mirror of https://github.com/rust-lang/rust.git
Add beginner friendly lifetime elision hint to E0623
Suggest adding a new lifetime parameter when two elided lifetimes should match up but don't Issue #90170 This also changes the tests introduced by the previous commits because of another rustc issue (#90258)
This commit is contained in:
Nilstrieb
parent
18bc4bee97
commit
4b9e4606cb
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@ -7,7 +7,10 @@ use crate::infer::error_reporting::nice_region_error::NiceRegionError;
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use crate::infer::lexical_region_resolve::RegionResolutionError;
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use crate::infer::SubregionOrigin;
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use rustc_errors::{struct_span_err, ErrorReported};
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use rustc_errors::{struct_span_err, Applicability, DiagnosticBuilder, ErrorReported};
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use rustc_hir as hir;
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use rustc_hir::{GenericParamKind, Ty};
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use rustc_middle::ty::Region;
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impl<'a, 'tcx> NiceRegionError<'a, 'tcx> {
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/// Print the error message for lifetime errors when both the concerned regions are anonymous.
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@ -160,11 +163,13 @@ impl<'a, 'tcx> NiceRegionError<'a, 'tcx> {
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}
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};
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let mut e = struct_span_err!(self.tcx().sess, span, E0623, "lifetime mismatch");
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let mut err = struct_span_err!(self.tcx().sess, span, E0623, "lifetime mismatch");
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e.span_label(span_1, main_label);
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e.span_label(span_2, String::new());
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e.span_label(span, span_label);
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err.span_label(span_1, main_label);
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err.span_label(span_2, String::new());
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err.span_label(span, span_label);
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self.suggest_adding_lifetime_params(sub, ty_sup, ty_sub, &mut err);
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if let Some(t) = future_return_type {
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let snip = self
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@ -178,14 +183,87 @@ impl<'a, 'tcx> NiceRegionError<'a, 'tcx> {
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(_, "") => None,
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_ => Some(s),
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})
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.unwrap_or("{unnamed_type}".to_string());
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.unwrap_or_else(|| "{unnamed_type}".to_string());
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e.span_label(
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err.span_label(
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t.span,
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&format!("this `async fn` implicitly returns an `impl Future<Output = {}>`", snip),
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);
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}
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e.emit();
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err.emit();
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Some(ErrorReported)
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}
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fn suggest_adding_lifetime_params(
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&self,
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sub: Region<'tcx>,
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ty_sup: &Ty<'_>,
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ty_sub: &Ty<'_>,
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err: &mut DiagnosticBuilder<'_>,
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) {
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if let (
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hir::Ty { kind: hir::TyKind::Rptr(lifetime_sub, _), .. },
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hir::Ty { kind: hir::TyKind::Rptr(lifetime_sup, _), .. },
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) = (ty_sub, ty_sup)
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{
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if lifetime_sub.name.is_elided() && lifetime_sup.name.is_elided() {
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if let Some(anon_reg) = self.tcx().is_suitable_region(sub) {
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let hir_id = self.tcx().hir().local_def_id_to_hir_id(anon_reg.def_id);
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if let hir::Node::Item(&hir::Item {
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kind: hir::ItemKind::Fn(_, ref generics, ..),
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..
