diff --git a/compiler/rustc_parse/src/parser/expr.rs b/compiler/rustc_parse/src/parser/expr.rs
index 20430ece05b06..20398d3321db0 100644
--- a/compiler/rustc_parse/src/parser/expr.rs
+++ b/compiler/rustc_parse/src/parser/expr.rs
@@ -513,7 +513,7 @@ impl<'a> Parser<'a> {
             token::Ident(..) if this.is_mistaken_not_ident_negation() => {
                 make_it!(this, attrs, |this, _| this.recover_not_expr(lo))
             }
-            _ => return this.parse_dot_or_call_expr(Some(attrs.into())),
+            _ => return this.parse_dot_or_call_expr(Some(attrs)),
         }
     }
 
diff --git a/compiler/rustc_parse/src/parser/stmt.rs b/compiler/rustc_parse/src/parser/stmt.rs
index e36ebd5e48113..9a236925eff43 100644
--- a/compiler/rustc_parse/src/parser/stmt.rs
+++ b/compiler/rustc_parse/src/parser/stmt.rs
@@ -97,7 +97,7 @@ impl<'a> Parser<'a> {
             self.mk_stmt(lo, StmtKind::Empty)
         } else if self.token != token::CloseDelim(token::Brace) {
             // Remainder are line-expr stmts.
-            let e = self.parse_expr_res(Restrictions::STMT_EXPR, Some(attrs.into()))?;
+            let e = self.parse_expr_res(Restrictions::STMT_EXPR, Some(attrs))?;
             self.mk_stmt(lo.to(e.span), StmtKind::Expr(e))
         } else {
             self.error_outer_attrs(&attrs.take_for_recovery());
@@ -131,7 +131,7 @@ impl<'a> Parser<'a> {
             };
 
             let expr = this.with_res(Restrictions::STMT_EXPR, |this| {
-                let expr = this.parse_dot_or_call_expr_with(expr, lo, attrs.into())?;
+                let expr = this.parse_dot_or_call_expr_with(expr, lo, attrs)?;
                 this.parse_assoc_expr_with(0, LhsExpr::AlreadyParsed(expr))
             })?;
             Ok((
@@ -213,7 +213,7 @@ impl<'a> Parser<'a> {
     }
 
     fn recover_local_after_let(&mut self, lo: Span, attrs: AttrVec) -> PResult<'a, Stmt> {
-        let local = self.parse_local(attrs.into())?;
+        let local = self.parse_local(attrs)?;
         Ok(self.mk_stmt(lo.to(self.prev_token.span), StmtKind::Local(local)))
     }
 
diff --git a/compiler/rustc_typeck/src/astconv/mod.rs b/compiler/rustc_typeck/src/astconv/mod.rs
index 2e1fb44d3b573..a132cda6fefe9 100644
--- a/compiler/rustc_typeck/src/astconv/mod.rs
+++ b/compiler/rustc_typeck/src/astconv/mod.rs
@@ -1473,7 +1473,6 @@ impl<'o, 'tcx> dyn AstConv<'tcx> + 'o {
                     }),
                     assoc_name,
                 )
-                .into_iter()
             },
             || param_name.to_string(),
             assoc_name,
diff --git a/src/bootstrap/install.rs b/src/bootstrap/install.rs
index 22124ec67f5f3..b427420d57795 100644
--- a/src/bootstrap/install.rs
+++ b/src/bootstrap/install.rs
@@ -53,7 +53,7 @@ fn install_sh(
 }
 
 fn default_path(config: &Option<PathBuf>, default: &str) -> PathBuf {
-    PathBuf::from(config.as_ref().cloned().unwrap_or_else(|| PathBuf::from(default)))
+    config.as_ref().cloned().unwrap_or_else(|| PathBuf::from(default))
 }
 
 fn prepare_dir(mut path: PathBuf) -> String {
diff --git a/src/librustdoc/core.rs b/src/librustdoc/core.rs
index d79c47bbe3de6..e20c84ba053f6 100644
--- a/src/librustdoc/core.rs
+++ b/src/librustdoc/core.rs
@@ -161,7 +161,7 @@ impl<'tcx> DocContext<'tcx> {
             }
             Entry::Occupied(e) => e.into_mut(),
         };
-        *def_index = DefIndex::from(*def_index + 1);
+        *def_index = *def_index + 1;
 
         DefId { krate: crate_num, index: *def_index }
     }
diff --git a/src/librustdoc/json/conversions.rs b/src/librustdoc/json/conversions.rs
index e2652ca378a81..b248fcdefbe7f 100644
--- a/src/librustdoc/json/conversions.rs
+++ b/src/librustdoc/json/conversions.rs
@@ -182,7 +182,7 @@ fn from_clean_item_kind(item: clean::ItemKind, tcx: TyCtxt<'_>) -> ItemEnum {
             bounds: g.into_iter().map(Into::into).collect(),
             default: t.map(Into::into),
         },
-        StrippedItem(inner) => from_clean_item_kind(*inner, tcx).into(),
+        StrippedItem(inner) => from_clean_item_kind(*inner, tcx),
         PrimitiveItem(_) | KeywordItem(_) => {
             panic!("{:?} is not supported for JSON output", item)
         }