Auto merge of #13286 - smoelius:elidable-impl-lifetimes, r=Alexendoo

Extend `needless_lifetimes` to suggest eliding `impl` lifetimes
Example:
```
error: the following explicit lifetimes could be elided: 'a
--> tests/ui/needless_lifetimes.rs:332:10
|
LL | impl<'a> Foo for Baz<'a> {}
| ^^ ^^
|
help: elide the lifetimes
|
LL - impl<'a> Foo for Baz<'a> {}
LL + impl Foo for Baz<'_> {}
```
The main change is in how `impl` lifetime uses are tracked. Previously, a hashmap was created, and lifetimes were removed from the hashmap as their uses were discovered. However, the uses are needed to generate elision suggestions. So, now, uses are added to the hashmap as they are discovered.
The PR is currently organized as six commits, which I think are self-explanatory:
- Extend `needless_lifetimes` to suggest eliding `impl` lifetimes
- Reorder functions _[not strictly necessary, but IMHO, the code is better structured as a result]_
- Fix lifetime tests
- Fix non-lifetime tests
- Fix `clippy_lints` and `clippy_utils`
- Fix typo in `needless_lifetimes` test
r? `@Alexendoo` (I think you are `needless_lifetimes`' primary author? Sorry if I have this wrong.)
---
changelog: Extend `needless_lifetimes` to suggest eliding `impl` lifetimes

Author: bors

clippy_lints/src/booleans.rs

@@ -205,7 +205,7 @@ struct Hir2Qmm<'a, 'tcx, 'v> {
 cx:&'aLateContext<'tcx>,
 }
 
-impl<'a,'tcx,'v>Hir2Qmm<'a,'tcx,'v>{
+impl<'v>Hir2Qmm<'_,'_,'v>{
 fnextract(&mutself,op:BinOpKind,a:&[&'vExpr<'_>],mutv:Vec<Bool>) -> Result<Vec<Bool>,String>{
 for a in a {
 ifletExprKind::Binary(binop, lhs, rhs) = &a.kind{
@@ -292,7 +292,7 @@ struct SuggestContext<'a, 'tcx, 'v> {
 output:String,
 }
 
-impl<'a,'tcx,'v>SuggestContext<'a,'tcx,'v>{
+implSuggestContext<'_,'_,'_>{
 fnrecurse(&mutself,suggestion:&Bool) -> Option<()>{
 use quine_mc_cluskey::Bool::{And,False,Not,Or,Term,True};
 match suggestion {
@@ -475,7 +475,7 @@ fn terminal_stats(b: &Bool) -> Stats {
  stats
 }
 
-impl<'a,'tcx>NonminimalBoolVisitor<'a,'tcx>{
+impl<'tcx>NonminimalBoolVisitor<'_,'tcx>{
 fnbool_expr(&self,e:&'tcxExpr<'_>){
 letmut h2q = Hir2Qmm{
 terminals:Vec::new(),
@@ -582,7 +582,7 @@ impl<'a, 'tcx> NonminimalBoolVisitor<'a, 'tcx> {
 }
 }
 
-impl<'a,'tcx>Visitor<'tcx>forNonminimalBoolVisitor<'a,'tcx>{
+impl<'tcx>Visitor<'tcx>forNonminimalBoolVisitor<'_,'tcx>{
 fnvisit_expr(&mutself,e:&'tcxExpr<'_>){
 if !e.span.from_expansion(){
 match&e.kind{

clippy_lints/src/box_default.rs

@@ -91,7 +91,7 @@ fn is_local_vec_expn(cx: &LateContext<'_>, expr: &Expr<'_>, ref_expr: &Expr<'_>)
 #[derive(Default)]
 structInferVisitor(bool);
 
-impl<'tcx>Visitor<'tcx>forInferVisitor{
+implVisitor<'_>forInferVisitor{
 fnvisit_ty(&mutself,t:&Ty<'_>){
 self.0 |= matches!(t.kind,TyKind::Infer | TyKind::OpaqueDef(..) | TyKind::TraitObject(..));
 if !self.0{

clippy_lints/src/checked_conversions.rs

@@ -48,7 +48,7 @@ impl CheckedConversions {
 
 impl_lint_pass!(CheckedConversions => [CHECKED_CONVERSIONS]);
 
