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When suggesting for lts, consider existing lifetime names

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Fix #72404.
This commit is contained in:
Esteban Küber 2020-08-10 16:42:57 -07:00
parent 7956b1cef7
commit b9585fda7b
6 changed files with 172 additions and 20 deletions
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75
src/librustc_resolve/late/diagnostics.rs
View file

@ -16,7 +16,7 @@ use rustc_hir::def_id::{DefId, CRATE_DEF_INDEX, LOCAL_CRATE};
use rustc_hir::PrimTy;
use rustc_session::config::nightly_options;
use rustc_span::hygiene::MacroKind;
use rustc_span::symbol::{kw, sym, Ident};
use rustc_span::symbol::{kw, sym, Ident, Symbol};
use rustc_span::{BytePos, Span, DUMMY_SP};
use log::debug;
@ -1244,7 +1244,8 @@ impl<'tcx> LifetimeContext<'_, 'tcx> {
err: &mut DiagnosticBuilder<'_>,
span: Span,
count: usize,
lifetime_names: &FxHashSet<Ident>,
lifetime_names: &FxHashSet<Symbol>,
lifetime_spans: Vec<Span>,
params: &[ElisionFailureInfo],
) {
let snippet = self.tcx.sess.source_map().span_to_snippet(span).ok();
@ -1258,11 +1259,60 @@ impl<'tcx> LifetimeContext<'_, 'tcx> {
),
);
let suggest_existing = |err: &mut DiagnosticBuilder<'_>, sugg| {
let suggest_existing = |err: &mut DiagnosticBuilder<'_>,
name: &str,
formatter: &dyn Fn(&str) -> String| {
if let Some(MissingLifetimeSpot::HigherRanked { span: for_span, span_type }) =
self.missing_named_lifetime_spots.iter().rev().next()
{
// When we have `struct S<'a>(&'a dyn Fn(&X) -> &X);` we want to not only suggest
// using `'a`, but also introduce the concept of HRLTs by suggesting
// `struct S<'a>(&'a dyn for<'b> Fn(&X) -> &'b X);`. (#72404)
let mut introduce_suggestion = vec![];
let a_to_z_repeat_n = |n| {
(b'a'..=b'z').map(move |c| {
let mut s = '\''.to_string();
s.extend(std::iter::repeat(char::from(c)).take(n));
s
})
};
// If all single char lifetime names are present, we wrap around and double the chars.
let lt_name = (1..)
.flat_map(a_to_z_repeat_n)
.find(|lt| !lifetime_names.contains(&Symbol::intern(&lt)))
.unwrap();
let msg = format!(
"consider making the {} lifetime-generic with a new `{}` lifetime",
span_type.descr(),
lt_name,
);
err.note(
"for more information on higher-ranked polymorphism, visit \
https://doc.rust-lang.org/nomicon/hrtb.html",
);
let for_sugg = span_type.suggestion(&lt_name);
for param in params {
if let Ok(snippet) = self.tcx.sess.source_map().span_to_snippet(param.span) {
if snippet.starts_with('&') && !snippet.starts_with("&'") {
introduce_suggestion
.push((param.span, format!("&{} {}", lt_name, &snippet[1..])));
} else if snippet.starts_with("&'_ ") {
introduce_suggestion
.push((param.span, format!("&{} {}", lt_name, &snippet[4..])));
}
}
}
introduce_suggestion.push((*for_span, for_sugg.to_string()));
introduce_suggestion.push((span, formatter(&lt_name)));
err.multipart_suggestion(&msg, introduce_suggestion, Applicability::MaybeIncorrect);
}
err.span_suggestion_verbose(
span,
&format!("consider using the `{}` lifetime", lifetime_names.iter().next().unwrap()),
sugg,
formatter(name),
Applicability::MaybeIncorrect,
);
};
@ -1330,17 +1380,16 @@ impl<'tcx> LifetimeContext<'_, 'tcx> {
match (lifetime_names.len(), lifetime_names.iter().next(), snippet.as_deref()) {
(1, Some(name), Some("&")) => {
suggest_existing(err, format!("&{} ", name));
suggest_existing(err, &name.as_str()[..], &|name| format!("&{} ", name));
}
(1, Some(name), Some("'_")) => {
suggest_existing(err, name.to_string());
suggest_existing(err, &name.as_str()[..], &|n| n.to_string());
}
(1, Some(name), Some("")) => {
suggest_existing(err, format!("{}, ", name).repeat(count));
suggest_existing(err, &name.as_str()[..], &|n| format!("{}, ", n).repeat(count));
}
(1, Some(name), Some(snippet)) if !snippet.ends_with('>') => {
suggest_existing(
err,
let f = |name: &str| {
format!(
"{}<{}>",
snippet,
@ -1348,8 +1397,9 @@ impl<'tcx> LifetimeContext<'_, 'tcx> {
.take(count)
.collect::<Vec<_>>()
.join(", ")
),
);
)
};
suggest_existing(err, &name.as_str()[..], &f);
}
(0, _, Some("&")) if count == 1 => {
suggest_new(err, "&'a ");
@ -1367,8 +1417,7 @@ impl<'tcx> LifetimeContext<'_, 'tcx> {
}
}
(n, ..) if n > 1 => {
let spans: Vec<Span> = lifetime_names.iter().map(|lt| lt.span).collect();
err.span_note(spans, "these named lifetimes are available to use");
err.span_note(lifetime_spans, "these named lifetimes are available to use");
if Some("") == snippet.as_deref() {
// This happens when we have `Foo<T>` where we point at the space before `T`,
// but this can be confusing so we give a suggestion with placeholders.

