clippy::perf fixes

compiler/rustc_codegen_llvm/src/back/archive.rs

@@ -219,7 +219,7 @@ impl<'a> ArchiveBuilder<'a> for LlvmArchiveBuilder<'a> {
 
             match result {
                 Err(e) => {
-                    self.config.sess.fatal(&format!("Error calling dlltool: {}", e.to_string()));
+                    self.config.sess.fatal(&format!("Error calling dlltool: {}", e));
                 }
                 Ok(output) if !output.status.success() => self.config.sess.fatal(&format!(
                     "Dlltool could not create import library: {}\n{}",

compiler/rustc_interface/src/interface.rs

@@ -126,7 +126,7 @@ pub fn parse_cfgspecs(cfgspecs: Vec<String>) -> FxHashSet<(String, Option<String
 
                 // If the user tried to use a key="value" flag, but is missing the quotes, provide
                 // a hint about how to resolve this.
-                if s.contains("=") && !s.contains("=\"") && !s.ends_with("\"") {
+                if s.contains('=') && !s.contains("=\"") && !s.ends_with('"') {
                     error!(concat!(
                         r#"expected `key` or `key="value"`, ensure escaping is appropriate"#,
                         r#" for your shell, try 'key="value"' or key=\"value\""#

compiler/rustc_parse/src/parser/expr.rs

@@ -1702,11 +1702,11 @@ impl<'a> Parser<'a> {
 
         // Try to lowercase the prefix if it's a valid base prefix.
         fn fix_base_capitalisation(s: &str) -> Option<String> {
-            if let Some(stripped) = s.strip_prefix("B") {
+            if let Some(stripped) = s.strip_prefix('B') {
                 Some(format!("0b{stripped}"))
-            } else if let Some(stripped) = s.strip_prefix("O") {
+            } else if let Some(stripped) = s.strip_prefix('O') {
                 Some(format!("0o{stripped}"))
-            } else if let Some(stripped) = s.strip_prefix("X") {
+            } else if let Some(stripped) = s.strip_prefix('X') {
                 Some(format!("0x{stripped}"))
             } else {
                 None

compiler/rustc_typeck/src/check/expr.rs

@@ -1587,10 +1587,10 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
     ) {
         let len = remaining_fields.len();
 
-        let mut displayable_field_names =
-            remaining_fields.keys().map(|ident| ident.as_str()).collect::<Vec<_>>();
-
-        displayable_field_names.sort();
+        let mut displayable_field_names: Vec<&str> =
+            remaining_fields.keys().map(|ident| ident.as_str()).collect();
+        // sorting &str primitives here, sort_unstable is ok
+        displayable_field_names.sort_unstable();
 
         let mut truncated_fields_error = String::new();
         let remaining_fields_names = match &displayable_field_names[..] {