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Auto merge of #138965 - nnethercote:less-kw-Empty-hir-Lifetime, r=lcnr
Remove `kw::Empty` uses from `hir::Lifetime::ident` `hir::Lifetime::ident` is sometimes set to `kw::Empty` and it's really confusing. This PR stops that. Helps with #137978. r? `@lcnr`
2 parents 7586a9f + 8d2c63f commit 3f690c2

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10 files changed

+330
-82
lines changed

10 files changed

+330
-82
lines changed

Diff for: ‎compiler/rustc_ast_lowering/src/item.rs

+2-2
Original file line numberDiff line numberDiff line change
@@ -5,7 +5,7 @@ use rustc_ast::*;
55
use rustc_errors::ErrorGuaranteed;
66
use rustc_hir::def::{DefKind, Res};
77
use rustc_hir::def_id::{CRATE_DEF_ID, LocalDefId};
8-
use rustc_hir::{self as hir, HirId, PredicateOrigin};
8+
use rustc_hir::{self as hir, HirId, IsAnonInPath, PredicateOrigin};
99
use rustc_index::{IndexSlice, IndexVec};
1010
use rustc_middle::ty::{ResolverAstLowering, TyCtxt};
1111
use rustc_span::edit_distance::find_best_match_for_name;
@@ -1823,7 +1823,7 @@ impl<'hir> LoweringContext<'_, 'hir> {
18231823
}
18241824
GenericParamKind::Lifetime => {
18251825
let lt_id = self.next_node_id();
1826-
let lifetime = self.new_named_lifetime(id, lt_id, ident);
1826+
let lifetime = self.new_named_lifetime(id, lt_id, ident, IsAnonInPath::No);
18271827
hir::WherePredicateKind::RegionPredicate(hir::WhereRegionPredicate {
18281828
lifetime,
18291829
bounds,

Diff for: ‎compiler/rustc_ast_lowering/src/lib.rs

+34-13
Original file line numberDiff line numberDiff line change
@@ -55,7 +55,8 @@ use rustc_errors::{DiagArgFromDisplay, DiagCtxtHandle, StashKey};
5555
use rustc_hir::def::{DefKind, LifetimeRes, Namespace, PartialRes, PerNS, Res};
5656
use rustc_hir::def_id::{CRATE_DEF_ID, LOCAL_CRATE, LocalDefId};
5757
use rustc_hir::{
58-
self as hir, ConstArg, GenericArg, HirId, ItemLocalMap, LangItem, ParamName, TraitCandidate,
58+
self as hir, ConstArg, GenericArg, HirId, IsAnonInPath, ItemLocalMap, LangItem, ParamName,
59+
TraitCandidate,
5960
};
6061
use rustc_index::{Idx, IndexSlice, IndexVec};
6162
use rustc_macros::extension;
@@ -1755,7 +1756,11 @@ impl<'a, 'hir> LoweringContext<'a, 'hir> {
17551756
}
17561757

17571758
fn lower_lifetime(&mut self, l: &Lifetime) -> &'hir hir::Lifetime {
1758-
self.new_named_lifetime(l.id, l.id, l.ident)
1759+
self.new_named_lifetime(l.id, l.id, l.ident, IsAnonInPath::No)
1760+
}
1761+
1762+
fn lower_lifetime_anon_in_path(&mut self, id: NodeId, span: Span) -> &'hir hir::Lifetime {
1763+
self.new_named_lifetime(id, id, Ident::new(kw::UnderscoreLifetime, span), IsAnonInPath::Yes)
17591764
}
17601765

17611766
#[instrument(level = "debug", skip(self))]
@@ -1764,28 +1769,43 @@ impl<'a, 'hir> LoweringContext<'a, 'hir> {
17641769
id: NodeId,
17651770
new_id: NodeId,
17661771
ident: Ident,
1772+
is_anon_in_path: IsAnonInPath,
17671773
) -> &'hir hir::Lifetime {
1774+
debug_assert_ne!(ident.name, kw::Empty);
17681775
let res = self.resolver.get_lifetime_res(id).unwrap_or(LifetimeRes::Error);
17691776
let res = match res {
17701777
LifetimeRes::Param { param, .. } => hir::LifetimeName::Param(param),
17711778
LifetimeRes::Fresh { param, .. } => {
1779+
debug_assert_eq!(ident.name, kw::UnderscoreLifetime);
17721780
let param = self.local_def_id(param);
17731781
hir::LifetimeName::Param(param)
17741782
}
1775-
LifetimeRes::Infer => hir::LifetimeName::Infer,
1776-
LifetimeRes::Static { .. } => hir::LifetimeName::Static,
1783+
LifetimeRes::Infer => {
1784+
debug_assert_eq!(ident.name, kw::UnderscoreLifetime);
1785+
hir::LifetimeName::Infer
1786+
}
1787+
LifetimeRes::Static { .. } => {
1788+
debug_assert!(matches!(ident.name, kw::StaticLifetime | kw::UnderscoreLifetime));
1789+
hir::LifetimeName::Static
1790+
}
17771791
LifetimeRes::Error => hir::LifetimeName::Error,
17781792
LifetimeRes::ElidedAnchor { .. } => {
17791793
panic!("Unexpected `ElidedAnchar` {:?} at {:?}", ident, ident.span);
17801794
}
17811795
};
17821796

