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Tweak 'static suggestion code
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Fix #71196.
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estebank committed Apr 17, 2020
1 parent df768c5 commit de67990
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Showing 17 changed files with 532 additions and 149 deletions.
5 changes: 4 additions & 1 deletion src/librustc_ast_lowering/path.rs
Original file line number Diff line number Diff line change
Expand Up @@ -273,7 +273,10 @@ impl<'a, 'hir> LoweringContext<'a, 'hir> {
.next();
if !generic_args.parenthesized && !has_lifetimes {
generic_args.args = self
.elided_path_lifetimes(path_span, expected_lifetimes)
.elided_path_lifetimes(
first_generic_span.map(|s| s.shrink_to_lo()).unwrap_or(segment.ident.span),
expected_lifetimes,
)
.map(GenericArg::Lifetime)
.chain(generic_args.args.into_iter())
.collect();
Expand Down
185 changes: 97 additions & 88 deletions src/librustc_resolve/late/diagnostics.rs
Original file line number Diff line number Diff line change
Expand Up @@ -1035,101 +1035,110 @@ impl<'tcx> LifetimeContext<'_, 'tcx> {
lifetime_names: &FxHashSet<ast::Ident>,
params: &[ElisionFailureInfo],
) {
if count > 1 {
err.span_label(span, format!("expected {} lifetime parameters", count));
} else {
let snippet = self.tcx.sess.source_map().span_to_snippet(span).ok();
let suggest_existing = |err: &mut DiagnosticBuilder<'_>, sugg| {
err.span_suggestion(
span,
"consider using the named lifetime",
sugg,
Applicability::MaybeIncorrect,
);
};
let suggest_new = |err: &mut DiagnosticBuilder<'_>, sugg: &str| {
err.span_label(span, "expected named lifetime parameter");
err.span_label(
span,
&format!(
"expected {} lifetime parameter{}",
if count == 1 { "named".to_string() } else { count.to_string() },
pluralize!(count)
),
);

for missing in self.missing_named_lifetime_spots.iter().rev() {
let mut introduce_suggestion = vec![];
let msg;
let should_break;
introduce_suggestion.push(match missing {
MissingLifetimeSpot::Generics(generics) => {
msg = "consider introducing a named lifetime parameter".to_string();
should_break = true;
if let Some(param) = generics.params.iter().find(|p| match p.kind {
hir::GenericParamKind::Type {
synthetic: Some(hir::SyntheticTyParamKind::ImplTrait),
..
} => false,
_ => true,
}) {
(param.span.shrink_to_lo(), "'a, ".to_string())
} else {
(generics.span, "<'a>".to_string())
}
}
MissingLifetimeSpot::HigherRanked { span, span_type } => {
msg = format!(
"consider making the {} lifetime-generic with a new `'a` lifetime",
span_type.descr(),
);
should_break = false;
err.note(
"for more information on higher-ranked polymorphism, visit \
https://doc.rust-lang.org/nomicon/hrtb.html",
);
(*span, span_type.suggestion("'a"))
}
});
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!("&'a {}", &snippet[1..])));
} else if snippet.starts_with("&'_ ") {
introduce_suggestion
.push((param.span, format!("&'a {}", &snippet[4..])));
}
let snippet = self.tcx.sess.source_map().span_to_snippet(span).ok();
let suggest_existing = |err: &mut DiagnosticBuilder<'_>, sugg| {
err.span_suggestion_verbose(
span,
"consider using the named lifetime",
sugg,
Applicability::MaybeIncorrect,
);
};
let suggest_new = |err: &mut DiagnosticBuilder<'_>, sugg: &str| {
for missing in self.missing_named_lifetime_spots.iter().rev() {
let mut introduce_suggestion = vec![];
let msg;
let should_break;
introduce_suggestion.push(match missing {
MissingLifetimeSpot::Generics(generics) => {
msg = "consider introducing a named lifetime parameter".to_string();
should_break = true;
if let Some(param) = generics.params.iter().find(|p| match p.kind {
hir::GenericParamKind::Type {
synthetic: Some(hir::SyntheticTyParamKind::ImplTrait),
..
} => false,
_ => true,
}) {
(param.span.shrink_to_lo(), "'a, ".to_string())
} else {
(generics.span, "<'a>".to_string())
}
}
introduce_suggestion.push((span, sugg.to_string()));
err.multipart_suggestion(
&msg,
introduce_suggestion,
Applicability::MaybeIncorrect,
);
if should_break {
break;
MissingLifetimeSpot::HigherRanked { span, span_type } => {
msg = format!(
"consider making the {} lifetime-generic with a new `'a` lifetime",
span_type.descr(),
);
should_break = false;
err.note(
"for more information on higher-ranked polymorphism, visit \
https://doc.rust-lang.org/nomicon/hrtb.html",
);
(*span, span_type.suggestion("'a"))
}
});
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!("&'a {}", &snippet[1..])));
} else if snippet.starts_with("&'_ ") {
introduce_suggestion
.push((param.span, format!("&'a {}", &snippet[4..])));
}
}
}
};

