Auto merge of rust-lang#15169 - lowr:patch/impl-header-anon-lifetime, r=HKalbasi

Use anonymous lifetime where possible

Because anonymous lifetimes are *super* cool.

More seriously, I believe anonymous lifetimes, especially those in impl headers, reduce cognitive load to a certain extent because they usually signify that they are not relevant in the signature of the methods within (or that we can apply the usual lifetime elision rules even if they are relevant).

Author: bors

crates/hir-def/src/body/pretty.rs

@@ -105,7 +105,7 @@ struct Printer<'a> {
     needs_indent: bool,
 }
 
-impl<'a> Write for Printer<'a> {
+impl Write for Printer<'_> {
     fn write_str(&mut self, s: &str) -> fmt::Result {
         for line in s.split_inclusive('\n') {
             if self.needs_indent {
@@ -125,7 +125,7 @@ impl<'a> Write for Printer<'a> {
     }
 }
 
-impl<'a> Printer<'a> {
+impl Printer<'_> {
     fn indented(&mut self, f: impl FnOnce(&mut Self)) {
         self.indent_level += 1;
         wln!(self);

crates/hir-def/src/item_tree/pretty.rs

@@ -52,7 +52,7 @@ struct Printer<'a> {
     needs_indent: bool,
 }
 
-impl<'a> Printer<'a> {
+impl Printer<'_> {
     fn indented(&mut self, f: impl FnOnce(&mut Self)) {
         self.indent_level += 1;
         wln!(self);
@@ -572,7 +572,7 @@ impl<'a> Printer<'a> {
     }
 }
 
-impl<'a> Write for Printer<'a> {
+impl Write for Printer<'_> {
     fn write_str(&mut self, s: &str) -> fmt::Result {
         for line in s.split_inclusive('\n') {
             if self.needs_indent {

crates/hir-expand/src/lib.rs

@@ -850,7 +850,7 @@ impl<L, R> InFile<Either<L, R>> {
     }
 }
 
-impl<'a> InFile<&'a SyntaxNode> {
+impl InFile<&SyntaxNode> {
     pub fn ancestors_with_macros(
         self,
         db: &dyn db::ExpandDatabase,

crates/hir-expand/src/mod_path.rs

@@ -126,7 +126,7 @@ struct Display<'a> {
     path: &'a ModPath,
 }
 
-impl<'a> fmt::Display for Display<'a> {
+impl fmt::Display for Display<'_> {
     fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
         display_fmt_path(self.db, self.path, f, true)
     }
@@ -137,7 +137,7 @@ struct UnescapedDisplay<'a> {
     path: &'a UnescapedModPath<'a>,
 }
 
-impl<'a> fmt::Display for UnescapedDisplay<'a> {
+impl fmt::Display for UnescapedDisplay<'_> {
     fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
         display_fmt_path(self.db, self.path.0, f, false)
     }

crates/hir-expand/src/name.rs

@@ -24,7 +24,7 @@ enum Repr {
     TupleField(usize),
 }
 
-impl<'a> UnescapedName<'a> {
+impl UnescapedName<'_> {
     /// Returns the textual representation of this name as a [`SmolStr`]. Prefer using this over
     /// [`ToString::to_string`] if possible as this conversion is cheaper in the general case.
     pub fn to_smol_str(&self) -> SmolStr {
@@ -40,7 +40,7 @@ impl<'a> UnescapedName<'a> {
         }
     }
 
-    pub fn display(&'a self, db: &dyn crate::db::ExpandDatabase) -> impl fmt::Display + 'a {
+    pub fn display(&self, db: &dyn crate::db::ExpandDatabase) -> impl fmt::Display + '_ {
         _ = db;
         UnescapedDisplay { name: self }
     }
@@ -162,7 +162,7 @@ struct Display<'a> {
     name: &'a Name,
 }
 
-impl<'a> fmt::Display for Display<'a> {
+impl fmt::Display for Display<'_> {
     fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
         match &self.name.0 {
             Repr::Text(text) => fmt::Display::fmt(&text, f),
@@ -175,7 +175,7 @@ struct UnescapedDisplay<'a> {
     name: &'a UnescapedName<'a>,
 }
 
-impl<'a> fmt::Display for UnescapedDisplay<'a> {
+impl fmt::Display for UnescapedDisplay<'_> {
     fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
         match &self.name.0 .0 {
             Repr::Text(text) => {

crates/hir-ty/src/chalk_db.rs

@@ -46,7 +46,7 @@ pub(crate) type AssociatedTyValue = chalk_solve::rust_ir::AssociatedTyValue<Inte
 pub(crate) type FnDefDatum = chalk_solve::rust_ir::FnDefDatum<Interner>;
 pub(crate) type Variances = chalk_ir::Variances<Interner>;
 
