diff --git a/src/librustc/middle/resolve_lifetime.rs b/src/librustc/middle/resolve_lifetime.rs
index 361abb1689619..31e34895052a3 100644
--- a/src/librustc/middle/resolve_lifetime.rs
+++ b/src/librustc/middle/resolve_lifetime.rs
@@ -1443,23 +1443,101 @@ impl<'a, 'tcx> LifetimeContext<'a, 'tcx> {
/// helper method to determine the span to remove when suggesting the
/// deletion of a lifetime
fn lifetime_deletion_span(&self, name: ast::Ident, generics: &hir::Generics) -> Option<Span> {
- if generics.params.len() == 1 {
- // if sole lifetime, remove the `<>` brackets
- Some(generics.span)
- } else {
- generics.params.iter().enumerate().find_map(|(i, param)| {
- if param.name.ident() == name {
- // We also want to delete a leading or trailing comma
- // as appropriate
- if i >= generics.params.len() - 1 {
- Some(generics.params[i - 1].span.shrink_to_hi().to(param.span))
- } else {
- Some(param.span.to(generics.params[i + 1].span.shrink_to_lo()))
+ generics.params.iter().enumerate().find_map(|(i, param)| {
+ if param.name.ident() == name {
+ let mut in_band = false;
+ if let hir::GenericParamKind::Lifetime { kind } = param.kind {
+ if let hir::LifetimeParamKind::InBand = kind {
+ in_band = true;
}
+ }
+ if in_band {
+ Some(param.span)
} else {
- None
+ if generics.params.len() == 1 {
+ // if sole lifetime, remove the entire `<>` brackets
+ Some(generics.span)
+ } else {
+ // if removing within `<>` brackets, we also want to
+ // delete a leading or trailing comma as appropriate
+ if i >= generics.params.len() - 1 {
+ Some(generics.params[i - 1].span.shrink_to_hi().to(param.span))
+ } else {
+ Some(param.span.to(generics.params[i + 1].span.shrink_to_lo()))
+ }
+ }
}
- })
+ } else {
+ None
+ }
+ })
+ }
+
+ // helper method to issue suggestions from `fn rah<'a>(&'a T)` to `fn rah(&T)`
+ fn suggest_eliding_single_use_lifetime(
+ &self, err: &mut DiagnosticBuilder<'_>, def_id: DefId, lifetime: &hir::Lifetime
+ ) {
+ // FIXME: future work: also suggest `impl Foo<'_>` for `impl<'a> Foo<'a>`
+ let name = lifetime.name.ident();
+ let mut remove_decl = None;
+ if let Some(parent_def_id) = self.tcx.parent(def_id) {
+ if let Some(generics) = self.tcx.hir.get_generics(parent_def_id) {
+ remove_decl = self.lifetime_deletion_span(name, generics);
+ }
+ }
+
+ let mut remove_use = None;
+ let mut find_arg_use_span = |inputs: &hir::HirVec<hir::Ty>| {
+ for input in inputs {
+ if let hir::TyKind::Rptr(lt, _) = input.node {
+ if lt.name.ident() == name {
+ // include the trailing whitespace between the ampersand and the type name
+ let lt_through_ty_span = lifetime.span.to(input.span.shrink_to_hi());
+ remove_use = Some(
+ self.tcx.sess.source_map()
+ .span_until_non_whitespace(lt_through_ty_span)
+ );
+ break;
+ }
+ }
+ }
+ };
+ if let Node::Lifetime(hir_lifetime) = self.tcx.hir.get(lifetime.id) {
+ if let Some(parent) = self.tcx.hir.find(self.tcx.hir.get_parent(hir_lifetime.id)) {
+ match parent {
+ Node::Item(item) => {
+ if let hir::ItemKind::Fn(decl, _, _, _) = &item.node {
+ find_arg_use_span(&decl.inputs);
+ }
+ },
+ Node::ImplItem(impl_item) => {
+ if let hir::ImplItemKind::Method(sig, _) = &impl_item.node {
+ find_arg_use_span(&sig.decl.inputs);
+ }
+ }
+ _ => {}
+ }
+ }
+ }
+
+ if let (Some(decl_span), Some(use_span)) = (remove_decl, remove_use) {
