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Suggest adding a new lifetime parameter when two elided lifetimes sho…
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…uld match up for traits and impls.

Issue #94462
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@kckeiks
kckeiks committed Feb 28, 2022
1 parent 97cde9f commit abcccc9
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Showing 11 changed files with 258 additions and 52 deletions.
100 changes: 48 additions & 52 deletions compiler/rustc_infer/src/infer/error_reporting/nice_region_error/different_lifetimes.rs
View file
Expand Up @@ -166,59 +166,55 @@ impl<'a, 'tcx> NiceRegionError<'a, 'tcx> {
if lifetime_sub.name.is_elided() && lifetime_sup.name.is_elided() {
if let Some(anon_reg) = self.tcx().is_suitable_region(sub) {
let hir_id = self.tcx().hir().local_def_id_to_hir_id(anon_reg.def_id);
if let hir::Node::Item(&hir::Item {
kind: hir::ItemKind::Fn(_, ref generics, ..),
..
}) = self.tcx().hir().get(hir_id)
{
let (suggestion_param_name, introduce_new) = generics
.params
.iter()
.find(|p| matches!(p.kind, GenericParamKind::Lifetime { .. }))
.and_then(|p| self.tcx().sess.source_map().span_to_snippet(p.span).ok())
.map(|name| (name, false))
.unwrap_or_else(|| ("'a".to_string(), true));

let mut suggestions = vec![
if let hir::LifetimeName::Underscore = lifetime_sub.name {
(lifetime_sub.span, suggestion_param_name.clone())
} else {
(
lifetime_sub.span.shrink_to_hi(),
suggestion_param_name.clone() + " ",
)
},
if let hir::LifetimeName::Underscore = lifetime_sup.name {
(lifetime_sup.span, suggestion_param_name.clone())
} else {
(
lifetime_sup.span.shrink_to_hi(),
suggestion_param_name.clone() + " ",
)
},
];

if introduce_new {
let new_param_suggestion = match &generics.params {
[] => (generics.span, format!("<{}>", suggestion_param_name)),
[first, ..] => (
first.span.shrink_to_lo(),
format!("{}, ", suggestion_param_name),
),
};

suggestions.push(new_param_suggestion);
}

err.multipart_suggestion(
"consider introducing a named lifetime parameter",
suggestions,
Applicability::MaybeIncorrect,
);
err.note(
"each elided lifetime in input position becomes a distinct lifetime",
);

let generics = match self.tcx().hir().get(hir_id) {
hir::Node::Item(&hir::Item {
kind: hir::ItemKind::Fn(_, ref generics, ..),
..
})
| hir::Node::TraitItem(&hir::TraitItem { ref generics, .. })
| hir::Node::ImplItem(&hir::ImplItem { ref generics, .. }) => generics,
_ => return,
};

let (suggestion_param_name, introduce_new) = generics
.params
.iter()
.find(|p| matches!(p.kind, GenericParamKind::Lifetime { .. }))
.and_then(|p| self.tcx().sess.source_map().span_to_snippet(p.span).ok())
.map(|name| (name, false))
.unwrap_or_else(|| ("'a".to_string(), true));

let mut suggestions = vec![
if let hir::LifetimeName::Underscore = lifetime_sub.name {
(lifetime_sub.span, suggestion_param_name.clone())
} else {
(lifetime_sub.span.shrink_to_hi(), suggestion_param_name.clone() + " ")
},
if let hir::LifetimeName::Underscore = lifetime_sup.name {
(lifetime_sup.span, suggestion_param_name.clone())
} else {
(lifetime_sup.span.shrink_to_hi(), suggestion_param_name.clone() + " ")
},
];

if introduce_new {
let new_param_suggestion = match &generics.params {
[] => (generics.span, format!("<{}>", suggestion_param_name)),
[first, ..] => {
(first.span.shrink_to_lo(), format!("{}, ", suggestion_param_name))
}
};

