::Fresh(index);
self.lifetimes_to_define.push((span, hir_name));
@ -1946,7 +1914,7 @@ impl<'a, 'hir> LoweringContext<'a, 'hir> {
}
ident if ident.name == kw::UnderscoreLifetime => match self.anonymous_lifetime_mode {
AnonymousLifetimeMode::CreateParameter => {
let fresh_name = self.collect_fresh_in_band_lifetime(span);
let fresh_name = self.collect_fresh_anonymous_lifetime(span);
self.new_named_lifetime(l.id, span, hir::LifetimeName::Param(fresh_name))
}
@ -1957,7 +1925,6 @@ impl<'a, 'hir> LoweringContext<'a, 'hir> {
AnonymousLifetimeMode::ReportError => self.new_error_lifetime(Some(l.id), span),
},
ident => {
self.maybe_collect_in_band_lifetime(ident);
let param_name = ParamName::Plain(self.lower_ident(ident));
self.new_named_lifetime(l.id, span, hir::LifetimeName::Param(param_name))
}
@ -2001,8 +1968,8 @@ impl<'a, 'hir> LoweringContext<'a, 'hir> {
let (name, kind) = match param.kind {
GenericParamKind::Lifetime => {
let was_collecting_in_band = self.is_collecting_in_band_lifetimes;
self.is_collecting_in_band_lifetimes = false;
let was_collecting_in_band = self.is_collecting_anonymous_lifetimes;
self.is_collecting_anonymous_lifetimes = false;
let lt = self
.with_anonymous_lifetime_mode(AnonymousLifetimeMode::ReportError, |this| {
@ -2025,7 +1992,7 @@ impl<'a, 'hir> LoweringContext<'a, 'hir> {
let kind =
hir::GenericParamKind::Lifetime { kind: hir::LifetimeParamKind::Explicit };
self.is_collecting_in_band_lifetimes = was_collecting_in_band;
self.is_collecting_anonymous_lifetimes = was_collecting_in_band;
(param_name, kind)
}
@ -2384,7 +2351,7 @@ impl<'a, 'hir> LoweringContext<'a, 'hir> {
// Hence `impl Foo for &u32` becomes `impl<'f> Foo for &'f u32` for some fresh
// `'f`.
AnonymousLifetimeMode::CreateParameter => {
let fresh_name = self.collect_fresh_in_band_lifetime(span);
let fresh_name = self.collect_fresh_anonymous_lifetime(span);
hir::Lifetime {
hir_id: self.next_id(),
span: self.lower_span(span),