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Fix incorrect suggestion for undeclared hrtb lifetimes in where clauses.
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fixes rust-lang#122714
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@surechen
surechen committed May 20, 2024
1 parent e8ada6a commit 4ebbb5f
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Showing 3 changed files with 207 additions and 14 deletions.
101 changes: 87 additions & 14 deletions compiler/rustc_resolve/src/late/diagnostics.rs
View file
Original file line number Diff line number Diff line change
Expand Up @@ -17,6 +17,7 @@ use rustc_ast::{
};
use rustc_ast_pretty::pprust::where_bound_predicate_to_string;
use rustc_data_structures::fx::FxHashSet;
use rustc_data_structures::fx::FxIndexSet;
use rustc_errors::{
codes::*, pluralize, struct_span_code_err, Applicability, Diag, ErrorGuaranteed, MultiSpan,
SuggestionStyle,
Expand All @@ -31,7 +32,7 @@ use rustc_span::edit_distance::find_best_match_for_name;
use rustc_span::edition::Edition;
use rustc_span::hygiene::MacroKind;
use rustc_span::symbol::{kw, sym, Ident, Symbol};
use rustc_span::Span;
use rustc_span::{Span, DUMMY_SP};

use rustc_middle::ty;

Expand Down Expand Up @@ -2714,8 +2715,17 @@ impl<'a: 'ast, 'ast, 'tcx> LateResolutionVisitor<'a, '_, 'ast, 'tcx> {
self.suggest_introducing_lifetime(
&mut err,
Some(lifetime_ref.ident.name.as_str()),
|err, _, span, message, suggestion| {
err.span_suggestion(span, message, suggestion, Applicability::MaybeIncorrect);
|err, _, span, message, suggestion, span_suggs| {
err.multipart_suggestion_with_style(
message,
std::iter::once((span, suggestion)).chain(span_suggs.clone()).collect(),
Applicability::MaybeIncorrect,
if span_suggs.is_empty() {
SuggestionStyle::ShowCode
} else {
SuggestionStyle::ShowAlways
},
);
true
},
);
Expand All @@ -2726,13 +2736,20 @@ impl<'a: 'ast, 'ast, 'tcx> LateResolutionVisitor<'a, '_, 'ast, 'tcx> {
&self,
err: &mut Diag<'_>,
name: Option<&str>,
suggest: impl Fn(&mut Diag<'_>, bool, Span, Cow<'static, str>, String) -> bool,
suggest: impl Fn(
&mut Diag<'_>,
bool,
Span,
Cow<'static, str>,
String,
Vec<(Span, String)>,
) -> bool,
) {
let mut suggest_note = true;
for rib in self.lifetime_ribs.iter().rev() {
let mut should_continue = true;
match rib.kind {
LifetimeRibKind::Generics { binder: _, span, kind } => {
LifetimeRibKind::Generics { binder, span, kind } => {
// Avoid suggesting placing lifetime parameters on constant items unless the relevant
// feature is enabled. Suggest the parent item as a possible location if applicable.
if let LifetimeBinderKind::ConstItem = kind
Expand Down Expand Up @@ -2761,11 +2778,53 @@ impl<'a: 'ast, 'ast, 'tcx> LateResolutionVisitor<'a, '_, 'ast, 'tcx> {
| LifetimeBinderKind::PolyTrait
| LifetimeBinderKind::WhereBound
);

let mut rm_inner_binders: FxIndexSet<Span> = Default::default();
let (span, sugg) = if span.is_empty() {
let mut binder_idents: FxIndexSet<Ident> = Default::default();
binder_idents.insert(Ident::from_str(name.unwrap_or("'a")));

// We need to special case binders in the following situation:
// Change `T: for<'a> Trait<T> + 'b` to `for<'a, 'b> T: Trait<T> + 'b`
// T: for<'a> Trait<T> + 'b
// ^^^^^^^ remove existing inner binder `for<'a>`
// for<'a, 'b> T: Trait<T> + 'b
// ^^^^^^^^^^^ suggest outer binder `for<'a, 'b>`
if let LifetimeBinderKind::WhereBound = kind
&& let Some(ast::WherePredicate::BoundPredicate(
ast::WhereBoundPredicate { bounded_ty, bounds, .. },
)) = self.diag_metadata.current_where_predicate
&& bounded_ty.id == binder
{
for bound in bounds {
if let ast::GenericBound::Trait(poly_trait_ref, _) = bound
&& let span = poly_trait_ref
.span
.with_hi(poly_trait_ref.trait_ref.path.span.lo())
&& !span.is_empty()
{
rm_inner_binders.insert(span);
poly_trait_ref.bound_generic_params.iter().for_each(|v| {
binder_idents.insert(v.ident);
});
}
}
}

