more clippy::perf fixes

compiler/rustc_lint/src/context.rs

@@ -842,7 +842,7 @@ pub trait LintContext: Sized {
                     if let Some(positional_arg_to_replace) = position_sp_to_replace {
                         let name = if is_formatting_arg { named_arg_name + "$" } else { named_arg_name };
                         let span_to_replace = if let Ok(positional_arg_content) =
-                            self.sess().source_map().span_to_snippet(positional_arg_to_replace) && positional_arg_content.starts_with(":") {
+                            self.sess().source_map().span_to_snippet(positional_arg_to_replace) && positional_arg_content.starts_with(':') {
                             positional_arg_to_replace.shrink_to_lo()
                         } else {
                             positional_arg_to_replace

compiler/rustc_metadata/src/rmeta/encoder.rs

@@ -1378,19 +1378,11 @@ impl<'a, 'tcx> EncodeContext<'a, 'tcx> {
 
         let tcx = self.tcx;
 
-        let keys_and_jobs = tcx
-            .mir_keys(())
-            .iter()
-            .filter_map(|&def_id| {
-                let (encode_const, encode_opt) = should_encode_mir(tcx, def_id);
-                if encode_const || encode_opt {
-                    Some((def_id, encode_const, encode_opt))
-                } else {
-                    None
-                }
-            })
-            .collect::<Vec<_>>();
-        for (def_id, encode_const, encode_opt) in keys_and_jobs.into_iter() {
+        let keys_and_jobs = tcx.mir_keys(()).iter().filter_map(|&def_id| {
+            let (encode_const, encode_opt) = should_encode_mir(tcx, def_id);
+            if encode_const || encode_opt { Some((def_id, encode_const, encode_opt)) } else { None }
+        });
+        for (def_id, encode_const, encode_opt) in keys_and_jobs {
             debug_assert!(encode_const || encode_opt);
 
             debug!("EntryBuilder::encode_mir({:?})", def_id);

compiler/rustc_resolve/src/diagnostics.rs

@@ -1393,7 +1393,7 @@ impl<'a> Resolver<'a> {
 
         // If only some candidates are accessible, take just them
         if !candidates.iter().all(|v: &ImportSuggestion| !v.accessible) {
-            candidates = candidates.into_iter().filter(|x| x.accessible).collect();
+            candidates.retain(|x| x.accessible)
         }
 
         candidates

library/std/src/sys/unix/thread.rs

@@ -429,7 +429,7 @@ mod cgroups {
                         Some(b"") => Cgroup::V2,
                         Some(controllers)
                             if from_utf8(controllers)
-                                .is_ok_and(|c| c.split(",").any(|c| c == "cpu")) =>
+                                .is_ok_and(|c| c.split(',').any(|c| c == "cpu")) =>
                         {
                             Cgroup::V1
                         }

src/librustdoc/html/render/mod.rs

@@ -2367,9 +2367,9 @@ pub(crate) fn get_filtered_impls_for_reference<'a>(
     let Some(v) = shared.cache.impls.get(&def_id) else { return (Vec::new(), Vec::new(), Vec::new()) };
     // Since there is no "direct implementation" on the reference primitive type, we filter out
     // every implementation which isn't a trait implementation.
-    let traits: Vec<_> = v.iter().filter(|i| i.inner_impl().trait_.is_some()).collect();
+    let traits = v.iter().filter(|i| i.inner_impl().trait_.is_some());
     let (synthetic, concrete): (Vec<&Impl>, Vec<&Impl>) =
-        traits.into_iter().partition(|t| t.inner_impl().kind.is_auto());
+        traits.partition(|t| t.inner_impl().kind.is_auto());
 
     let (blanket_impl, concrete): (Vec<&Impl>, _) =
         concrete.into_iter().partition(|t| t.inner_impl().kind.is_blanket());

src/librustdoc/html/render/write_shared.rs

@@ -312,7 +312,7 @@ pub(super) fn write_shared(
                 if line.starts_with(&prefix) {
                     continue;
                 }
-                if line.ends_with(",") {
+                if line.ends_with(',') {
                     ret.push(line[..line.len() - 1].to_string());
                 } else {
                     // No comma (it's the case for the last added crate line)