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}) = self.tcx().hir().get(hir_id)
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{
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let (suggestion_param_name, introduce_new) = generics
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.params
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.iter()
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.find(|p| matches!(p.kind, GenericParamKind::Lifetime { .. }))
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.and_then(|p| self.tcx().sess.source_map().span_to_snippet(p.span).ok())
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.map(|name| (name, false))
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.unwrap_or_else(|| ("'a".to_string(), true));
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let mut suggestions = vec![
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if let hir::LifetimeName::Underscore = lifetime_sub.name {
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(lifetime_sub.span, suggestion_param_name.clone())
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} else {
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(
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lifetime_sub.span.shrink_to_hi(),
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suggestion_param_name.clone() + " ",
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)
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},
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if let hir::LifetimeName::Underscore = lifetime_sup.name {
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(lifetime_sup.span, suggestion_param_name.clone())
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} else {
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(
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lifetime_sup.span.shrink_to_hi(),
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suggestion_param_name.clone() + " ",
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)
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},
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];
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if introduce_new {
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let new_param_suggestion = match &generics.params {
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[] => (generics.span, format!("<{}>", suggestion_param_name)),
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[first, ..] => (
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first.span.shrink_to_lo(),
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format!("{}, ", suggestion_param_name),
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),
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};
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suggestions.push(new_param_suggestion);
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}
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err.multipart_suggestion(
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"consider introducing a named lifetime parameter",
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suggestions,
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Applicability::MaybeIncorrect,
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);
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err.note(
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"each elided lifetime in input position becomes a distinct lifetime",
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);
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}
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}
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}
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}
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}
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}
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@ -0,0 +1,9 @@
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// run-rustfix
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pub fn foo<'a>(x: &mut Vec<&'a u8>, y: &'a u8) { x.push(y); } //~ ERROR lifetime mismatch
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pub fn foo2<'a>(x: &mut Vec<&'a u8>, y: &'a u8) { x.push(y); } //~ ERROR lifetime mismatch
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pub fn foo3<'a>(_other: &'a [u8], x: &mut Vec<&'a u8>, y: &'a u8) { x.push(y); } //~ ERROR lifetime mismatch
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fn main() {}
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@ -0,0 +1,29 @@
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error: lifetime may not live long enough
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--> $DIR/issue-90170-elision-mismatch.rs:3:40
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LL | pub fn foo(x: &mut Vec<&u8>, y: &u8) { x.push(y); }
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| - - ^^^^^^^^^ argument requires that `'1` must outlive `'2`
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| | |
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| | let's call the lifetime of this reference `'1`
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| let's call the lifetime of this reference `'2`
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error: lifetime may not live long enough
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--> $DIR/issue-90170-elision-mismatch.rs:5:44
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LL | pub fn foo2(x: &mut Vec<&'_ u8>, y: &u8) { x.push(y); }
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| - - ^^^^^^^^^ argument requires that `'1` must outlive `'2`
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| | |
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| | let's call the lifetime of this reference `'1`
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| let's call the lifetime of this reference `'2`
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error: lifetime may not live long enough
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--> $DIR/issue-90170-elision-mismatch.rs:7:63
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LL | pub fn foo3<'a>(_other: &'a [u8], x: &mut Vec<&u8>, y: &u8) { x.push(y); }
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| - - ^^^^^^^^^ argument requires that `'1` must outlive `'2`
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| | |
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| | let's call the lifetime of this reference `'1`
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| let's call the lifetime of this reference `'2`
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error: aborting due to 3 previous errors
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@ -0,0 +1,9 @@
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// run-rustfix
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pub fn foo(x: &mut Vec<&u8>, y: &u8) { x.push(y); } //~ ERROR lifetime mismatch
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pub fn foo2(x: &mut Vec<&'_ u8>, y: &u8) { x.push(y); } //~ ERROR lifetime mismatch
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pub fn foo3<'a>(_other: &'a [u8], x: &mut Vec<&u8>, y: &u8) { x.push(y); } //~ ERROR lifetime mismatch
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fn main() {}
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@ -0,0 +1,45 @@
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error[E0623]: lifetime mismatch
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--> $DIR/issue-90170-elision-mismatch.rs:3:47
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LL | pub fn foo(x: &mut Vec<&u8>, y: &u8) { x.push(y); }
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| --- --- ^ ...but data from `y` flows into `x` here
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| |
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| these two types are declared with different lifetimes...
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= note: each elided lifetime in input position becomes a distinct lifetime
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help: consider introducing a named lifetime parameter
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LL | pub fn foo<'a>(x: &mut Vec<&'a u8>, y: &'a u8) { x.push(y); }
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| ++++ ++ ++
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error[E0623]: lifetime mismatch
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--> $DIR/issue-90170-elision-mismatch.rs:5:51
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LL | pub fn foo2(x: &mut Vec<&'_ u8>, y: &u8) { x.push(y); }
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| ------ --- ^ ...but data from `y` flows into `x` here
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| |
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| these two types are declared with different lifetimes...
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= note: each elided lifetime in input position becomes a distinct lifetime
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help: consider introducing a named lifetime parameter
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LL | pub fn foo2<'a>(x: &mut Vec<&'a u8>, y: &'a u8) { x.push(y); }
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| ++++ ~~ ++
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error[E0623]: lifetime mismatch
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--> $DIR/issue-90170-elision-mismatch.rs:7:70
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LL | pub fn foo3<'a>(_other: &'a [u8], x: &mut Vec<&u8>, y: &u8) { x.push(y); }
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| --- --- ^ ...but data from `y` flows into `x` here
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| |
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| these two types are declared with different lifetimes...