suggestions.push(new_param_suggestion);
}

err.multipart_suggestion(
"consider introducing a named lifetime parameter",
suggestions,
Applicability::MaybeIncorrect,
);
err.note("each elided lifetime in input position becomes a distinct lifetime");
}
}
}
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6 changes: 6 additions & 0 deletions src/test/ui/issues/issue-17728.stderr
View file
Expand Up @@ -8,6 +8,12 @@ LL | fn attemptTraverse(&self, room: &Room, directionStr: &str) -> Result<&R
...
LL | Some(entry) => Ok(entry),
| ^^^^^^^^^ ...but data from `room` is returned here
|
= note: each elided lifetime in input position becomes a distinct lifetime
help: consider introducing a named lifetime parameter
|
LL | fn attemptTraverse<'a>(&'a self, room: &'a Room, directionStr: &str) -> Result<&Room, &str> {
| ++++ ++ ++

error[E0308]: `match` arms have incompatible types
--> $DIR/issue-17728.rs:109:14
Expand Down
6 changes: 6 additions & 0 deletions src/test/ui/lifetimes/lifetime-errors/ex3-both-anon-regions-return-type-is-anon.stderr
View file
Expand Up @@ -7,6 +7,12 @@ LL | fn foo<'a>(&self, x: &i32) -> &i32 {
| this parameter and the return type are declared with different lifetimes...
LL | x
| ^ ...but data from `x` is returned here
|
= note: each elided lifetime in input position becomes a distinct lifetime
help: consider introducing a named lifetime parameter
|
LL | fn foo<'a>(&'a self, x: &'a i32) -> &i32 {
| ++ ++

error: aborting due to previous error

Expand Down
6 changes: 6 additions & 0 deletions src/test/ui/lifetimes/lifetime-errors/ex3-both-anon-regions-self-is-anon.stderr
View file
Expand Up @@ -7,6 +7,12 @@ LL | fn foo<'a>(&self, x: &Foo) -> &Foo {
| this parameter and the return type are declared with different lifetimes...
LL | if true { x } else { self }
| ^ ...but data from `x` is returned here
|
= note: each elided lifetime in input position becomes a distinct lifetime
help: consider introducing a named lifetime parameter
|
LL | fn foo<'a>(&'a self, x: &'a Foo) -> &Foo {
| ++ ++

error: aborting due to previous error

Expand Down
6 changes: 6 additions & 0 deletions src/test/ui/lifetimes/lifetime-errors/ex3-both-anon-regions-using-impl-items.stderr
View file
Expand Up @@ -5,6 +5,12 @@ LL | fn foo(x: &mut Vec<&u8>, y: &u8) {
| --- --- these two types are declared with different lifetimes...
LL | x.push(y);
| ^ ...but data from `y` flows into `x` here
|
= note: each elided lifetime in input position becomes a distinct lifetime
help: consider introducing a named lifetime parameter
|
LL | fn foo<'a>(x: &mut Vec<&'a u8>, y: &'a u8) {
| ++++ ++ ++

error: aborting due to previous error

Expand Down
12 changes: 12 additions & 0 deletions src/test/ui/self/arbitrary_self_types_pin_lifetime_mismatch.stderr
View file
Expand Up @@ -5,6 +5,12 @@ LL | fn a(self: Pin<&Foo>, f: &Foo) -> &Foo { f }
| ---- ---- ^ ...but data from `f` is returned here
| |
| this parameter and the return type are declared with different lifetimes...
|
= note: each elided lifetime in input position becomes a distinct lifetime
help: consider introducing a named lifetime parameter
|
LL | fn a<'a>(self: Pin<&'a Foo>, f: &'a Foo) -> &Foo { f }
| ++++ ++ ++