-impl<'tcx>LateLintPass<'tcx>forCheckedConversions{
+implLateLintPass<'_>forCheckedConversions{
 fncheck_expr(&mutself,cx:&LateContext<'_>,item:&Expr<'_>){
 ifletExprKind::Binary(op, lhs, rhs) = item.kind
  && let(lt1, gt1, op2) = match op.node{

clippy_lints/src/default_numeric_fallback.rs

@@ -119,7 +119,7 @@ impl<'a, 'tcx> NumericFallbackVisitor<'a, 'tcx> {
 }
 }
 
-impl<'a,'tcx>Visitor<'tcx>forNumericFallbackVisitor<'a,'tcx>{
+impl<'tcx>Visitor<'tcx>forNumericFallbackVisitor<'_,'tcx>{
 fnvisit_expr(&mutself,expr:&'tcxExpr<'_>){
 match&expr.kind{
 ExprKind::Block(

clippy_lints/src/doc/mod.rs

@@ -970,7 +970,7 @@ impl<'a, 'tcx> FindPanicUnwrap<'a, 'tcx> {
 }
 }
 
-impl<'a,'tcx>Visitor<'tcx>forFindPanicUnwrap<'a,'tcx>{
+impl<'tcx>Visitor<'tcx>forFindPanicUnwrap<'_,'tcx>{
 typeNestedFilter = nested_filter::OnlyBodies;
 
 fnvisit_expr(&mutself,expr:&'tcxExpr<'_>){

clippy_lints/src/empty_enum.rs

@@ -60,7 +60,7 @@ declare_clippy_lint! {
 
 declare_lint_pass!(EmptyEnum => [EMPTY_ENUM]);
 
-impl<'tcx>LateLintPass<'tcx>forEmptyEnum{
+implLateLintPass<'_>forEmptyEnum{
 fncheck_item(&mutself,cx:&LateContext<'_>,item:&Item<'_>){
 ifletItemKind::Enum(..) = item.kind
 // Only suggest the `never_type` if the feature is enabled

clippy_lints/src/escape.rs

@@ -141,7 +141,7 @@ fn is_argument(tcx: TyCtxt<'_>, id: HirId) -> bool {
 matches!(tcx.parent_hir_node(id),Node::Param(_))
 }
 
-impl<'a,'tcx>Delegate<'tcx>forEscapeDelegate<'a,'tcx>{
+impl<'tcx>Delegate<'tcx>forEscapeDelegate<'_,'tcx>{
 fnconsume(&mutself,cmt:&PlaceWithHirId<'tcx>, _:HirId){
 if cmt.place.projections.is_empty(){
 ifletPlaceBase::Local(lid) = cmt.place.base{
@@ -188,7 +188,7 @@ impl<'a, 'tcx> Delegate<'tcx> for EscapeDelegate<'a, 'tcx> {
 fnfake_read(&mutself, _:&PlaceWithHirId<'tcx>, _:FakeReadCause, _:HirId){}
 }
 
-impl<'a,'tcx>EscapeDelegate<'a,'tcx>{
+impl<'tcx>EscapeDelegate<'_,'tcx>{
 fnis_large_box(&self,ty:Ty<'tcx>) -> bool{
 // Large types need to be boxed to avoid stack overflows.
 ifletSome(boxed_ty) = ty.boxed_ty(){

clippy_lints/src/excessive_nesting.rs

@@ -135,7 +135,7 @@ impl NestingVisitor<'_, '_> {
 }
 }
 
-impl<'conf,'cx>Visitor<'_>forNestingVisitor<'conf,'cx>{
+implVisitor<'_>forNestingVisitor<'_,'_>{
 fnvisit_block(&mutself,block:&Block){
 if block.span.from_expansion(){
 return;

clippy_lints/src/extra_unused_type_parameters.rs

@@ -193,7 +193,7 @@ fn bound_to_trait_def_id(bound: &GenericBound<'_>) -> Option<LocalDefId> {
  bound.trait_ref()?.trait_def_id()?.as_local()
 }
 
-impl<'cx,'tcx>Visitor<'tcx>forTypeWalker<'cx,'tcx>{
+impl<'tcx>Visitor<'tcx>forTypeWalker<'_,'tcx>{
 typeNestedFilter = nested_filter::OnlyBodies;
 
 fnvisit_ty(&mutself,t:&'tcxTy<'tcx>){

clippy_lints/src/fallible_impl_from.rs

@@ -73,7 +73,7 @@ fn lint_impl_body(cx: &LateContext<'_>, impl_span: Span, impl_items: &[hir::Impl
 result:Vec<Span>,
 }
 
-impl<'a,'tcx>Visitor<'tcx>forFindPanicUnwrap<'a,'tcx>{
+impl<'tcx>Visitor<'tcx>forFindPanicUnwrap<'_,'tcx>{
 fnvisit_expr(&mutself,expr:&'tcxExpr<'_>){
 ifletSome(macro_call) = root_macro_call_first_node(self.lcx, expr){
 ifis_panic(self.lcx, macro_call.def_id){