+ // if both declaration and use deletion spans start at the same
+ // place ("start at" because the latter includes trailing
+ // whitespace), then this is an in-band lifetime
+ if decl_span.shrink_to_lo() == use_span.shrink_to_lo() {
+ err.span_suggestion_with_applicability(
+ use_span,
+ "elide the single-use lifetime",
+ String::new(),
+ Applicability::MachineApplicable,
+ );
+ } else {
+ err.multipart_suggestion_with_applicability(
+ "elide the single-use lifetime",
+ vec![(decl_span, String::new()), (use_span, String::new())],
+ Applicability::MachineApplicable,
+ );
+ }
}
}
@@ -1515,14 +1593,26 @@ impl<'a, 'tcx> LifetimeContext<'a, 'tcx> {
_ => None,
} {
debug!("id = {:?} span = {:?} name = {:?}", node_id, span, name);
+
+ if name == keywords::UnderscoreLifetime.ident() {
+ continue;
+ }
+
let mut err = self.tcx.struct_span_lint_node(
lint::builtin::SINGLE_USE_LIFETIMES,
id,
span,
&format!("lifetime parameter `{}` only used once", name),
);
- err.span_label(span, "this lifetime...");
- err.span_label(lifetime.span, "...is used only here");
+
+ if span == lifetime.span {
+ // spans are the same for in-band lifetime declarations
+ err.span_label(span, "this lifetime is only used here");
+ } else {
+ err.span_label(span, "this lifetime...");
+ err.span_label(lifetime.span, "...is used only here");
+ }
+ self.suggest_eliding_single_use_lifetime(&mut err, def_id, lifetime);
err.emit();
}
}
@@ -1555,7 +1645,7 @@ impl<'a, 'tcx> LifetimeContext<'a, 'tcx> {
if let Some(span) = unused_lt_span {
err.span_suggestion_with_applicability(
span,
- "remove it",
+ "elide the unused lifetime",
String::new(),
Applicability::MachineApplicable,
);
diff --git a/src/test/ui/single-use-lifetime/one-use-in-fn-argument-in-band.fixed b/src/test/ui/single-use-lifetime/one-use-in-fn-argument-in-band.fixed
new file mode 100644
index 0000000000000..fd9b10e1a32ea
--- /dev/null
+++ b/src/test/ui/single-use-lifetime/one-use-in-fn-argument-in-band.fixed
@@ -0,0 +1,28 @@
+// Copyright 2016 The Rust Project Developers. See the COPYRIGHT
+// file at the top-level directory of this distribution and at
+// http://rust-lang.org/COPYRIGHT.
+//
+// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
+// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
+// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
+// option. This file may not be copied, modified, or distributed
+// except according to those terms.
+
+// run-rustfix
+
+#![feature(in_band_lifetimes)]
+#![deny(single_use_lifetimes)]
+#![allow(dead_code)]
+#![allow(unused_variables)]
+
+// Test that we DO warn when lifetime name is used only
+// once in a fn argument, even with in band lifetimes.
+
+fn a(x: &u32, y: &u32) {
+ //~^ ERROR `'a` only used once
+ //~| ERROR `'b` only used once
+ //~| HELP elide the single-use lifetime
+ //~| HELP elide the single-use lifetime
+}
+
+fn main() { }
diff --git a/src/test/ui/single-use-lifetime/one-use-in-fn-argument-in-band.rs b/src/test/ui/single-use-lifetime/one-use-in-fn-argument-in-band.rs
index 1aad3265cbe0a..0d5f65e6d1b53 100644
--- a/src/test/ui/single-use-lifetime/one-use-in-fn-argument-in-band.rs
+++ b/src/test/ui/single-use-lifetime/one-use-in-fn-argument-in-band.rs
@@ -8,6 +8,8 @@
// option. This file may not be copied, modified, or distributed
// except according to those terms.
