a couple clippy::complexity fixes

map_identity
filter_next
option_as_ref_deref
unnecessary_find_map
redundant_slicing
unnecessary_unwrap
bool_comparison
derivable_impls
manual_flatten
needless_borrowed_reference

compiler/rustc_codegen_llvm/src/builder.rs

@@ -1190,8 +1190,8 @@ impl<'a, 'll, 'tcx> BuilderMethods<'a, 'tcx> for Builder<'a, 'll, 'tcx> {
         // Set KCFI operand bundle
         let is_indirect_call = unsafe { llvm::LLVMIsAFunction(llfn).is_none() };
         let kcfi_bundle =
-            if self.tcx.sess.is_sanitizer_kcfi_enabled() && fn_abi.is_some() && is_indirect_call {
-                let kcfi_typeid = kcfi_typeid_for_fnabi(self.tcx, fn_abi.unwrap());
+            if let Some(fn_abi) = fn_abi && self.tcx.sess.is_sanitizer_kcfi_enabled() && is_indirect_call {
+                let kcfi_typeid = kcfi_typeid_for_fnabi(self.tcx, fn_abi);
                 Some(llvm::OperandBundleDef::new("kcfi", &[self.const_u32(kcfi_typeid)]))
             } else {
                 None

compiler/rustc_errors/src/emitter.rs

@@ -2235,7 +2235,7 @@ impl EmitterWriter {
             }
         } else if is_multiline {
             buffer.puts(*row_num, 0, &self.maybe_anonymized(line_num), Style::LineNumber);
-            match &highlight_parts[..] {
+            match &highlight_parts {
                 [SubstitutionHighlight { start: 0, end }] if *end == line_to_add.len() => {
                     buffer.puts(*row_num, max_line_num_len + 1, "+ ", Style::Addition);
                 }

compiler/rustc_infer/src/infer/error_reporting/mod.rs

@@ -2399,10 +2399,8 @@ impl<'tcx> TypeErrCtxt<'_, 'tcx> {
                 let suggestion =
                     if has_lifetimes { format!(" + {}", sub) } else { format!(": {}", sub) };
                 let mut suggestions = vec![(sp, suggestion)];
-                for add_lt_sugg in add_lt_suggs {
-                    if let Some(add_lt_sugg) = add_lt_sugg {
-                        suggestions.push(add_lt_sugg);
-                    }
+                for add_lt_sugg in add_lt_suggs.into_iter().flatten() {
+                    suggestions.push(add_lt_sugg);
                 }
                 err.multipart_suggestion_verbose(
                     format!("{msg}..."),
@@ -2426,11 +2424,9 @@ impl<'tcx> TypeErrCtxt<'_, 'tcx> {
                     };
                     let mut sugg =
                         vec![(sp, suggestion), (span.shrink_to_hi(), format!(" + {}", new_lt))];
-                    for add_lt_sugg in add_lt_suggs.clone() {
-                        if let Some(lt) = add_lt_sugg {
-                            sugg.push(lt);
-                            sugg.rotate_right(1);
-                        }
+                    for lt in add_lt_suggs.clone().into_iter().flatten() {
+                        sugg.push(lt);
+                        sugg.rotate_right(1);
                     }
                     // `MaybeIncorrect` due to issue #41966.
                     err.multipart_suggestion(msg, sugg, Applicability::MaybeIncorrect);

compiler/rustc_monomorphize/src/collector.rs

@@ -651,8 +651,8 @@ fn check_type_length_limit<'tcx>(tcx: TyCtxt<'tcx>, instance: Instance<'tcx>) {
         let (shrunk, written_to_path) = shrunk_instance_name(tcx, &instance);
         let span = tcx.def_span(instance.def_id());
         let mut path = PathBuf::new();
-        let was_written = if written_to_path.is_some() {
-            path = written_to_path.unwrap();
+        let was_written = if let Some(path2) = written_to_path {
+            path = path2;
             Some(())
         } else {
             None