error[E0623]: lifetime mismatch
--> $DIR/arbitrary_self_types_pin_lifetime_mismatch.rs:8:76
Expand All @@ -13,6 +19,12 @@ LL | fn c(self: Pin<&Self>, f: &Foo, g: &Foo) -> (Pin<&Foo>, &Foo) { (self,
| ---- ----------------- ^ ...but data from `f` is returned here
| |
| this parameter and the return type are declared with different lifetimes...
|
= note: each elided lifetime in input position becomes a distinct lifetime
help: consider introducing a named lifetime parameter
|
LL | fn c<'a>(self: Pin<&'a Self>, f: &'a Foo, g: &Foo) -> (Pin<&Foo>, &Foo) { (self, f) }
| ++++ ++ ++

error[E0623]: lifetime mismatch
--> $DIR/arbitrary_self_types_pin_lifetime_mismatch.rs:13:58
Expand Down
36 changes: 36 additions & 0 deletions src/test/ui/self/elision/lt-ref-self.stderr
View file
Expand Up @@ -7,6 +7,12 @@ LL | fn ref_self(&self, f: &u32) -> &u32 {
| this parameter and the return type are declared with different lifetimes...
LL | f
| ^ ...but data from `f` is returned here
|
= note: each elided lifetime in input position becomes a distinct lifetime
help: consider introducing a named lifetime parameter
|
LL | fn ref_self<'a>(&'a self, f: &'a u32) -> &u32 {
| ++++ ++ ++

error[E0623]: lifetime mismatch
--> $DIR/lt-ref-self.rs:17:9
Expand All @@ -17,6 +23,12 @@ LL | fn ref_Self(self: &Self, f: &u32) -> &u32 {
| this parameter and the return type are declared with different lifetimes...
LL | f
| ^ ...but data from `f` is returned here
|
= note: each elided lifetime in input position becomes a distinct lifetime
help: consider introducing a named lifetime parameter
|
LL | fn ref_Self<'a>(self: &'a Self, f: &'a u32) -> &u32 {
| ++++ ++ ++

error[E0623]: lifetime mismatch
--> $DIR/lt-ref-self.rs:21:9
Expand All @@ -27,6 +39,12 @@ LL | fn box_ref_Self(self: Box<&Self>, f: &u32) -> &u32 {
| this parameter and the return type are declared with different lifetimes...
LL | f
| ^ ...but data from `f` is returned here
|
= note: each elided lifetime in input position becomes a distinct lifetime
help: consider introducing a named lifetime parameter
|
LL | fn box_ref_Self<'a>(self: Box<&'a Self>, f: &'a u32) -> &u32 {
| ++++ ++ ++

error[E0623]: lifetime mismatch
--> $DIR/lt-ref-self.rs:25:9
Expand All @@ -37,6 +55,12 @@ LL | fn pin_ref_Self(self: Pin<&Self>, f: &u32) -> &u32 {
| this parameter and the return type are declared with different lifetimes...
LL | f
| ^ ...but data from `f` is returned here
|
= note: each elided lifetime in input position becomes a distinct lifetime
help: consider introducing a named lifetime parameter
|
LL | fn pin_ref_Self<'a>(self: Pin<&'a Self>, f: &'a u32) -> &u32 {
| ++++ ++ ++

error[E0623]: lifetime mismatch
--> $DIR/lt-ref-self.rs:29:9
Expand All @@ -47,6 +71,12 @@ LL | fn box_box_ref_Self(self: Box<Box<&Self>>, f: &u32) -> &u32 {
| this parameter and the return type are declared with different lifetimes...
LL | f
| ^ ...but data from `f` is returned here
|
= note: each elided lifetime in input position becomes a distinct lifetime
help: consider introducing a named lifetime parameter
|
LL | fn box_box_ref_Self<'a>(self: Box<Box<&'a Self>>, f: &'a u32) -> &u32 {
| ++++ ++ ++

error[E0623]: lifetime mismatch
--> $DIR/lt-ref-self.rs:33:9
Expand All @@ -57,6 +87,12 @@ LL | fn box_pin_Self(self: Box<Pin<&Self>>, f: &u32) -> &u32 {
| this parameter and the return type are declared with different lifetimes...
LL | f
| ^ ...but data from `f` is returned here
|
= note: each elided lifetime in input position becomes a distinct lifetime
help: consider introducing a named lifetime parameter
|
LL | fn box_pin_Self<'a>(self: Box<Pin<&'a Self>>, f: &'a u32) -> &u32 {
| ++++ ++ ++