1797+
#[cfg(debug_assertions)]
1798+
if is_anon_in_path == IsAnonInPath::Yes {
1799+
debug_assert_eq!(ident.name, kw::UnderscoreLifetime);
1800+
}
1801+
17831802
debug!(?res);
1784-
self.arena.alloc(hir::Lifetime {
1785-
hir_id: self.lower_node_id(new_id),
1786-
ident: self.lower_ident(ident),
1803+
self.arena.alloc(hir::Lifetime::new(
1804+
self.lower_node_id(new_id),
1805+
self.lower_ident(ident),
17871806
res,
1788-
})
1807+
is_anon_in_path,
1808+
))
17891809
}
17901810

17911811
fn lower_generic_params_mut(
@@ -2369,11 +2389,12 @@ impl<'a, 'hir> LoweringContext<'a, 'hir> {
23692389
/// when the bound is written, even if it is written with `'_` like in
23702390
/// `Box<dyn Debug + '_>`. In those cases, `lower_lifetime` is invoked.
23712391
fn elided_dyn_bound(&mut self, span: Span) -> &'hir hir::Lifetime {
2372-
let r = hir::Lifetime {
2373-
hir_id: self.next_id(),
2374-
ident: Ident::new(kw::Empty, self.lower_span(span)),
2375-
res: hir::LifetimeName::ImplicitObjectLifetimeDefault,
2376-
};
2392+
let r = hir::Lifetime::new(
2393+
self.next_id(),
2394+
Ident::new(kw::UnderscoreLifetime, self.lower_span(span)),
2395+
hir::LifetimeName::ImplicitObjectLifetimeDefault,
2396+
IsAnonInPath::No,
2397+
);
23772398
debug!("elided_dyn_bound: r={:?}", r);
23782399
self.arena.alloc(r)
23792400
}

Diff for: ‎compiler/rustc_ast_lowering/src/path.rs

+2-5
Original file line numberDiff line numberDiff line change
@@ -7,7 +7,7 @@ use rustc_hir::def::{DefKind, PartialRes, Res};
77
use rustc_hir::def_id::DefId;
88
use rustc_middle::span_bug;
99
use rustc_session::parse::add_feature_diagnostics;
10-
use rustc_span::{BytePos, DUMMY_SP, DesugaringKind, Ident, Span, Symbol, kw, sym};
10+
use rustc_span::{BytePos, DUMMY_SP, DesugaringKind, Ident, Span, Symbol, sym};
1111
use smallvec::{SmallVec, smallvec};
1212
use tracing::{debug, instrument};
1313

@@ -450,10 +450,7 @@ impl<'a, 'hir> LoweringContext<'a, 'hir> {
450450
0,
451451
(start.as_u32()..end.as_u32()).map(|i| {
452452
let id = NodeId::from_u32(i);
453-
let l = self.lower_lifetime(&Lifetime {
454-
id,
455-
ident: Ident::new(kw::Empty, elided_lifetime_span),
456-
});
453+
let l = self.lower_lifetime_anon_in_path(id, elided_lifetime_span);
457454
GenericArg::Lifetime(l)
458455
}),
459456
);