let binders_sugg = binder_idents.into_iter().enumerate().fold(
"".to_string(),
|mut binders, (i, x)| {
if i != 0 {
binders += ", ";
}
binders += x.as_str();
binders
},
);
let sugg = format!(
"{}<{}>{}",
if higher_ranked { "for" } else { "" },
name.unwrap_or("'a"),
binders_sugg,
if higher_ranked { " " } else { "" },
);
(span, sugg)
Expand All @@ -2780,24 +2839,39 @@ impl<'a: 'ast, 'ast, 'tcx> LateResolutionVisitor<'a, '_, 'ast, 'tcx> {
let sugg = format!("{}, ", name.unwrap_or("'a"));
(span, sugg)
};

if higher_ranked {
let message = Cow::from(format!(
"consider making the {} lifetime-generic with a new `{}` lifetime",
kind.descr(),
name.unwrap_or("'a"),
));
should_continue = suggest(err, true, span, message, sugg);
should_continue = suggest(
err,
true,
span,
message,
sugg,
if !rm_inner_binders.is_empty() {
rm_inner_binders
.into_iter()
.map(|v| (v, "".to_string()))
.collect::<Vec<_>>()
} else {
vec![]
},
);
err.note_once(
"for more information on higher-ranked polymorphism, visit \
https://doc.rust-lang.org/nomicon/hrtb.html",
);
} else if let Some(name) = name {
let message =
Cow::from(format!("consider introducing lifetime `{name}` here"));
should_continue = suggest(err, false, span, message, sugg);
should_continue = suggest(err, false, span, message, sugg, vec![]);
} else {
let message = Cow::from("consider introducing a named lifetime parameter");
should_continue = suggest(err, false, span, message, sugg);
should_continue = suggest(err, false, span, message, sugg, vec![]);
}
}
LifetimeRibKind::Item | LifetimeRibKind::ConstParamTy => break,
Expand Down Expand Up @@ -3033,11 +3107,11 @@ impl<'a: 'ast, 'ast, 'tcx> LateResolutionVisitor<'a, '_, 'ast, 'tcx> {
self.suggest_introducing_lifetime(
err,
None,
|err, higher_ranked, span, message, intro_sugg| {
|err, higher_ranked, span, message, intro_sugg, _| {
err.multipart_suggestion_verbose(
message,
std::iter::once((span, intro_sugg))
.chain(spans_suggs.iter().cloned())
.chain(spans_suggs.clone())
.collect(),
Applicability::MaybeIncorrect,
);
Expand Down Expand Up @@ -3161,11 +3235,11 @@ impl<'a: 'ast, 'ast, 'tcx> LateResolutionVisitor<'a, '_, 'ast, 'tcx> {
self.suggest_introducing_lifetime(
err,
None,
|err, higher_ranked, span, message, intro_sugg| {
|err, higher_ranked, span, message, intro_sugg, _| {
err.multipart_suggestion_verbose(
message,
std::iter::once((span, intro_sugg))
.chain(spans_suggs.iter().cloned())
.chain(spans_suggs.clone())
.collect(),
Applicability::MaybeIncorrect,
);
Expand Down Expand Up @@ -3309,7 +3383,6 @@ fn mk_where_bound_predicate(
poly_trait_ref: &ast::PolyTraitRef,
ty: &Ty,
) -> Option<ast::WhereBoundPredicate> {
use rustc_span::DUMMY_SP;
let modified_segments = {
let mut segments = path.segments.clone();
let [preceding @ .., second_last, last] = segments.as_mut_slice() else {
Expand Down
28 changes: 28 additions & 0 deletions tests/ui/generics/generic-higher-ranked-lifetime-issue-122714.rs
View file
Original file line number Diff line number Diff line change
@@ -0,0 +1,28 @@
#![allow(dead_code)]

trait Trait1<T>
where T: for<'a> Trait1<T> + 'b { } //~ ERROR use of undeclared lifetime name `'b`

