diff options
6 files changed, 172 insertions, 20 deletions
diff --git a/src/librustc_resolve/late/diagnostics.rs b/src/librustc_resolve/late/diagnostics.rs index e9c463c7a3e..5b8d8dd0635 100644 --- a/src/librustc_resolve/late/diagnostics.rs +++ b/src/librustc_resolve/late/diagnostics.rs @@ -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(<))) + .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(<_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(<_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. diff --git a/src/librustc_resolve/late/lifetimes.rs b/src/librustc_resolve/late/lifetimes.rs index 6cb92843766..e5accc7fde9 100644 --- a/src/librustc_resolve/late/lifetimes.rs +++ b/src/librustc_resolve/late/lifetimes.rs @@ -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(); diff --git a/src/test/ui/associated-types/bound-lifetime-in-binding-only.elision.stderr b/src/test/ui/associated-types/bound-lifetime-in-binding-only.elision.stderr index 00f44129cc8..6c68cc7bc61 100644 --- a/src/test/ui/associated-types/bound-lifetime-in-binding-only.elision.stderr +++ b/src/test/ui/associated-types/bound-lifetime-in-binding-only.elision.stderr @@ -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>() { diff --git a/src/test/ui/associated-types/bound-lifetime-in-return-only.elision.stderr b/src/test/ui/associated-types/bound-lifetime-in-return-only.elision.stderr index a5242707c71..93d2f8e7911 100644 --- a/src/test/ui/associated-types/bound-lifetime-in-return-only.elision.stderr +++ b/src/test/ui/associated-types/bound-lifetime-in-return-only.elision.stderr @@ -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) { diff --git a/src/test/ui/suggestions/missing-lt-for-hrtb.rs b/src/test/ui/suggestions/missing-lt-for-hrtb.rs new file mode 100644 index 00000000000..a90a90122ad --- /dev/null +++ b/src/test/ui/suggestions/missing-lt-for-hrtb.rs @@ -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(&())); +} diff --git a/src/test/ui/suggestions/missing-lt-for-hrtb.stderr b/src/test/ui/suggestions/missing-lt-for-hrtb.stderr new file mode 100644 index 00000000000..2cb63500e48 --- /dev/null +++ b/src/test/ui/suggestions/missing-lt-for-hrtb.stderr @@ -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`. |