+// run-rustfix
+
#![feature(in_band_lifetimes)]
#![deny(single_use_lifetimes)]
#![allow(dead_code)]
@@ -19,6 +21,8 @@
fn a(x: &'a u32, y: &'b u32) {
//~^ ERROR `'a` only used once
//~| ERROR `'b` only used once
+ //~| HELP elide the single-use lifetime
+ //~| HELP elide the single-use lifetime
}
fn main() { }
diff --git a/src/test/ui/single-use-lifetime/one-use-in-fn-argument-in-band.stderr b/src/test/ui/single-use-lifetime/one-use-in-fn-argument-in-band.stderr
index 6d18075ba37cf..a9f8411d41103 100644
--- a/src/test/ui/single-use-lifetime/one-use-in-fn-argument-in-band.stderr
+++ b/src/test/ui/single-use-lifetime/one-use-in-fn-argument-in-band.stderr
@@ -1,26 +1,26 @@
error: lifetime parameter `'a` only used once
- --> $DIR/one-use-in-fn-argument-in-band.rs:19:10
+ --> $DIR/one-use-in-fn-argument-in-band.rs:21:10
|
LL | fn a(x: &'a u32, y: &'b u32) {
- | ^^
+ | ^^-
| |
- | this lifetime...
- | ...is used only here
+ | this lifetime is only used here
+ | help: elide the single-use lifetime
|
note: lint level defined here
- --> $DIR/one-use-in-fn-argument-in-band.rs:12:9
+ --> $DIR/one-use-in-fn-argument-in-band.rs:14:9
|
LL | #![deny(single_use_lifetimes)]
| ^^^^^^^^^^^^^^^^^^^^
error: lifetime parameter `'b` only used once
- --> $DIR/one-use-in-fn-argument-in-band.rs:19:22
+ --> $DIR/one-use-in-fn-argument-in-band.rs:21:22
|
LL | fn a(x: &'a u32, y: &'b u32) {
- | ^^
+ | ^^-
| |
- | this lifetime...
- | ...is used only here
+ | this lifetime is only used here
+ | help: elide the single-use lifetime
error: aborting due to 2 previous errors
diff --git a/src/test/ui/single-use-lifetime/one-use-in-fn-argument.rs b/src/test/ui/single-use-lifetime/one-use-in-fn-argument.rs
index 9ac813a24ded3..a1b8866c8c455 100644
--- a/src/test/ui/single-use-lifetime/one-use-in-fn-argument.rs
+++ b/src/test/ui/single-use-lifetime/one-use-in-fn-argument.rs
@@ -16,6 +16,7 @@
// once in a fn argument.
fn a<'a>(x: &'a u32) { //~ ERROR `'a` only used once
+ //~^ HELP elide the single-use lifetime
}
fn main() { }
diff --git a/src/test/ui/single-use-lifetime/one-use-in-fn-argument.stderr b/src/test/ui/single-use-lifetime/one-use-in-fn-argument.stderr
index 4c13133581bb4..0a23ecaf458ad 100644
--- a/src/test/ui/single-use-lifetime/one-use-in-fn-argument.stderr
+++ b/src/test/ui/single-use-lifetime/one-use-in-fn-argument.stderr
@@ -11,6 +11,10 @@ note: lint level defined here
|
LL | #![deny(single_use_lifetimes)]
| ^^^^^^^^^^^^^^^^^^^^
+help: elide the single-use lifetime
+ |
+LL | fn a(x: &u32) { //~ ERROR `'a` only used once
+ | -- --
error: aborting due to previous error
diff --git a/src/test/ui/single-use-lifetime/one-use-in-inherent-impl-header.rs b/src/test/ui/single-use-lifetime/one-use-in-inherent-impl-header.rs
index a862bbbe30c09..b392f7a51746f 100644
--- a/src/test/ui/single-use-lifetime/one-use-in-inherent-impl-header.rs
+++ b/src/test/ui/single-use-lifetime/one-use-in-inherent-impl-header.rs
@@ -12,10 +12,8 @@
#![allow(dead_code)]
#![allow(unused_variables)]
-// Test that we DO warn for a lifetime used only once in an impl.
-//
-// (Actually, until #15872 is fixed, you can't use `'_` here, but
-// hopefully that will come soon.)