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= note: each elided lifetime in input position becomes a distinct lifetime
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help: consider introducing a named lifetime parameter
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LL | pub fn foo3<'a>(_other: &'a [u8], x: &mut Vec<&'a u8>, y: &'a u8) { x.push(y); }
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| ++ ++
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error: aborting due to 3 previous errors
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For more information about this error, try `rustc --explain E0623`.
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@ -5,6 +5,12 @@ LL | fn foo(&mut (ref mut v, w): &mut (&u8, &u8), x: &u8) {
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| --- --- these two types are declared with different lifetimes...
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LL | *v = x;
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| ^ ...but data from `x` flows here
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= note: each elided lifetime in input position becomes a distinct lifetime
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help: consider introducing a named lifetime parameter
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LL | fn foo<'a>(&mut (ref mut v, w): &mut (&'a u8, &u8), x: &'a u8) {
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| ++++ ++ ++
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error: aborting due to previous error
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@ -5,6 +5,12 @@ LL | fn foo(z: &mut Vec<(&u8,&u8)>, (x, y): (&u8, &u8)) {
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| --- --- these two types are declared with different lifetimes...
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LL | z.push((x,y));
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| ^ ...but data flows into `z` here
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= note: each elided lifetime in input position becomes a distinct lifetime
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help: consider introducing a named lifetime parameter
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LL | fn foo<'a>(z: &mut Vec<(&'a u8,&u8)>, (x, y): (&'a u8, &u8)) {
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| ++++ ++ ++
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error[E0623]: lifetime mismatch
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--> $DIR/ex3-both-anon-regions-3.rs:2:15
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@ -13,6 +19,12 @@ LL | fn foo(z: &mut Vec<(&u8,&u8)>, (x, y): (&u8, &u8)) {
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| --- --- these two types are declared with different lifetimes...
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LL | z.push((x,y));
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| ^ ...but data flows into `z` here
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= note: each elided lifetime in input position becomes a distinct lifetime
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help: consider introducing a named lifetime parameter
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LL | fn foo<'a>(z: &mut Vec<(&u8,&'a u8)>, (x, y): (&u8, &'a u8)) {
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| ++++ ++ ++
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error: aborting due to 2 previous errors
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@ -5,6 +5,12 @@ LL | fn foo(x:fn(&u8, &u8), y: Vec<&u8>, z: &u8) {
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| --- --- these two types are declared with different lifetimes...
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LL | y.push(z);
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| ^ ...but data from `z` flows into `y` here
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= note: each elided lifetime in input position becomes a distinct lifetime
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help: consider introducing a named lifetime parameter
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LL | fn foo<'a>(x:fn(&u8, &u8), y: Vec<&'a u8>, z: &'a u8) {
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| ++++ ++ ++
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error: aborting due to previous error
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@ -5,6 +5,12 @@ LL | fn foo(x:Box<dyn Fn(&u8, &u8)> , y: Vec<&u8>, z: &u8) {
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| --- --- these two types are declared with different lifetimes...
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LL | y.push(z);
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| ^ ...but data from `z` flows into `y` here
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= note: each elided lifetime in input position becomes a distinct lifetime
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help: consider introducing a named lifetime parameter
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LL | fn foo<'a>(x:Box<dyn Fn(&'a u8, &'a u8)> , y: Vec<&u8>, z: &u8) {
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| ++++ ++ ++
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error: aborting due to previous error
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@ -5,6 +5,12 @@ LL | fn foo(x: &mut Vec<&u8>, y: &u8) {
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| --- --- these two types are declared with different lifetimes...
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LL | x.push(y);
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| ^ ...but data from `y` flows into `x` here
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= note: each elided lifetime in input position becomes a distinct lifetime
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help: consider introducing a named lifetime parameter
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LL | fn foo<'a>(x: &mut Vec<&'a u8>, y: &'a u8) {
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| ++++ ++ ++
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error: aborting due to previous error
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@ -5,6 +5,12 @@ LL | fn foo(x: &mut Vec<&'_ u8>, y: &'_ u8) { x.push(y); }
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| ------ ------ ^ ...but data from `y` flows into `x` here
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| |
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| these two types are declared with different lifetimes...
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= note: each elided lifetime in input position becomes a distinct lifetime
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help: consider introducing a named lifetime parameter
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LL | fn foo<'a>(x: &mut Vec<&'a u8>, y: &'a u8) { x.push(y); }
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| ++++ ~~ ~~
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error: aborting due to previous error
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