error: aborting due to 6 previous errors

Expand Down
36 changes: 36 additions & 0 deletions src/test/ui/self/elision/ref-mut-self.stderr
View file
Expand Up @@ -7,6 +7,12 @@ LL | fn ref_self(&mut self, f: &u32) -> &u32 {
| this parameter and the return type are declared with different lifetimes...
LL | f
| ^ ...but data from `f` is returned here
|
= note: each elided lifetime in input position becomes a distinct lifetime
help: consider introducing a named lifetime parameter
|
LL | fn ref_self<'a>(&'a mut self, f: &'a u32) -> &u32 {
| ++++ ++ ++

error[E0623]: lifetime mismatch
--> $DIR/ref-mut-self.rs:17:9
Expand All @@ -17,6 +23,12 @@ LL | fn ref_Self(self: &mut Self, f: &u32) -> &u32 {
| this parameter and the return type are declared with different lifetimes...
LL | f
| ^ ...but data from `f` is returned here
|
= note: each elided lifetime in input position becomes a distinct lifetime
help: consider introducing a named lifetime parameter
|
LL | fn ref_Self<'a>(self: &'a mut Self, f: &'a u32) -> &u32 {
| ++++ ++ ++

error[E0623]: lifetime mismatch
--> $DIR/ref-mut-self.rs:21:9
Expand All @@ -27,6 +39,12 @@ LL | fn box_ref_Self(self: Box<&mut Self>, f: &u32) -> &u32 {
| this parameter and the return type are declared with different lifetimes...
LL | f
| ^ ...but data from `f` is returned here
|
= note: each elided lifetime in input position becomes a distinct lifetime
help: consider introducing a named lifetime parameter
|
LL | fn box_ref_Self<'a>(self: Box<&'a mut Self>, f: &'a u32) -> &u32 {
| ++++ ++ ++

error[E0623]: lifetime mismatch
--> $DIR/ref-mut-self.rs:25:9
Expand All @@ -37,6 +55,12 @@ LL | fn pin_ref_Self(self: Pin<&mut Self>, f: &u32) -> &u32 {
| this parameter and the return type are declared with different lifetimes...
LL | f
| ^ ...but data from `f` is returned here
|
= note: each elided lifetime in input position becomes a distinct lifetime
help: consider introducing a named lifetime parameter
|
LL | fn pin_ref_Self<'a>(self: Pin<&'a mut Self>, f: &'a u32) -> &u32 {
| ++++ ++ ++

error[E0623]: lifetime mismatch
--> $DIR/ref-mut-self.rs:29:9
Expand All @@ -47,6 +71,12 @@ LL | fn box_box_ref_Self(self: Box<Box<&mut Self>>, f: &u32) -> &u32 {
| this parameter and the return type are declared with different lifetimes...
LL | f
| ^ ...but data from `f` is returned here
|
= note: each elided lifetime in input position becomes a distinct lifetime
help: consider introducing a named lifetime parameter
|
LL | fn box_box_ref_Self<'a>(self: Box<Box<&'a mut Self>>, f: &'a u32) -> &u32 {
| ++++ ++ ++

error[E0623]: lifetime mismatch
--> $DIR/ref-mut-self.rs:33:9
Expand All @@ -57,6 +87,12 @@ LL | fn box_pin_ref_Self(self: Box<Pin<&mut Self>>, f: &u32) -> &u32 {
| this parameter and the return type are declared with different lifetimes...
LL | f
| ^ ...but data from `f` is returned here
|
= note: each elided lifetime in input position becomes a distinct lifetime
help: consider introducing a named lifetime parameter
|
LL | fn box_pin_ref_Self<'a>(self: Box<Pin<&'a mut Self>>, f: &'a u32) -> &u32 {
| ++++ ++ ++

error: aborting due to 6 previous errors

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