trait Trait2<T>
where
T: B<'b> + for<'a> A<'a>, //~ ERROR use of undeclared lifetime name `'b`
{
}

trait Trait3<T>
where
T: B<'b> + for<'a> A<'a> + 'c {}
//~^ ERROR use of undeclared lifetime name `'b`
//~| ERROR use of undeclared lifetime name `'c`

trait Trait4<T>
where
T: for<'a> A<'a> + 'x + for<'b> B<'b>, //~ ERROR use of undeclared lifetime name `'x`
{
}

trait A<'a> {}
trait B<'a> {}


fn main() {}
92 changes: 92 additions & 0 deletions tests/ui/generics/generic-higher-ranked-lifetime-issue-122714.stderr
View file
Original file line number Diff line number Diff line change
@@ -0,0 +1,92 @@
error[E0261]: use of undeclared lifetime name `'b`
--> $DIR/generic-higher-ranked-lifetime-issue-122714.rs:4:32
|
LL | where T: for<'a> Trait1<T> + 'b { }
| ^^ undeclared lifetime
|
= note: for more information on higher-ranked polymorphism, visit https://doc.rust-lang.org/nomicon/hrtb.html
help: consider making the bound lifetime-generic with a new `'b` lifetime
|
LL - where T: for<'a> Trait1<T> + 'b { }
LL + where for<'b, 'a> T: Trait1<T> + 'b { }
|
help: consider introducing lifetime `'b` here
|
LL | trait Trait1<'b, T>
| +++

error[E0261]: use of undeclared lifetime name `'b`
--> $DIR/generic-higher-ranked-lifetime-issue-122714.rs:8:10
|
LL | T: B<'b> + for<'a> A<'a>,
| ^^ undeclared lifetime
|
help: consider making the bound lifetime-generic with a new `'b` lifetime
|
LL | T: for<'b> B<'b> + for<'a> A<'a>,
| +++++++
help: consider making the bound lifetime-generic with a new `'b` lifetime
|
LL - T: B<'b> + for<'a> A<'a>,
LL + for<'b, 'a> T: B<'b> + A<'a>,
|
help: consider introducing lifetime `'b` here
|
LL | trait Trait2<'b, T>
| +++

error[E0261]: use of undeclared lifetime name `'b`
--> $DIR/generic-higher-ranked-lifetime-issue-122714.rs:14:10
|
LL | T: B<'b> + for<'a> A<'a> + 'c {}
| ^^ undeclared lifetime
|
help: consider making the bound lifetime-generic with a new `'b` lifetime
|
LL | T: for<'b> B<'b> + for<'a> A<'a> + 'c {}
| +++++++
help: consider making the bound lifetime-generic with a new `'b` lifetime
|
LL - T: B<'b> + for<'a> A<'a> + 'c {}
LL + for<'b, 'a> T: B<'b> + A<'a> + 'c {}
|
help: consider introducing lifetime `'b` here
|
LL | trait Trait3<'b, T>
| +++

error[E0261]: use of undeclared lifetime name `'c`
--> $DIR/generic-higher-ranked-lifetime-issue-122714.rs:14:32
|
LL | T: B<'b> + for<'a> A<'a> + 'c {}
| ^^ undeclared lifetime
|
help: consider making the bound lifetime-generic with a new `'c` lifetime
|
LL - T: B<'b> + for<'a> A<'a> + 'c {}
LL + for<'c, 'a> T: B<'b> + A<'a> + 'c {}
|
help: consider introducing lifetime `'c` here
|
LL | trait Trait3<'c, T>
| +++

error[E0261]: use of undeclared lifetime name `'x`
--> $DIR/generic-higher-ranked-lifetime-issue-122714.rs:20:24
|
LL | T: for<'a> A<'a> + 'x + for<'b> B<'b>,
| ^^ undeclared lifetime
|
help: consider making the bound lifetime-generic with a new `'x` lifetime
|
LL - T: for<'a> A<'a> + 'x + for<'b> B<'b>,
LL + for<'x, 'a, 'b> T: A<'a> + 'x + B<'b>,
|
help: consider introducing lifetime `'x` here
|
LL | trait Trait4<'x, T>
| +++

error: aborting due to 5 previous errors

For more information about this error, try `rustc --explain E0261`.

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