match (lifetime_names.len(), lifetime_names.iter().next(), snippet.as_deref()) {
(1, Some(name), Some("&")) => {
suggest_existing(err, format!("&{} ", name));
}
(1, Some(name), Some("'_")) => {
suggest_existing(err, name.to_string());
}
(1, Some(name), Some(snippet)) if !snippet.ends_with('>') => {
suggest_existing(err, format!("{}<{}>", snippet, name));
}
(0, _, Some("&")) => {
suggest_new(err, "&'a ");
}
(0, _, Some("'_")) => {
suggest_new(err, "'a");
}
(0, _, Some(snippet)) if !snippet.ends_with('>') => {
suggest_new(err, &format!("{}<'a>", snippet));
}
_ => {
err.span_label(span, "expected lifetime parameter");
introduce_suggestion.push((span, sugg.to_string()));
err.multipart_suggestion(&msg, introduce_suggestion, Applicability::MaybeIncorrect);
if should_break {
break;
}
}
};

match (lifetime_names.len(), lifetime_names.iter().next(), snippet.as_deref()) {
(1, Some(name), Some("&")) => {
suggest_existing(err, format!("&{} ", name));
}
(1, Some(name), Some("'_")) => {
suggest_existing(err, name.to_string());
}
(1, Some(name), Some("")) => {
suggest_existing(err, format!("{}, ", name).repeat(count));
}
(1, Some(name), Some(snippet)) if !snippet.ends_with('>') => {
suggest_existing(
err,
format!(
"{}<{}>",
snippet,
std::iter::repeat(name.to_string())
.take(count)
.collect::<Vec<_>>()
.join(", ")
),
);
}
(0, _, Some("&")) if count == 1 => {
suggest_new(err, "&'a ");
}
(0, _, Some("'_")) if count == 1 => {
suggest_new(err, "'a");
}
(0, _, Some(snippet)) if !snippet.ends_with('>') && count == 1 => {
suggest_new(err, &format!("{}<'a>", snippet));
}
_ => {}
}
}
}
52 changes: 13 additions & 39 deletions src/librustc_resolve/late/lifetimes.rs
Original file line number Diff line number Diff line change
Expand Up @@ -2385,51 +2385,26 @@ impl<'a, 'tcx> LifetimeContext<'a, 'tcx> {
};

let mut err = self.report_missing_lifetime_specifiers(span, lifetime_refs.len());
let mut add_label = true;

if let Some(params) = error {
if lifetime_refs.len() == 1 {
add_label = add_label && self.report_elision_failure(&mut err, params, span);
if self.report_elision_failure(&mut err, params) && lifetime_names.is_empty() {
lifetime_names.insert(ast::Ident::from_str("'static"));
}
}
if add_label {
self.add_missing_lifetime_specifiers_label(
&mut err,
span,
lifetime_refs.len(),
&lifetime_names,
error.map(|p| &p[..]).unwrap_or(&[]),
);
}

self.add_missing_lifetime_specifiers_label(
&mut err,
span,
lifetime_refs.len(),
&lifetime_names,
error.map(|p| &p[..]).unwrap_or(&[]),
);
err.emit();
}

fn suggest_lifetime(&self, db: &mut DiagnosticBuilder<'_>, span: Span, msg: &str) -> bool {
match self.tcx.sess.source_map().span_to_snippet(span) {
Ok(ref snippet) => {
let (sugg, applicability) = if snippet == "&" {
("&'static ".to_owned(), Applicability::MachineApplicable)
} else if snippet == "'_" {
("'static".to_owned(), Applicability::MachineApplicable)
} else {
(format!("{} + 'static", snippet), Applicability::MaybeIncorrect)
};
db.span_suggestion(span, msg, sugg, applicability);
false
}
Err(_) => {
db.help(msg);
true
}
}
}