-impl<'a> chalk_solve::RustIrDatabase<Interner> for ChalkContext<'a> {
+impl chalk_solve::RustIrDatabase<Interner> for ChalkContext<'_> {
     fn associated_ty_data(&self, id: AssocTypeId) -> Arc<AssociatedTyDatum> {
         self.db.associated_ty_data(id)
     }

crates/hir-ty/src/display.rs

@@ -192,7 +192,7 @@ pub trait HirDisplay {
     }
 }
 
-impl<'a> HirFormatter<'a> {
+impl HirFormatter<'_> {
     pub fn write_joined<T: HirDisplay>(
         &mut self,
         iter: impl IntoIterator<Item = T>,
@@ -342,7 +342,7 @@ impl<T: HirDisplay> HirDisplayWrapper<'_, T> {
     }
 }
 
-impl<'a, T> fmt::Display for HirDisplayWrapper<'a, T>
+impl<T> fmt::Display for HirDisplayWrapper<'_, T>
 where
     T: HirDisplay,
 {
@@ -360,7 +360,7 @@ where
 
 const TYPE_HINT_TRUNCATION: &str = "…";
 
-impl<T: HirDisplay> HirDisplay for &'_ T {
+impl<T: HirDisplay> HirDisplay for &T {
     fn hir_fmt(&self, f: &mut HirFormatter<'_>) -> Result<(), HirDisplayError> {
         HirDisplay::hir_fmt(*self, f)
     }

crates/hir-ty/src/infer/coerce.rs

@@ -220,7 +220,7 @@ pub(crate) fn coerce(
     Ok((adjustments, table.resolve_with_fallback(ty, &fallback)))
 }
 
-impl<'a> InferenceContext<'a> {
+impl InferenceContext<'_> {
     /// Unify two types, but may coerce the first one to the second one
     /// using "implicit coercion rules" if needed.
     pub(super) fn coerce(
@@ -239,7 +239,7 @@ impl<'a> InferenceContext<'a> {
     }
 }
 
-impl<'a> InferenceTable<'a> {
+impl InferenceTable<'_> {
     /// Unify two types, but may coerce the first one to the second one
     /// using "implicit coercion rules" if needed.
     pub(crate) fn coerce(

crates/hir-ty/src/infer/expr.rs

@@ -50,7 +50,7 @@ use super::{
     InferenceContext, InferenceDiagnostic, TypeMismatch,
 };
 
-impl<'a> InferenceContext<'a> {
+impl InferenceContext<'_> {
     pub(crate) fn infer_expr(&mut self, tgt_expr: ExprId, expected: &Expectation) -> Ty {
         let ty = self.infer_expr_inner(tgt_expr, expected);
         if let Some(expected_ty) = expected.only_has_type(&mut self.table) {

crates/hir-ty/src/infer/mutability.rs

@@ -12,7 +12,7 @@ use crate::{lower::lower_to_chalk_mutability, Adjust, Adjustment, AutoBorrow, Ov
 
 use super::InferenceContext;
 
-impl<'a> InferenceContext<'a> {
+impl InferenceContext<'_> {
     pub(crate) fn infer_mut_body(&mut self) {
         self.infer_mut_expr(self.body.body_expr, Mutability::Not);
     }

crates/hir-ty/src/infer/pat.rs

@@ -56,7 +56,7 @@ impl PatLike for PatId {
     }
 }
 
-impl<'a> InferenceContext<'a> {
+impl InferenceContext<'_> {
     /// Infers type for tuple struct pattern or its corresponding assignee expression.
     ///
     /// Ellipses found in the original pattern or expression must be filtered out.

crates/hir-ty/src/infer/unify.rs

@@ -22,7 +22,7 @@ use crate::{
     TraitEnvironment, Ty, TyBuilder, TyExt, TyKind, VariableKind,
 };
 
-impl<'a> InferenceContext<'a> {
+impl InferenceContext<'_> {
     pub(super) fn canonicalize<T: TypeFoldable<Interner> + HasInterner<Interner = Interner>>(
         &mut self,
         t: T,
@@ -547,7 +547,7 @@ impl<'a> InferenceTable<'a> {
             table: &'a mut InferenceTable<'b>,
             highest_known_var: InferenceVar,
         }
-        impl<'a, 'b> TypeFolder<Interner> for VarFudger<'a, 'b> {
+        impl TypeFolder<Interner> for VarFudger<'_, '_> {
             fn as_dyn(&mut self) -> &mut dyn TypeFolder<Interner, Error = Self::Error> {
                 self
             }
@@ -798,7 +798,7 @@ impl<'a> InferenceTable<'a> {
     }
 }
 