29
src/librustc_resolve/late/lifetimes.rs
View file

@ -2317,6 +2317,7 @@ impl<'a, 'tcx> LifetimeContext<'a, 'tcx> {
let mut late_depth = 0;
let mut scope = self.scope;
let mut lifetime_names = FxHashSet::default();
let mut lifetime_spans = vec![];
let error = loop {
match *scope {
// Do not assign any resolution, it will be inferred.
@ -2328,7 +2329,8 @@ impl<'a, 'tcx> LifetimeContext<'a, 'tcx> {
// collect named lifetimes for suggestions
for name in lifetimes.keys() {
if let hir::ParamName::Plain(name) = name {
lifetime_names.insert(*name);
lifetime_names.insert(name.name);
lifetime_spans.push(name.span);
}
}
late_depth += 1;
@ -2346,12 +2348,24 @@ impl<'a, 'tcx> LifetimeContext<'a, 'tcx> {
}
Elide::Exact(l) => l.shifted(late_depth),
Elide::Error(ref e) => {
if let Scope::Binder { ref lifetimes, .. } = s {
// collect named lifetimes for suggestions
for name in lifetimes.keys() {
if let hir::ParamName::Plain(name) = name {
lifetime_names.insert(*name);
let mut scope = s;
loop {
match scope {
Scope::Binder { ref lifetimes, s, .. } => {
// Collect named lifetimes for suggestions.
for name in lifetimes.keys() {
if let hir::ParamName::Plain(name) = name {
lifetime_names.insert(name.name);
lifetime_spans.push(name.span);
}
}
scope = s;
}
Scope::ObjectLifetimeDefault { ref s, .. }
| Scope::Elision { ref s, .. } => {
scope = s;
}
_ => break,
}
}
break Some(e);
@ -2375,7 +2389,7 @@ impl<'a, 'tcx> LifetimeContext<'a, 'tcx> {
if let Some(params) = error {
// If there's no lifetime available, suggest `'static`.
if self.report_elision_failure(&mut err, params) && lifetime_names.is_empty() {
lifetime_names.insert(Ident::with_dummy_span(kw::StaticLifetime));
lifetime_names.insert(kw::StaticLifetime);
}
}
self.add_missing_lifetime_specifiers_label(
@ -2383,6 +2397,7 @@ impl<'a, 'tcx> LifetimeContext<'a, 'tcx> {
span,
lifetime_refs.len(),
&lifetime_names,
lifetime_spans,
error.map(|p| &p[..]).unwrap_or(&[]),
);
err.emit();

5
src/test/ui/associated-types/bound-lifetime-in-binding-only.elision.stderr
View file

@ -5,6 +5,11 @@ LL | fn elision<T: Fn() -> &i32>() {
| ^ expected named lifetime parameter
|
= help: this function's return type contains a borrowed value, but there is no value for it to be borrowed from
= 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 `'a` lifetime
|
LL | fn elision<T: for<'a> Fn() -> &'a i32>() {
| ^^^^^^^ ^^^
help: consider using the `'static` lifetime
|
LL | fn elision<T: Fn() -> &'static i32>() {