fn report_elision_failure(
&mut self,
db: &mut DiagnosticBuilder<'_>,
params: &[ElisionFailureInfo],
span: Span,
) -> bool {
let mut m = String::new();
let len = params.len();
Expand Down Expand Up @@ -2479,29 +2454,28 @@ impl<'a, 'tcx> LifetimeContext<'a, 'tcx> {
"this function's return type contains a borrowed value, \
but there is no value for it to be borrowed from",
);
self.suggest_lifetime(db, span, "consider giving it a 'static lifetime")
true
} else if elided_len == 0 {
db.help(
"this function's return type contains a borrowed value with \
an elided lifetime, but the lifetime cannot be derived from \
the arguments",
);
let msg = "consider giving it an explicit bounded or 'static lifetime";
self.suggest_lifetime(db, span, msg)
true
} else if elided_len == 1 {
db.help(&format!(
"this function's return type contains a borrowed value, \
but the signature does not say which {} it is borrowed from",
m
));
true
false
} else {
db.help(&format!(
"this function's return type contains a borrowed value, \
but the signature does not say whether it is borrowed from {}",
m
));
true
false
}
}

Expand Down
1 change: 1 addition & 0 deletions src/librustc_typeck/astconv.rs
Original file line number Diff line number Diff line change
Expand Up @@ -1727,6 +1727,7 @@ impl<'o, 'tcx> dyn AstConv<'tcx> + 'o {
self.ast_region_to_region(lifetime, None)
} else {
self.re_infer(None, span).unwrap_or_else(|| {
// FIXME: these can be redundant with E0106, but not always.
struct_span_err!(
tcx.sess,
span,
Expand Down
Original file line number Diff line number Diff line change
Expand Up @@ -2,9 +2,13 @@ error[E0106]: missing lifetime specifier
--> $DIR/bound-lifetime-in-binding-only.rs:52:23
|
LL | fn elision<T: Fn() -> &i32>() {
| ^ help: consider giving it a 'static lifetime: `&'static`
| ^ 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
help: consider using the named lifetime
|
LL | fn elision<T: Fn() -> &'static i32>() {
| ^^^^^^^^

error: aborting due to previous error

Expand Down
Original file line number Diff line number Diff line change
Expand Up @@ -2,9 +2,13 @@ error[E0106]: missing lifetime specifier
--> $DIR/bound-lifetime-in-return-only.rs:34:23
|
LL | fn elision(_: fn() -> &i32) {
| ^ help: consider giving it a 'static lifetime: `&'static`
| ^ 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
help: consider using the named lifetime
|
LL | fn elision(_: fn() -> &'static i32) {
| ^^^^^^^^

error: aborting due to previous error

Expand Down
6 changes: 5 additions & 1 deletion src/test/ui/async-await/issues/issue-63388-2.stderr
Original file line number Diff line number Diff line change
Expand Up @@ -4,9 +4,13 @@ error[E0106]: missing lifetime specifier
LL | foo: &dyn Foo, bar: &'a dyn Foo
| -------- -----------
LL | ) -> &dyn Foo
| ^ help: consider using the named lifetime: `&'a`
| ^ expected named lifetime parameter
|
= help: this function's return type contains a borrowed value, but the signature does not say whether it is borrowed from `foo` or `bar`
help: consider using the named lifetime
|
LL | ) -> &'a dyn Foo
| ^^^

error: aborting due to previous error

Expand Down
6 changes: 5 additions & 1 deletion src/test/ui/c-variadic/variadic-ffi-6.stderr
Original file line number Diff line number Diff line change
Expand Up @@ -2,9 +2,13 @@ error[E0106]: missing lifetime specifier
--> $DIR/variadic-ffi-6.rs:7:6
|
LL | ) -> &usize {
| ^ help: consider giving it an explicit bounded or 'static lifetime: `&'static`
| ^ expected named lifetime parameter
|
= help: this function's return type contains a borrowed value with an elided lifetime, but the lifetime cannot be derived from the arguments
help: consider using the named lifetime
|
LL | ) -> &'static usize {
| ^^^^^^^^

error: aborting due to previous error

Expand Down
6 changes: 5 additions & 1 deletion src/test/ui/foreign-fn-return-lifetime.stderr
Original file line number Diff line number Diff line change
Expand Up @@ -2,9 +2,13 @@ error[E0106]: missing lifetime specifier
--> $DIR/foreign-fn-return-lifetime.rs:5:19
|
LL | pub fn f() -> &u8;
| ^ help: consider giving it a 'static lifetime: `&'static`
| ^ 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
help: consider using the named lifetime
|
LL | pub fn f() -> &'static u8;
| ^^^^^^^^

error: aborting due to previous error

Expand Down
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