diff options
| -rw-r--r-- | src/librustc/middle/resolve_lifetime.rs | 37 | ||||
| -rw-r--r-- | src/test/ui/suggestions/return-without-lifetime.rs | 8 | ||||
| -rw-r--r-- | src/test/ui/suggestions/return-without-lifetime.stderr | 19 |
3 files changed, 60 insertions, 4 deletions
diff --git a/src/librustc/middle/resolve_lifetime.rs b/src/librustc/middle/resolve_lifetime.rs index f862b690f88..35bca04d1e6 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 00000000000..5f19e93013a --- /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 00000000000..72f1c142d02 --- /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`. |