5
src/test/ui/associated-types/bound-lifetime-in-return-only.elision.stderr
View file

@ -5,6 +5,11 @@ LL | fn elision(_: fn() -> &i32) {
| ^ expected named lifetime parameter
|
= help: this function's return type contains a borrowed value, but there is no value for it to be borrowed from
= note: for more information on higher-ranked polymorphism, visit https://doc.rust-lang.org/nomicon/hrtb.html
help: consider making the type lifetime-generic with a new `'a` lifetime
|
LL | fn elision(_: for<'a> fn() -> &'a i32) {
| ^^^^^^^ ^^^
help: consider using the `'static` lifetime
|
LL | fn elision(_: fn() -> &'static i32) {

15
src/test/ui/suggestions/missing-lt-for-hrtb.rs Normal file
View file

@ -0,0 +1,15 @@
struct X<'a>(&'a ());
struct S<'a>(&'a dyn Fn(&X) -> &X);
//~^ ERROR missing lifetime specifier
//~| ERROR missing lifetime specifier
struct V<'a>(&'a dyn for<'b> Fn(&X) -> &X);
//~^ ERROR missing lifetime specifier
//~| ERROR missing lifetime specifier
fn main() {
let x = S(&|x| {
println!("hi");
x
});
x.0(&X(&()));
}

63
src/test/ui/suggestions/missing-lt-for-hrtb.stderr Normal file
View file

@ -0,0 +1,63 @@
error[E0106]: missing lifetime specifier
--> $DIR/missing-lt-for-hrtb.rs:2:32
|
LL | struct S<'a>(&'a dyn Fn(&X) -> &X);
| -- ^ expected named lifetime parameter
|
= help: this function's return type contains a borrowed value, but the signature does not say which one of argument 1's 2 lifetimes it is borrowed from
= 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 | struct S<'a>(&'a dyn for<'b> Fn(&'b X) -> &'b X);
| ^^^^^^^ ^^^^^ ^^^
help: consider using the `'a` lifetime
|
LL | struct S<'a>(&'a dyn Fn(&X) -> &'a X);
| ^^^
error[E0106]: missing lifetime specifier
--> $DIR/missing-lt-for-hrtb.rs:2:33
|
LL | struct S<'a>(&'a dyn Fn(&X) -> &X);
| -- ^ expected named lifetime parameter
|
= help: this function's return type contains a borrowed value, but the signature does not say which one of argument 1's 2 lifetimes it is borrowed from
= 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 | struct S<'a>(&'a dyn for<'b> Fn(&'b X) -> &X<'b>);
| ^^^^^^^ ^^^^^ ^^^^^
help: consider using the `'a` lifetime
|
LL | struct S<'a>(&'a dyn Fn(&X) -> &X<'a>);
| ^^^^^
error[E0106]: missing lifetime specifier
--> $DIR/missing-lt-for-hrtb.rs:5:40
|
LL | struct V<'a>(&'a dyn for<'b> Fn(&X) -> &X);
| -- ^ expected named lifetime parameter
|
= help: this function's return type contains a borrowed value, but the signature does not say which one of argument 1's 2 lifetimes it is borrowed from
note: these named lifetimes are available to use
--> $DIR/missing-lt-for-hrtb.rs:5:10
|
LL | struct V<'a>(&'a dyn for<'b> Fn(&X) -> &X);
| ^^ ^^
error[E0106]: missing lifetime specifier
--> $DIR/missing-lt-for-hrtb.rs:5:41
|
LL | struct V<'a>(&'a dyn for<'b> Fn(&X) -> &X);
| -- ^ expected named lifetime parameter
|
= help: this function's return type contains a borrowed value, but the signature does not say which one of argument 1's 2 lifetimes it is borrowed from
note: these named lifetimes are available to use
--> $DIR/missing-lt-for-hrtb.rs:5:10
|
LL | struct V<'a>(&'a dyn for<'b> Fn(&X) -> &X);
| ^^ ^^
error: aborting due to 4 previous errors
For more information about this error, try `rustc --explain E0106`.