-impl<'a> fmt::Debug for InferenceTable<'a> {
+impl fmt::Debug for InferenceTable<'_> {
     fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
         f.debug_struct("InferenceTable").field("num_vars", &self.type_variable_table.len()).finish()
     }
@@ -826,7 +826,7 @@ mod resolve {
         pub(super) var_stack: &'a mut Vec<InferenceVar>,
         pub(super) fallback: F,
     }
-    impl<'a, 'b, F> TypeFolder<Interner> for Resolver<'a, 'b, F>
+    impl<F> TypeFolder<Interner> for Resolver<'_, '_, F>
     where
         F: Fn(InferenceVar, VariableKind, GenericArg, DebruijnIndex) -> GenericArg,
     {

crates/hir-ty/src/lower.rs

@@ -959,10 +959,10 @@ impl<'a> TyLoweringContext<'a> {
     }
 
     pub(crate) fn lower_where_predicate(
-        &'a self,
-        where_predicate: &'a WherePredicate,
+        &self,
+        where_predicate: &WherePredicate,
         ignore_bindings: bool,
-    ) -> impl Iterator<Item = QuantifiedWhereClause> + 'a {
+    ) -> impl Iterator<Item = QuantifiedWhereClause> {
         match where_predicate {
             WherePredicate::ForLifetime { target, bound, .. }
             | WherePredicate::TypeBound { target, bound } => {

crates/hir-ty/src/traits.rs

@@ -170,7 +170,7 @@ fn solve(
 
 struct LoggingRustIrDatabaseLoggingOnDrop<'a>(LoggingRustIrDatabase<Interner, ChalkContext<'a>>);
 
-impl<'a> Drop for LoggingRustIrDatabaseLoggingOnDrop<'a> {
+impl Drop for LoggingRustIrDatabaseLoggingOnDrop<'_> {
     fn drop(&mut self) {
         eprintln!("chalk program:\n{}", self.0);
     }

crates/hir-ty/src/utils.rs

@@ -89,7 +89,7 @@ struct SuperTraits<'a> {
     seen: FxHashSet<ChalkTraitId>,
 }
 
-impl<'a> SuperTraits<'a> {
+impl SuperTraits<'_> {
     fn elaborate(&mut self, trait_ref: &TraitRef) {
         direct_super_trait_refs(self.db, trait_ref, |trait_ref| {
             if !self.seen.contains(&trait_ref.trait_id) {
@@ -99,7 +99,7 @@ impl<'a> SuperTraits<'a> {
     }
 }
 
-impl<'a> Iterator for SuperTraits<'a> {
+impl Iterator for SuperTraits<'_> {
     type Item = TraitRef;
 
     fn next(&mut self) -> Option<Self::Item> {

crates/hir/src/semantics.rs

@@ -1631,7 +1631,7 @@ pub struct SemanticsScope<'a> {
     resolver: Resolver,
 }
 
-impl<'a> SemanticsScope<'a> {
+impl SemanticsScope<'_> {
     pub fn module(&self) -> Module {
         Module { id: self.resolver.module() }
     }

crates/ide-assists/src/handlers/pull_assignment_up.rs

@@ -102,7 +102,7 @@ struct AssignmentsCollector<'a> {
     assignments: Vec<(ast::BinExpr, ast::Expr)>,
 }
 
-impl<'a> AssignmentsCollector<'a> {
+impl AssignmentsCollector<'_> {
     fn collect_match(&mut self, match_expr: &ast::MatchExpr) -> Option<()> {
         for arm in match_expr.match_arm_list()?.arms() {
             match arm.expr()? {

crates/ide-db/src/path_transform.rs

@@ -195,7 +195,7 @@ fn postorder(item: &SyntaxNode) -> impl Iterator<Item = SyntaxNode> {
     })
 }
 
-impl<'a> Ctx<'a> {
+impl Ctx<'_> {
     fn apply(&self, item: &SyntaxNode) {
         // `transform_path` may update a node's parent and that would break the
         // tree traversal. Thus all paths in the tree are collected into a vec

crates/ide-db/src/search.rs

@@ -338,21 +338,21 @@ pub struct FindUsages<'a> {
     search_self_mod: bool,
 }
 
-impl<'a> FindUsages<'a> {
+impl FindUsages<'_> {
     /// Enable searching for `Self` when the definition is a type or `self` for modules.
-    pub fn include_self_refs(mut self) -> FindUsages<'a> {
+    pub fn include_self_refs(mut self) -> Self {
         self.include_self_kw_refs = def_to_ty(self.sema, &self.def);
         self.search_self_mod = true;
         self
     }
 