Diff for: ‎compiler/rustc_borrowck/src/diagnostics/region_errors.rs

+3-3
Original file line numberDiff line numberDiff line change
@@ -513,14 +513,14 @@ impl<'infcx, 'tcx> MirBorrowckCtxt<'_, 'infcx, 'tcx> {
513513
ty::VarianceDiagInfo::Invariant { ty, param_index } => {
514514
let (desc, note) = match ty.kind() {
515515
ty::RawPtr(ty, mutbl) => {
516-
assert_eq!(*mutbl, rustc_hir::Mutability::Mut);
516+
assert_eq!(*mutbl, hir::Mutability::Mut);
517517
(
518518
format!("a mutable pointer to `{}`", ty),
519519
"mutable pointers are invariant over their type parameter".to_string(),
520520
)
521521
}
522522
ty::Ref(_, inner_ty, mutbl) => {
523-
assert_eq!(*mutbl, rustc_hir::Mutability::Mut);
523+
assert_eq!(*mutbl, hir::Mutability::Mut);
524524
(
525525
format!("a mutable reference to `{inner_ty}`"),
526526
"mutable references are invariant over their type parameter"
@@ -887,7 +887,7 @@ impl<'infcx, 'tcx> MirBorrowckCtxt<'_, 'infcx, 'tcx> {
887887
// Skip `async` desugaring `impl Future`.
888888
}
889889
if let TyKind::TraitObject(_, lt) = alias_ty.kind {
890-
if lt.ident.name == kw::Empty {
890+
if lt.res == hir::LifetimeName::ImplicitObjectLifetimeDefault {
891891
spans_suggs.push((lt.ident.span.shrink_to_hi(), " + 'a".to_string()));
892892
} else {
893893
spans_suggs.push((lt.ident.span, "'a".to_string()));

Diff for: ‎compiler/rustc_hir/src/hir.rs

+87-48
Original file line numberDiff line numberDiff line change
@@ -35,20 +35,60 @@ use crate::def_id::{DefId, LocalDefIdMap};
3535
pub(crate) use crate::hir_id::{HirId, ItemLocalId, ItemLocalMap, OwnerId};
3636
use crate::intravisit::{FnKind, VisitorExt};
3737

38+
#[derive(Debug, Copy, Clone, PartialEq, Eq, HashStable_Generic)]
39+
pub enum IsAnonInPath {
40+
No,
41+
Yes,
42+
}
43+
44+
/// A lifetime. The valid field combinations are non-obvious. The following
45+
/// example shows some of them. See also the comments on `LifetimeName`.
46+
/// ```
47+
/// #[repr(C)]
48+
/// struct S<'a>(&'a u32); // res=Param, name='a, IsAnonInPath::No
49+
/// unsafe extern "C" {
50+
/// fn f1(s: S); // res=Param, name='_, IsAnonInPath::Yes
51+
/// fn f2(s: S<'_>); // res=Param, name='_, IsAnonInPath::No
52+
/// fn f3<'a>(s: S<'a>); // res=Param, name='a, IsAnonInPath::No
53+
/// }
54+
///
55+
/// struct St<'a> { x: &'a u32 } // res=Param, name='a, IsAnonInPath::No
56+
/// fn f() {
57+
/// _ = St { x: &0 }; // res=Infer, name='_, IsAnonInPath::Yes
58+
/// _ = St::<'_> { x: &0 }; // res=Infer, name='_, IsAnonInPath::No
59+
/// }
60+
///
61+
/// struct Name<'a>(&'a str); // res=Param, name='a, IsAnonInPath::No
62+
/// const A: Name = Name("a"); // res=Static, name='_, IsAnonInPath::Yes
63+
/// const B: &str = ""; // res=Static, name='_, IsAnonInPath::No
64+
/// static C: &'_ str = ""; // res=Static, name='_, IsAnonInPath::No
65+
/// static D: &'static str = ""; // res=Static, name='static, IsAnonInPath::No
66+
///
67+
/// trait Tr {}
68+
/// fn tr(_: Box<dyn Tr>) {} // res=ImplicitObjectLifetimeDefault, name='_, IsAnonInPath::No
69+
///
70+
/// // (commented out because these cases trigger errors)
71+
/// // struct S1<'a>(&'a str); // res=Param, name='a, IsAnonInPath::No
72+
/// // struct S2(S1); // res=Error, name='_, IsAnonInPath::Yes
73+
/// // struct S3(S1<'_>); // res=Error, name='_, IsAnonInPath::No
74+
/// // struct S4(S1<'a>); // res=Error, name='a, IsAnonInPath::No
75+
/// ```
3876
#[derive(Debug, Copy, Clone, HashStable_Generic)]
3977
pub struct Lifetime {
4078
#[stable_hasher(ignore)]
4179
pub hir_id: HirId,
4280

43-
/// Either "`'a`", referring to a named lifetime definition,
44-
/// `'_` referring to an anonymous lifetime (either explicitly `'_` or `&type`),
45-
/// or "``" (i.e., `kw::Empty`) when appearing in path.
46-
///
47-
/// See `Lifetime::suggestion_position` for practical use.
81+
/// Either a named lifetime definition (e.g. `'a`, `'static`) or an
82+
/// anonymous lifetime (`'_`, either explicitly written, or inserted for
83+
/// things like `&type`).
4884
pub ident: Ident,
4985