+// Test that we DO warn for a lifetime used only once in an impl, and that we
+// don't warn for the anonymous lifetime.
struct Foo<'f> {
data: &'f u32
@@ -26,4 +24,9 @@ impl<'f> Foo<'f> { //~ ERROR `'f` only used once
}
}
+impl Foo<'_> {
+ fn inherent_b(&self) {}
+}
+
+
fn main() { }
diff --git a/src/test/ui/single-use-lifetime/one-use-in-inherent-impl-header.stderr b/src/test/ui/single-use-lifetime/one-use-in-inherent-impl-header.stderr
index 2509366f9696f..40dfa677d0ab2 100644
--- a/src/test/ui/single-use-lifetime/one-use-in-inherent-impl-header.stderr
+++ b/src/test/ui/single-use-lifetime/one-use-in-inherent-impl-header.stderr
@@ -1,5 +1,5 @@
error: lifetime parameter `'f` only used once
- --> $DIR/one-use-in-inherent-impl-header.rs:24:6
+ --> $DIR/one-use-in-inherent-impl-header.rs:22:6
|
LL | impl<'f> Foo<'f> { //~ ERROR `'f` only used once
| ^^ -- ...is used only here
diff --git a/src/test/ui/single-use-lifetime/one-use-in-inherent-method-argument.rs b/src/test/ui/single-use-lifetime/one-use-in-inherent-method-argument.rs
index 863d8faef6ea1..63c3bbdfe4a11 100644
--- a/src/test/ui/single-use-lifetime/one-use-in-inherent-method-argument.rs
+++ b/src/test/ui/single-use-lifetime/one-use-in-inherent-method-argument.rs
@@ -20,6 +20,7 @@ struct Foo<'f> {
impl<'f> Foo<'f> { //~ ERROR `'f` only used once
fn inherent_a<'a>(&self, data: &'a u32) { //~ ERROR `'a` only used once
+ //~^ HELP elide the single-use lifetime
}
}
diff --git a/src/test/ui/single-use-lifetime/one-use-in-inherent-method-argument.stderr b/src/test/ui/single-use-lifetime/one-use-in-inherent-method-argument.stderr
index cfc8dbf18dc01..d0651a437b091 100644
--- a/src/test/ui/single-use-lifetime/one-use-in-inherent-method-argument.stderr
+++ b/src/test/ui/single-use-lifetime/one-use-in-inherent-method-argument.stderr
@@ -11,6 +11,10 @@ note: lint level defined here
|
LL | #![deny(single_use_lifetimes)]
| ^^^^^^^^^^^^^^^^^^^^
+help: elide the single-use lifetime
+ |
+LL | fn inherent_a(&self, data: &u32) { //~ ERROR `'a` only used once
+ | -- --
error: lifetime parameter `'f` only used once
--> $DIR/one-use-in-inherent-method-argument.rs:21:6
diff --git a/src/test/ui/single-use-lifetime/one-use-in-trait-method-argument.rs b/src/test/ui/single-use-lifetime/one-use-in-trait-method-argument.rs
index 389ba5c873ad8..c36e9ef2b2237 100644
--- a/src/test/ui/single-use-lifetime/one-use-in-trait-method-argument.rs
+++ b/src/test/ui/single-use-lifetime/one-use-in-trait-method-argument.rs
@@ -23,6 +23,7 @@ impl<'f> Iterator for Foo<'f> {
type Item = &'f u32;
fn next<'g>(&'g mut self) -> Option<Self::Item> { //~ ERROR `'g` only used once
+ //~^ HELP elide the single-use lifetime
None
}
}
diff --git a/src/test/ui/single-use-lifetime/one-use-in-trait-method-argument.stderr b/src/test/ui/single-use-lifetime/one-use-in-trait-method-argument.stderr
index 4a796d83242fd..e054d0ad9349b 100644
--- a/src/test/ui/single-use-lifetime/one-use-in-trait-method-argument.stderr
+++ b/src/test/ui/single-use-lifetime/one-use-in-trait-method-argument.stderr
@@ -11,6 +11,10 @@ note: lint level defined here
|
LL | #![deny(single_use_lifetimes)]
| ^^^^^^^^^^^^^^^^^^^^
+help: elide the single-use lifetime
