Rollup merge of #124682 - estebank:issue-40990, r=pnkfelix
Suggest setting lifetime in borrowck error involving types with elided lifetimes
```
error: lifetime may not live long enough
--> $DIR/ex3-both-anon-regions-both-are-structs-2.rs:7:5
|
LL | fn foo(mut x: Ref, y: Ref) {
| ----- - has type `Ref<'_, '1>`
| |
| has type `Ref<'_, '2>`
LL | x.b = y.b;
| ^^^^^^^^^ assignment requires that `'1` must outlive `'2`
|
help: consider introducing a named lifetime parameter
|
LL | fn foo<'a>(mut x: Ref<'a, 'a>, y: Ref<'a, 'a>) {
| ++++ ++++++++ ++++++++
```
As can be seen above, it currently doesn't try to compare the `ty::Ty` lifetimes that diverged vs the `hir::Ty` to correctly suggest the following
```
help: consider introducing a named lifetime parameter
|
LL | fn foo<'a>(mut x: Ref<'_, 'a>, y: Ref<'_, 'a>) {
| ++++ ++++++++ ++++++++
```
but I believe this to still be an improvement over the status quo.
Fix #40990.
This commit is contained in:
Matthias Krüger
GitHub
commit
29c603c1fa
42 changed files with 697 additions and 215 deletions
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@ -1,9 +1,11 @@
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use hir::GenericParamKind;
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use rustc_data_structures::fx::FxHashSet;
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use rustc_errors::{
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codes::*, Applicability, Diag, DiagMessage, DiagStyledString, EmissionGuarantee, IntoDiagArg,
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MultiSpan, SubdiagMessageOp, Subdiagnostic,
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};
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use rustc_hir as hir;
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use rustc_hir::intravisit::{walk_ty, Visitor};
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use rustc_hir::FnRetTy;
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use rustc_macros::{Diagnostic, Subdiagnostic};
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use rustc_middle::ty::print::TraitRefPrintOnlyTraitPath;
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@ -355,31 +357,33 @@ impl Subdiagnostic for AddLifetimeParamsSuggestion<'_> {
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_f: &F,
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) {
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let mut mk_suggestion = || {
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let (
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hir::Ty { kind: hir::TyKind::Ref(lifetime_sub, _), .. },
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hir::Ty { kind: hir::TyKind::Ref(lifetime_sup, _), .. },
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) = (self.ty_sub, self.ty_sup)
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else {
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return false;
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};
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if !lifetime_sub.is_anonymous() || !lifetime_sup.is_anonymous() {
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return false;
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};
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let Some(anon_reg) = self.tcx.is_suitable_region(self.sub) else {
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return false;
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};
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let node = self.tcx.hir_node_by_def_id(anon_reg.def_id);
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let is_impl = matches!(&node, hir::Node::ImplItem(_));
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let generics = match node {
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let (generics, parent_generics) = match node {
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hir::Node::Item(&hir::Item {
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kind: hir::ItemKind::Fn(_, ref generics, ..),
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..
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})
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| hir::Node::TraitItem(&hir::TraitItem { ref generics, .. })
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| hir::Node::ImplItem(&hir::ImplItem { ref generics, .. }) => generics,
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| hir::Node::ImplItem(&hir::ImplItem { ref generics, .. }) => (
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generics,
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match self.tcx.parent_hir_node(self.tcx.local_def_id_to_hir_id(anon_reg.def_id))
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{
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hir::Node::Item(hir::Item {
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kind: hir::ItemKind::Trait(_, _, ref generics, ..),
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..
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})
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| hir::Node::Item(hir::Item {
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kind: hir::ItemKind::Impl(hir::Impl { ref generics, .. }),
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..
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}) => Some(generics),
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_ => None,
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},
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),
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_ => return false,
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};
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@ -390,24 +394,112 @@ impl Subdiagnostic for AddLifetimeParamsSuggestion<'_> {
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.map(|p| p.name.ident().name)
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.find(|i| *i != kw::UnderscoreLifetime);
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let introduce_new = suggestion_param_name.is_none();
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let mut default = "'a".to_string();
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if let Some(parent_generics) = parent_generics {
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let used: FxHashSet<_> = parent_generics
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.params
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.iter()
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.filter(|p| matches!(p.kind, GenericParamKind::Lifetime { .. }))
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.map(|p| p.name.ident().name)
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.filter(|i| *i != kw::UnderscoreLifetime)
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.map(|l| l.to_string())
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.collect();
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if let Some(lt) =
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('a'..='z').map(|it| format!("'{it}")).find(|it| !used.contains(it))
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{
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// We want a lifetime that *isn't* present in the `trait` or `impl` that assoc
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// `fn` belongs to. We could suggest reusing one of their lifetimes, but it is
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// likely to be an over-constraining lifetime requirement, so we always add a
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// lifetime to the `fn`.