5086
/// Semantics of this lifetime.
5187
pub res: LifetimeName,
88+
89+
/// Is the lifetime anonymous and in a path? Used only for error
90+
/// suggestions. See `Lifetime::suggestion` for example use.
91+
pub is_anon_in_path: IsAnonInPath,
5292
}
5393

5494
#[derive(Debug, Copy, Clone, HashStable_Generic)]
@@ -111,11 +151,12 @@ pub enum LifetimeName {
111151
/// that was already reported.
112152
Error,
113153

114-
/// User wrote an anonymous lifetime, either `'_` or nothing.
115-
/// The semantics of this lifetime should be inferred by typechecking code.
154+
/// User wrote an anonymous lifetime, either `'_` or nothing (which gets
155+
/// converted to `'_`). The semantics of this lifetime should be inferred
156+
/// by typechecking code.
116157
Infer,
117158

118-
/// User wrote `'static`.
159+
/// User wrote `'static` or nothing (which gets converted to `'_`).
119160
Static,
120161
}
121162

@@ -135,59 +176,57 @@ impl LifetimeName {
135176

136177
impl fmt::Display for Lifetime {
137178
fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
138-
if self.ident.name != kw::Empty { self.ident.name.fmt(f) } else { "'_".fmt(f) }
179+
self.ident.name.fmt(f)
139180
}
140181
}
141182

142-
pub enum LifetimeSuggestionPosition {
143-
/// The user wrote `'a` or `'_`.
144-
Normal,
145-
/// The user wrote `&type` or `&mut type`.
146-
Ampersand,
147-
/// The user wrote `Path` and omitted the `<'_>`.
148-
ElidedPath,
149-
/// The user wrote `Path<T>`, and omitted the `'_,`.
150-
ElidedPathArgument,
151-
/// The user wrote `dyn Trait` and omitted the `+ '_`.
152-
ObjectDefault,
153-
}
154-
155183
impl Lifetime {
184+
pub fn new(
185+
hir_id: HirId,
186+
ident: Ident,
187+
res: LifetimeName,
188+
is_anon_in_path: IsAnonInPath,
189+
) -> Lifetime {
190+
let lifetime = Lifetime { hir_id, ident, res, is_anon_in_path };
191+
192+
// Sanity check: elided lifetimes form a strict subset of anonymous lifetimes.
193+
#[cfg(debug_assertions)]
194+
match (lifetime.is_elided(), lifetime.is_anonymous()) {
195+
(false, false) => {} // e.g. `'a`
196+
(false, true) => {} // e.g. explicit `'_`
197+
(true, true) => {} // e.g. `&x`
198+
(true, false) => panic!("bad Lifetime"),
199+
}
200+
201+
lifetime
202+
}
203+
156204
pub fn is_elided(&self) -> bool {
157205
self.res.is_elided()
158206
}
159207

160208
pub fn is_anonymous(&self) -> bool {
161-
self.ident.name == kw::Empty || self.ident.name == kw::UnderscoreLifetime
162-
}
163-
164-
pub fn suggestion_position(&self) -> (LifetimeSuggestionPosition, Span) {
165-
if self.ident.name == kw::Empty {
166-
if self.ident.span.is_empty() {
167-
(LifetimeSuggestionPosition::ElidedPathArgument, self.ident.span)
168-
} else {
169-
(LifetimeSuggestionPosition::ElidedPath, self.ident.span.shrink_to_hi())
170-
}
171-
} else if self.res == LifetimeName::ImplicitObjectLifetimeDefault {
172-
(LifetimeSuggestionPosition::ObjectDefault, self.ident.span)
173-
} else if self.ident.span.is_empty() {
174-
(LifetimeSuggestionPosition::Ampersand, self.ident.span)
175-
} else {
176-
(LifetimeSuggestionPosition::Normal, self.ident.span)
177-
}
209+
self.ident.name == kw::UnderscoreLifetime
178210
}
179211

