From 795d307f10ec0fd3851b18a3365755d76b7403e5 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Esteban=20K=C3=BCber?= <esteban@kuber.com.ar>
Date: Tue, 12 Mar 2019 14:57:13 -0700
Subject: [PATCH 1/3] Suggest return lifetime when there's only one named
lifetime
---
src/librustc/middle/resolve_lifetime.rs | 37 +++++++++++++++++--
.../ui/suggestions/return-without-lifetime.rs | 8 ++++
.../return-without-lifetime.stderr | 19 ++++++++++
3 files changed, 60 insertions(+), 4 deletions(-)
create mode 100644 src/test/ui/suggestions/return-without-lifetime.rs
create mode 100644 src/test/ui/suggestions/return-without-lifetime.stderr
diff --git a/src/librustc/middle/resolve_lifetime.rs b/src/librustc/middle/resolve_lifetime.rs
index f862b690f8806..35bca04d1e623 100644
--- a/src/librustc/middle/resolve_lifetime.rs
+++ b/src/librustc/middle/resolve_lifetime.rs
@@ -2298,6 +2298,7 @@ impl<'a, 'tcx> LifetimeContext<'a, 'tcx> {
let span = lifetime_refs[0].span;
let mut late_depth = 0;
let mut scope = self.scope;
+ let mut lifetime_names = FxHashSet::default();
let error = loop {
match *scope {
// Do not assign any resolution, it will be inferred.
@@ -2310,7 +2311,7 @@ impl<'a, 'tcx> LifetimeContext<'a, 'tcx> {
scope = s;
}
- Scope::Elision { ref elide, .. } => {
+ Scope::Elision { ref elide, ref s, .. } => {
let lifetime = match *elide {
Elide::FreshLateAnon(ref counter) => {
for lifetime_ref in lifetime_refs {
@@ -2320,7 +2321,16 @@ impl<'a, 'tcx> LifetimeContext<'a, 'tcx> {
return;
}
Elide::Exact(l) => l.shifted(late_depth),
- Elide::Error(ref e) => break Some(e),
+ Elide::Error(ref e) => {
+ if let Scope::Binder { ref lifetimes, .. } = s {
+ for name in lifetimes.keys() {
+ if let hir::ParamName::Plain(name) = name {
+ lifetime_names.insert(*name);
+ }
+ }
+ }
+ break Some(e);
+ }
};
for lifetime_ref in lifetime_refs {
self.insert_lifetime(lifetime_ref, lifetime);
@@ -2343,7 +2353,13 @@ impl<'a, 'tcx> LifetimeContext<'a, 'tcx> {
}
}
if add_label {
- add_missing_lifetime_specifiers_label(&mut err, span, lifetime_refs.len());
+ add_missing_lifetime_specifiers_label(
+ &mut err,
+ span,
+ lifetime_refs.len(),
+ &lifetime_names,
+ self.tcx.sess.source_map().span_to_snippet(span).ok().as_ref().map(|s| s.as_str()),
+ );
}
err.emit();
@@ -2884,10 +2900,23 @@ fn add_missing_lifetime_specifiers_label(
err: &mut DiagnosticBuilder<'_>,
span: Span,
count: usize,
+ lifetime_names: &FxHashSet<ast::Ident>,
+ snippet: Option<&str>,
) {
if count > 1 {
err.span_label(span, format!("expected {} lifetime parameters", count));
+ } else if let (1, Some(name), Some("&")) = (
+ lifetime_names.len(),
+ lifetime_names.iter().next(),
+ snippet,
+ ) {
+ err.span_suggestion(
+ span,
+ &format!("consider using the named lifetime `{}`", name),
+ format!("&{} ", name),
+ Applicability::MaybeIncorrect,
+ );
} else {
err.span_label(span, "expected lifetime parameter");
- };
+ }
}
diff --git a/src/test/ui/suggestions/return-without-lifetime.rs b/src/test/ui/suggestions/return-without-lifetime.rs
new file mode 100644
index 0000000000000..5f19e93013acf
--- /dev/null
+++ b/src/test/ui/suggestions/return-without-lifetime.rs
@@ -0,0 +1,8 @@
+struct Thing<'a>(&'a ());
+
+fn func1<'a>(_arg: &'a Thing) -> &() { unimplemented!() }