     /// Limit the search to a given [`SearchScope`].
-    pub fn in_scope(self, scope: SearchScope) -> FindUsages<'a> {
+    pub fn in_scope(self, scope: SearchScope) -> Self {
         self.set_scope(Some(scope))
     }
 
     /// Limit the search to a given [`SearchScope`].
-    pub fn set_scope(mut self, scope: Option<SearchScope>) -> FindUsages<'a> {
+    pub fn set_scope(mut self, scope: Option<SearchScope>) -> Self {
         assert!(self.scope.is_none());
         self.scope = scope;
         self

crates/ide-diagnostics/src/lib.rs

@@ -194,7 +194,7 @@ struct DiagnosticsContext<'a> {
     resolve: &'a AssistResolveStrategy,
 }
 
-impl<'a> DiagnosticsContext<'a> {
+impl DiagnosticsContext<'_> {
     fn resolve_precise_location(
         &self,
         node: &InFile<SyntaxNodePtr>,

crates/ide-ssr/src/search.rs

@@ -22,7 +22,7 @@ pub(crate) struct UsageCache {
     usages: Vec<(Definition, UsageSearchResult)>,
 }
 
-impl<'db> MatchFinder<'db> {
+impl MatchFinder<'_> {
     /// Adds all matches for `rule` to `matches_out`. Matches may overlap in ways that make
     /// replacement impossible, so further processing is required in order to properly nest matches
     /// and remove overlapping matches. This is done in the `nesting` module.

crates/mbe/src/expander/matcher.rs

@@ -884,7 +884,7 @@ impl<'a> Iterator for OpDelimitedIter<'a> {
     }
 }
 
-impl<'a> TtIter<'a> {
+impl TtIter<'_> {
     fn expect_separator(&mut self, separator: &Separator) -> bool {
         let mut fork = self.clone();
         let ok = match separator {

crates/mbe/src/syntax_bridge.rs

@@ -509,25 +509,25 @@ trait TokenConverter: Sized {
     fn id_alloc(&mut self) -> &mut TokenIdAlloc;
 }
 
-impl<'a> SrcToken<RawConverter<'a>> for usize {
-    fn kind(&self, ctx: &RawConverter<'a>) -> SyntaxKind {
+impl SrcToken<RawConverter<'_>> for usize {
+    fn kind(&self, ctx: &RawConverter<'_>) -> SyntaxKind {
         ctx.lexed.kind(*self)
     }
 
-    fn to_char(&self, ctx: &RawConverter<'a>) -> Option<char> {
+    fn to_char(&self, ctx: &RawConverter<'_>) -> Option<char> {
         ctx.lexed.text(*self).chars().next()
     }
 
     fn to_text(&self, ctx: &RawConverter<'_>) -> SmolStr {
         ctx.lexed.text(*self).into()
     }
 
-    fn synthetic_id(&self, _ctx: &RawConverter<'a>) -> Option<SyntheticTokenId> {
+    fn synthetic_id(&self, _ctx: &RawConverter<'_>) -> Option<SyntheticTokenId> {
         None
     }
 }
 
-impl<'a> TokenConverter for RawConverter<'a> {
+impl TokenConverter for RawConverter<'_> {
     type Token = usize;
 
     fn convert_doc_comment(&self, &token: &usize, span: tt::TokenId) -> Option<Vec<tt::TokenTree>> {
@@ -800,7 +800,7 @@ fn delim_to_str(d: tt::DelimiterKind, closing: bool) -> Option<&'static str> {
     Some(&texts[idx..texts.len() - (1 - idx)])
 }
 
-impl<'a> TtTreeSink<'a> {
+impl TtTreeSink<'_> {
     /// Parses a float literal as if it was a one to two name ref nodes with a dot inbetween.
     /// This occurs when a float literal is used as a field access.
     fn float_split(&mut self, has_pseudo_dot: bool) {

crates/mbe/src/tt_iter.rs

@@ -197,4 +197,4 @@ impl<'a> Iterator for TtIter<'a> {
     }
 }
 
-impl<'a> std::iter::ExactSizeIterator for TtIter<'a> {}
+impl std::iter::ExactSizeIterator for TtIter<'_> {}

crates/parser/src/shortcuts.rs

@@ -24,7 +24,7 @@ pub enum StrStep<'a> {
     Error { msg: &'a str, pos: usize },
 }
 
-impl<'a> LexedStr<'a> {
+impl LexedStr<'_> {
     pub fn to_input(&self) -> crate::Input {
         let mut res = crate::Input::default();
         let mut was_joint = false;