From 76efd398ba5a75247f4ba7e4508a246473ba9940 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Matthias=20Kr=C3=BCger?= <matthias.krueger@famsik.de>
Date: Sat, 19 Aug 2023 17:08:09 +0200
Subject: [PATCH 1/2] instead of collecting newly formatted Strings into one
 String, only create a single String and write!() to it
 (clippy::format_collect)

---
 .../src/method/prelude2021.rs                 | 21 ++++++++++---------
 compiler/rustc_middle/src/ty/diagnostics.rs   |  9 ++++----
 2 files changed, 16 insertions(+), 14 deletions(-)

diff --git a/compiler/rustc_hir_typeck/src/method/prelude2021.rs b/compiler/rustc_hir_typeck/src/method/prelude2021.rs
index 5b19a4c525f8d..3f1dca5b1deaa 100644
--- a/compiler/rustc_hir_typeck/src/method/prelude2021.rs
+++ b/compiler/rustc_hir_typeck/src/method/prelude2021.rs
@@ -14,6 +14,7 @@ use rustc_span::symbol::kw::{Empty, Underscore};
 use rustc_span::symbol::{sym, Ident};
 use rustc_span::Span;
 use rustc_trait_selection::infer::InferCtxtExt;
+use std::fmt::Write;
 
 impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
     pub(super) fn lint_dot_call_from_2018(
@@ -143,16 +144,16 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
 
                     let (self_adjusted, precise) = self.adjust_expr(pick, self_expr, sp);
                     if precise {
-                        let args = args
-                            .iter()
-                            .map(|arg| {
-                                let span = arg.span.find_ancestor_inside(sp).unwrap_or_default();
-                                format!(
-                                    ", {}",
-                                    self.sess().source_map().span_to_snippet(span).unwrap()
-                                )
-                            })
-                            .collect::<String>();
+                        let args = args.iter().fold(String::new(), |mut string, arg| {
+                            let span = arg.span.find_ancestor_inside(sp).unwrap_or_default();
+                            write!(
+                                string,
+                                ", {}",
+                                self.sess().source_map().span_to_snippet(span).unwrap()
+                            )
+                            .unwrap();
+                            string
+                        });
 
                         lint.span_suggestion(
                             sp,
diff --git a/compiler/rustc_middle/src/ty/diagnostics.rs b/compiler/rustc_middle/src/ty/diagnostics.rs
index e71482326da79..5db9b775a0f04 100644
--- a/compiler/rustc_middle/src/ty/diagnostics.rs
+++ b/compiler/rustc_middle/src/ty/diagnostics.rs
@@ -1,6 +1,7 @@
 //! Diagnostics related methods for `Ty`.
 
 use std::borrow::Cow;
+use std::fmt::Write;
 use std::ops::ControlFlow;
 
 use crate::ty::{
@@ -335,10 +336,10 @@ pub fn suggest_constraining_type_params<'a>(
             //                                           - insert: `, X: Bar`
             suggestions.push((
                 generics.tail_span_for_predicate_suggestion(),
-                constraints
-                    .iter()
-                    .map(|&(constraint, _)| format!(", {param_name}: {constraint}"))
-                    .collect::<String>(),
+                constraints.iter().fold(String::new(), |mut string, &(constraint, _)| {
+                    write!(string, ", {param_name}: {constraint}").unwrap();
+                    string
+                }),
                 SuggestChangingConstraintsMessage::RestrictTypeFurther { ty: param_name },
             ));
             continue;

From 4cd3b0b71ca1bcabb3b6ff7be6410d96356d9768 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Matthias=20Kr=C3=BCger?= <matthias.krueger@famsik.de>
Date: Sat, 19 Aug 2023 18:49:58 +0200
Subject: [PATCH 2/2] use static arrays instead of vectors

---
 compiler/rustc_mir_transform/src/coverage/debug.rs | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/compiler/rustc_mir_transform/src/coverage/debug.rs b/compiler/rustc_mir_transform/src/coverage/debug.rs
index d2c0c4ba06922..083f1f8aef692 100644
--- a/compiler/rustc_mir_transform/src/coverage/debug.rs
+++ b/compiler/rustc_mir_transform/src/coverage/debug.rs
@@ -199,9 +199,9 @@ impl DebugOptions {
 
 fn bool_option_val(option: &str, some_strval: Option<&str>) -> bool {
     if let Some(val) = some_strval {
-        if vec!["yes", "y", "on", "true"].contains(&val) {
+        if ["yes", "y", "on", "true"].contains(&val) {
             true
-        } else if vec!["no", "n", "off", "false"].contains(&val) {
+        } else if ["no", "n", "off", "false"].contains(&val) {
             false
         } else {
             bug!(