+//~^ ERROR missing lifetime specifier
+fn func2<'a>(_arg: &Thing<'a>) -> &() { unimplemented!() }
+//~^ ERROR missing lifetime specifier
+
+fn main() {}
diff --git a/src/test/ui/suggestions/return-without-lifetime.stderr b/src/test/ui/suggestions/return-without-lifetime.stderr
new file mode 100644
index 0000000000000..72f1c142d028f
--- /dev/null
+++ b/src/test/ui/suggestions/return-without-lifetime.stderr
@@ -0,0 +1,19 @@
+error[E0106]: missing lifetime specifier
+ --> $DIR/return-without-lifetime.rs:3:34
+ |
+LL | fn func1<'a>(_arg: &'a Thing) -> &() { unimplemented!() }
+ | ^ help: consider using the named lifetime `'a`: `&'a`
+ |
+ = help: this function's return type contains a borrowed value, but the signature does not say which one of `_arg`'s 2 lifetimes it is borrowed from
+
+error[E0106]: missing lifetime specifier
+ --> $DIR/return-without-lifetime.rs:5:35
+ |
+LL | fn func2<'a>(_arg: &Thing<'a>) -> &() { unimplemented!() }
+ | ^ help: consider using the named lifetime `'a`: `&'a`
+ |
+ = help: this function's return type contains a borrowed value, but the signature does not say which one of `_arg`'s 2 lifetimes it is borrowed from
+
+error: aborting due to 2 previous errors
+
+For more information about this error, try `rustc --explain E0106`.
From f9234767e4ff9b682437464efc9a6ff59db4cff9 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Esteban=20K=C3=BCber?= <esteban@kuber.com.ar>
Date: Tue, 12 Mar 2019 15:34:16 -0700
Subject: [PATCH 2/3] review comments
---
src/librustc/middle/resolve_lifetime.rs | 2 +-
src/test/ui/suggestions/return-without-lifetime.stderr | 4 ++--
2 files changed, 3 insertions(+), 3 deletions(-)
diff --git a/src/librustc/middle/resolve_lifetime.rs b/src/librustc/middle/resolve_lifetime.rs
index 35bca04d1e623..d03268df5e148 100644
--- a/src/librustc/middle/resolve_lifetime.rs
+++ b/src/librustc/middle/resolve_lifetime.rs
@@ -2912,7 +2912,7 @@ fn add_missing_lifetime_specifiers_label(
) {
err.span_suggestion(
span,
- &format!("consider using the named lifetime `{}`", name),
+ "consider using the named lifetime",
format!("&{} ", name),
Applicability::MaybeIncorrect,
);
diff --git a/src/test/ui/suggestions/return-without-lifetime.stderr b/src/test/ui/suggestions/return-without-lifetime.stderr
index 72f1c142d028f..1ffe91bce05a5 100644
--- a/src/test/ui/suggestions/return-without-lifetime.stderr
+++ b/src/test/ui/suggestions/return-without-lifetime.stderr
@@ -2,7 +2,7 @@ error[E0106]: missing lifetime specifier
--> $DIR/return-without-lifetime.rs:3:34
|
LL | fn func1<'a>(_arg: &'a Thing) -> &() { unimplemented!() }
- | ^ help: consider using the named lifetime `'a`: `&'a`
+ | ^ help: consider using the named lifetime: `&'a`
|
= help: this function's return type contains a borrowed value, but the signature does not say which one of `_arg`'s 2 lifetimes it is borrowed from
@@ -10,7 +10,7 @@ error[E0106]: missing lifetime specifier
--> $DIR/return-without-lifetime.rs:5:35
|
LL | fn func2<'a>(_arg: &Thing<'a>) -> &() { unimplemented!() }
- | ^ help: consider using the named lifetime `'a`: `&'a`
+ | ^ help: consider using the named lifetime: `&'a`
|