+ |
+LL | fn next(&mut self) -> Option<Self::Item> { //~ ERROR `'g` only used once
+ | ----
error: aborting due to previous error
diff --git a/src/test/ui/single-use-lifetime/zero-uses-in-fn.fixed b/src/test/ui/single-use-lifetime/zero-uses-in-fn.fixed
index 5ba7df8a1e61f..89607af260a52 100644
--- a/src/test/ui/single-use-lifetime/zero-uses-in-fn.fixed
+++ b/src/test/ui/single-use-lifetime/zero-uses-in-fn.fixed
@@ -7,17 +7,17 @@
fn september() {}
//~^ ERROR lifetime parameter `'a` never used
-//~| HELP remove it
+//~| HELP elide the unused lifetime
fn october<'b, T>(s: &'b T) -> &'b T {
//~^ ERROR lifetime parameter `'a` never used
- //~| HELP remove it
+ //~| HELP elide the unused lifetime
s
}
fn november<'a>(s: &'a str) -> (&'a str) {
//~^ ERROR lifetime parameter `'b` never used
- //~| HELP remove it
+ //~| HELP elide the unused lifetime
s
}
diff --git a/src/test/ui/single-use-lifetime/zero-uses-in-fn.rs b/src/test/ui/single-use-lifetime/zero-uses-in-fn.rs
index a56d7fa8abc02..be0bdb9b62851 100644
--- a/src/test/ui/single-use-lifetime/zero-uses-in-fn.rs
+++ b/src/test/ui/single-use-lifetime/zero-uses-in-fn.rs
@@ -7,17 +7,17 @@
fn september<'a>() {}
//~^ ERROR lifetime parameter `'a` never used
-//~| HELP remove it
+//~| HELP elide the unused lifetime
fn october<'a, 'b, T>(s: &'b T) -> &'b T {
//~^ ERROR lifetime parameter `'a` never used
- //~| HELP remove it
+ //~| HELP elide the unused lifetime
s
}
fn november<'a, 'b>(s: &'a str) -> (&'a str) {
//~^ ERROR lifetime parameter `'b` never used
- //~| HELP remove it
+ //~| HELP elide the unused lifetime
s
}
diff --git a/src/test/ui/single-use-lifetime/zero-uses-in-fn.stderr b/src/test/ui/single-use-lifetime/zero-uses-in-fn.stderr
index 566c841cfa969..2ccba796d4229 100644
--- a/src/test/ui/single-use-lifetime/zero-uses-in-fn.stderr
+++ b/src/test/ui/single-use-lifetime/zero-uses-in-fn.stderr
@@ -2,7 +2,7 @@ error: lifetime parameter `'a` never used
--> $DIR/zero-uses-in-fn.rs:8:14
|
LL | fn september<'a>() {}
- | -^^- help: remove it
+ | -^^- help: elide the unused lifetime
|
note: lint level defined here
--> $DIR/zero-uses-in-fn.rs:5:9
@@ -16,7 +16,7 @@ error: lifetime parameter `'a` never used
LL | fn october<'a, 'b, T>(s: &'b T) -> &'b T {
| ^^--
| |
- | help: remove it
+ | help: elide the unused lifetime
error: lifetime parameter `'b` never used
--> $DIR/zero-uses-in-fn.rs:18:17
@@ -24,7 +24,7 @@ error: lifetime parameter `'b` never used
LL | fn november<'a, 'b>(s: &'a str) -> (&'a str) {
| --^^
| |
- | help: remove it
+ | help: elide the unused lifetime
error: aborting due to 3 previous errors
diff --git a/src/test/ui/single-use-lifetime/zero-uses-in-impl.stderr b/src/test/ui/single-use-lifetime/zero-uses-in-impl.stderr
index 1b77ebdec99c6..3f9d907ade679 100644
--- a/src/test/ui/single-use-lifetime/zero-uses-in-impl.stderr
+++ b/src/test/ui/single-use-lifetime/zero-uses-in-impl.stderr
@@ -2,7 +2,7 @@ error: lifetime parameter `'a` never used
--> $DIR/zero-uses-in-impl.rs:8:6
|
LL | impl<'a> Foo {} //~ ERROR `'a` never used
- | -^^- help: remove it
+ | -^^- help: elide the unused lifetime
|
note: lint level defined here
--> $DIR/zero-uses-in-impl.rs:3:9