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);
     }