= help: this function's return type contains a borrowed value, but the signature does not say which one of `_arg`'s 2 lifetimes it is borrowed from
From 0ea9b58029bc7c3da3f213eb9e39acdefcf12647 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Esteban=20K=C3=BCber?= <esteban@kuber.com.ar>
Date: Tue, 12 Mar 2019 18:18:24 -0700
Subject: [PATCH 3/3] Suggest adding lifetime to struct field
---
src/librustc/middle/resolve_lifetime.rs | 9 ++++++++-
src/test/ui/suggestions/return-without-lifetime.rs | 2 ++
.../ui/suggestions/return-without-lifetime.stderr | 12 +++++++++---
3 files changed, 19 insertions(+), 4 deletions(-)
diff --git a/src/librustc/middle/resolve_lifetime.rs b/src/librustc/middle/resolve_lifetime.rs
index d03268df5e148..c9ff84ab2f08a 100644
--- a/src/librustc/middle/resolve_lifetime.rs
+++ b/src/librustc/middle/resolve_lifetime.rs
@@ -2306,7 +2306,13 @@ impl<'a, 'tcx> LifetimeContext<'a, 'tcx> {
Scope::Root => break None,
- Scope::Binder { s, .. } => {
+ Scope::Binder { s, ref lifetimes, .. } => {
+ // collect named lifetimes for suggestions
+ for name in lifetimes.keys() {
+ if let hir::ParamName::Plain(name) = name {
+ lifetime_names.insert(*name);
+ }
+ }
late_depth += 1;
scope = s;
}
@@ -2323,6 +2329,7 @@ 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);
diff --git a/src/test/ui/suggestions/return-without-lifetime.rs b/src/test/ui/suggestions/return-without-lifetime.rs
index 5f19e93013acf..9bfce11be9ea3 100644
--- a/src/test/ui/suggestions/return-without-lifetime.rs
+++ b/src/test/ui/suggestions/return-without-lifetime.rs
@@ -1,4 +1,6 @@
struct Thing<'a>(&'a ());
+struct Foo<'a>(&usize);
+//~^ ERROR missing lifetime specifier
fn func1<'a>(_arg: &'a Thing) -> &() { unimplemented!() }
//~^ ERROR missing lifetime specifier
diff --git a/src/test/ui/suggestions/return-without-lifetime.stderr b/src/test/ui/suggestions/return-without-lifetime.stderr
index 1ffe91bce05a5..7f5ff95938e30 100644
--- a/src/test/ui/suggestions/return-without-lifetime.stderr
+++ b/src/test/ui/suggestions/return-without-lifetime.stderr
@@ -1,5 +1,11 @@
error[E0106]: missing lifetime specifier
- --> $DIR/return-without-lifetime.rs:3:34
+ --> $DIR/return-without-lifetime.rs:2:16
+ |
+LL | struct Foo<'a>(&usize);
+ | ^ help: consider using the named lifetime: `&'a`
+
+error[E0106]: missing lifetime specifier
+ --> $DIR/return-without-lifetime.rs:5:34
|
LL | fn func1<'a>(_arg: &'a Thing) -> &() { unimplemented!() }
| ^ help: consider using the named lifetime: `&'a`
@@ -7,13 +13,13 @@ LL | fn func1<'a>(_arg: &'a Thing) -> &() { unimplemented!() }
= help: this function's return type contains a borrowed value, but the signature does not say which one of `_arg`'s 2 lifetimes it is borrowed from
error[E0106]: missing lifetime specifier
- --> $DIR/return-without-lifetime.rs:5:35
+ --> $DIR/return-without-lifetime.rs:7:35
|
LL | fn func2<'a>(_arg: &Thing<'a>) -> &() { unimplemented!() }
| ^ help: consider using the named lifetime: `&'a`
|
= help: this function's return type contains a borrowed value, but the signature does not say which one of `_arg`'s 2 lifetimes it is borrowed from
-error: aborting due to 2 previous errors
+error: aborting due to 3 previous errors
For more information about this error, try `rustc --explain E0106`.