180212
pub fn suggestion(&self, new_lifetime: &str) -> (Span, String) {
181213
debug_assert!(new_lifetime.starts_with('\''));
182-
let (pos, span) = self.suggestion_position();
183-
let code = match pos {
184-
LifetimeSuggestionPosition::Normal => format!("{new_lifetime}"),
185-
LifetimeSuggestionPosition::Ampersand => format!("{new_lifetime} "),
186-
LifetimeSuggestionPosition::ElidedPath => format!("<{new_lifetime}>"),
187-
LifetimeSuggestionPosition::ElidedPathArgument => format!("{new_lifetime}, "),
188-
LifetimeSuggestionPosition::ObjectDefault => format!("+ {new_lifetime}"),
189-
};
190-
(span, code)
214+
215+
match (self.is_anon_in_path, self.ident.span.is_empty()) {
216+
// The user wrote `Path<T>`, and omitted the `'_,`.
217+
(IsAnonInPath::Yes, true) => (self.ident.span, format!("{new_lifetime}, ")),
218+
219+
// The user wrote `Path` and omitted the `<'_>`.
220+
(IsAnonInPath::Yes, false) => {
221+
(self.ident.span.shrink_to_hi(), format!("<{new_lifetime}>"))
222+
}
223+
224+
// The user wrote `&type` or `&mut type`.
225+
(IsAnonInPath::No, true) => (self.ident.span, format!("{new_lifetime} ")),
226+
227+
// The user wrote `'a` or `'_`.
228+
(IsAnonInPath::No, false) => (self.ident.span, format!("{new_lifetime}")),
229+
}
191230
}
192231
}
193232

Diff for: ‎compiler/rustc_hir/src/hir/tests.rs

+1
Original file line numberDiff line numberDiff line change
@@ -58,6 +58,7 @@ fn trait_object_roundtrips_impl(syntax: TraitObjectSyntax) {
5858
hir_id: HirId::INVALID,
5959
ident: Ident::new(sym::name, DUMMY_SP),
6060
res: LifetimeName::Static,
61+
is_anon_in_path: IsAnonInPath::No,
6162
}
6263
},
6364
syntax,

Diff for: ‎compiler/rustc_trait_selection/src/errors.rs

+11-8
Original file line numberDiff line numberDiff line change
@@ -9,7 +9,7 @@ use rustc_errors::{
99
use rustc_hir::def::DefKind;
1010
use rustc_hir::def_id::{DefId, LocalDefId};
1111
use rustc_hir::intravisit::{Visitor, VisitorExt, walk_ty};
12-
use rustc_hir::{self as hir, AmbigArg, FnRetTy, GenericParamKind, Node};
12+
use rustc_hir::{self as hir, AmbigArg, FnRetTy, GenericParamKind, IsAnonInPath, Node};
1313
use rustc_macros::{Diagnostic, Subdiagnostic};
1414
use rustc_middle::ty::print::{PrintTraitRefExt as _, TraitRefPrintOnlyTraitPath};
1515
use rustc_middle::ty::{self, Binder, ClosureKind, FnSig, Region, Ty, TyCtxt};
@@ -567,10 +567,14 @@ impl Subdiagnostic for AddLifetimeParamsSuggestion<'_> {
567567

568568
impl<'v> Visitor<'v> for ImplicitLifetimeFinder {
569569
fn visit_ty(&mut self, ty: &'v hir::Ty<'v, AmbigArg>) {
570-
let make_suggestion = |ident: Ident| {
571-
if ident.name == kw::Empty && ident.span.is_empty() {
570+
let make_suggestion = |lifetime: &hir::Lifetime| {
571+
if lifetime.is_anon_in_path == IsAnonInPath::Yes
572+
&& lifetime.ident.span.is_empty()
573+
{
572574
format!("{}, ", self.suggestion_param_name)
573-
} else if ident.name == kw::UnderscoreLifetime && ident.span.is_empty() {
575+
} else if lifetime.ident.name == kw::UnderscoreLifetime
576+
&& lifetime.ident.span.is_empty()
577+
{
574578
format!("{} ", self.suggestion_param_name)
575579
} else {
576580
self.suggestion_param_name.clone()
@@ -584,7 +588,7 @@ impl Subdiagnostic for AddLifetimeParamsSuggestion<'_> {
584588
matches!(
585589
arg,
586590
hir::GenericArg::Lifetime(lifetime)
587-
if lifetime.ident.name == kw::Empty
591+
if lifetime.is_anon_in_path == IsAnonInPath::Yes
588592
)
589593
}) {
590594
self.suggestions.push((
@@ -605,7 +609,7 @@ impl Subdiagnostic for AddLifetimeParamsSuggestion<'_> {
605609
{
606610
self.suggestions.push((
607611
lifetime.ident.span,
608-
make_suggestion(lifetime.ident),
612+
make_suggestion(lifetime),
609613
));
610614
}
611615
}
@@ -614,8 +618,7 @@ impl Subdiagnostic for AddLifetimeParamsSuggestion<'_> {
614618
}
615619
}
616620
hir::TyKind::Ref(lifetime, ..) if lifetime.is_anonymous() => {
617-
self.suggestions
618-
.push((lifetime.ident.span, make_suggestion(lifetime.ident)));
621+
self.suggestions.push((lifetime.ident.span, make_suggestion(lifetime)));
619622
}
620623
_ => {}
621624
}

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