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default = lt;
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}
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}
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let suggestion_param_name =
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suggestion_param_name.map(|n| n.to_string()).unwrap_or_else(|| "'a".to_owned());
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suggestion_param_name.map(|n| n.to_string()).unwrap_or_else(|| default);
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debug!(?lifetime_sup.ident.span);
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debug!(?lifetime_sub.ident.span);
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let make_suggestion = |ident: Ident| {
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let sugg = if ident.name == kw::Empty {
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format!("{suggestion_param_name}, ")
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} else if ident.name == kw::UnderscoreLifetime && ident.span.is_empty() {
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format!("{suggestion_param_name} ")
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} else {
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suggestion_param_name.clone()
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};
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(ident.span, sugg)
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struct ImplicitLifetimeFinder {
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suggestions: Vec<(Span, String)>,
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suggestion_param_name: String,
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}
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impl<'v> Visitor<'v> for ImplicitLifetimeFinder {
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fn visit_ty(&mut self, ty: &'v hir::Ty<'v>) {
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let make_suggestion = |ident: Ident| {
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if ident.name == kw::Empty && ident.span.is_empty() {
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format!("{}, ", self.suggestion_param_name)
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} else if ident.name == kw::UnderscoreLifetime && ident.span.is_empty() {
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format!("{} ", self.suggestion_param_name)
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} else {
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self.suggestion_param_name.clone()
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}
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};
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match ty.kind {
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hir::TyKind::Path(hir::QPath::Resolved(_, path)) => {
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for segment in path.segments {
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if let Some(args) = segment.args {
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if args.args.iter().all(|arg| {
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matches!(
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arg,
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hir::GenericArg::Lifetime(lifetime)
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if lifetime.ident.name == kw::Empty
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)
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}) {
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self.suggestions.push((
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segment.ident.span.shrink_to_hi(),
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format!(
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"<{}>",
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args.args
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.iter()
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.map(|_| self.suggestion_param_name.clone())
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.collect::<Vec<_>>()
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.join(", ")
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),
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));
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} else {
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for arg in args.args {
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if let hir::GenericArg::Lifetime(lifetime) = arg
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&& lifetime.is_anonymous()
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{
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self.suggestions.push((
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lifetime.ident.span,
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make_suggestion(lifetime.ident),
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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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hir::TyKind::Ref(lifetime, ..) if lifetime.is_anonymous() => {
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self.suggestions
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.push((lifetime.ident.span, make_suggestion(lifetime.ident)));
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}
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_ => {}
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}
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walk_ty(self, ty);
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}
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}
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let mut visitor = ImplicitLifetimeFinder {
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suggestions: vec![],
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suggestion_param_name: suggestion_param_name.clone(),
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};
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let mut suggestions =
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vec![make_suggestion(lifetime_sub.ident), make_suggestion(lifetime_sup.ident)];
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if let Some(fn_decl) = node.fn_decl()
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&& let hir::FnRetTy::Return(ty) = fn_decl.output
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{
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visitor.visit_ty(ty);
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}
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if visitor.suggestions.is_empty() {
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// Do not suggest constraining the `&self` param, but rather the return type.
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// If that is wrong (because it is not sufficient), a follow up error will tell the
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// user to fix it. This way we lower the chances of *over* constraining, but still
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// get the cake of "correctly" contrained in two steps.
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visitor.visit_ty(self.ty_sup);
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}
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visitor.visit_ty(self.ty_sub);
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if visitor.suggestions.is_empty() {
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return false;
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}
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if introduce_new {
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let new_param_suggestion = if let Some(first) =
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generics.params.iter().find(|p| !p.name.ident().span.is_empty())
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@ -417,15 +509,16 @@ impl Subdiagnostic for AddLifetimeParamsSuggestion<'_> {
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(generics.span, format!("<{suggestion_param_name}>"))
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};
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suggestions.push(new_param_suggestion);
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visitor.suggestions.push(new_param_suggestion);
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}
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diag.multipart_suggestion(
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diag.multipart_suggestion_verbose(
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fluent::infer_lifetime_param_suggestion,
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suggestions,
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visitor.suggestions,
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Applicability::MaybeIncorrect,
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);
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diag.arg("is_impl", is_impl);
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diag.arg("is_reuse", !introduce_new);
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true
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};
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if mk_suggestion() && self.add_note {
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