compiler/rustc_span/src/hygiene.rs

@@ -109,7 +109,7 @@ fn assert_default_hashing_controls<CTX: HashStableContext>(ctx: &CTX, msg: &str)
         // This is the case for instance when building a hash for name mangling.
         // Such configuration must not be used for metadata.
         HashingControls { hash_spans }
-            if hash_spans == !ctx.unstable_opts_incremental_ignore_spans() => {}
+            if hash_spans != ctx.unstable_opts_incremental_ignore_spans() => {}
         other => panic!("Attempted hashing of {msg} with non-default HashingControls: {other:?}"),
     }
 }

compiler/rustc_trait_selection/src/traits/error_reporting/suggestions.rs

@@ -3888,8 +3888,7 @@ impl<'tcx> TypeErrCtxtExt<'tcx> for TypeErrCtxt<'_, 'tcx> {
         if let Some(slice_ty) = candidate_impls
             .iter()
             .map(|trait_ref| trait_ref.trait_ref.self_ty())
-            .filter(|t| is_slice(*t))
-            .next()
+            .find(|t| is_slice(*t))
         {
             let msg = &format!("convert the array to a `{}` slice instead", slice_ty);
 
@@ -3936,7 +3935,7 @@ fn hint_missing_borrow<'tcx>(
     // This could be a variant constructor, for example.
     let Some(fn_decl) = found_node.fn_decl() else { return; };
 
-    let args = fn_decl.inputs.iter().map(|ty| ty);
+    let args = fn_decl.inputs.iter();
 
     fn get_deref_type_and_refs(mut ty: Ty<'_>) -> (Ty<'_>, Vec<hir::Mutability>) {
         let mut refs = vec![];

src/librustdoc/config.rs

@@ -31,18 +31,13 @@ use crate::passes::{self, Condition};
 use crate::scrape_examples::{AllCallLocations, ScrapeExamplesOptions};
 use crate::theme;
 
-#[derive(Clone, Copy, PartialEq, Eq, Debug)]
+#[derive(Clone, Copy, PartialEq, Eq, Debug, Default)]
 pub(crate) enum OutputFormat {
     Json,
+    #[default]
     Html,
 }
 
-impl Default for OutputFormat {
-    fn default() -> OutputFormat {
-        OutputFormat::Html
-    }
-}
-
 impl OutputFormat {
     pub(crate) fn is_json(&self) -> bool {
         matches!(self, OutputFormat::Json)

src/librustdoc/html/highlight.rs

@@ -177,8 +177,8 @@ impl<'a, 'tcx, F: Write> TokenHandler<'a, 'tcx, F> {
         } else {
             // We only want to "open" the tag ourselves if we have more than one pending and if the
             // current parent tag is not the same as our pending content.
-            let close_tag = if self.pending_elems.len() > 1 && current_class.is_some() {
-                Some(enter_span(self.out, current_class.unwrap(), &self.href_context))
+            let close_tag = if self.pending_elems.len() > 1 && let Some(current_class) = current_class {
+                Some(enter_span(self.out, current_class, &self.href_context))
             } else {
                 None
             };

src/librustdoc/html/render/sidebar.rs

@@ -113,11 +113,8 @@ pub(super) fn print_sidebar(cx: &Context<'_>, it: &clean::Item, buffer: &mut Buf
     } else {
         ("", "")
     };
-    let version = if it.is_crate() {
-        cx.cache().crate_version.as_ref().map(String::as_str).unwrap_or_default()
-    } else {
-        ""
-    };
+    let version =
+        if it.is_crate() { cx.cache().crate_version.as_deref().unwrap_or_default() } else { "" };
     let path: String = if !it.is_mod() {
         cx.current.iter().map(|s| s.as_str()).intersperse("::").collect()
     } else {

src/librustdoc/passes/collect_intra_doc_links.rs

@@ -810,7 +810,7 @@ fn trait_impls_for<'a>(
 ///
 /// These are common and we should just resolve to the trait in that case.
 fn is_derive_trait_collision<T>(ns: &PerNS<Result<Vec<(Res, T)>, ResolutionFailure<'_>>>) -> bool {
-    if let (&Ok(ref type_ns), &Ok(ref macro_ns)) = (&ns.type_ns, &ns.macro_ns) {
+    if let (Ok(type_ns), Ok(macro_ns)) = (&ns.type_ns, &ns.macro_ns) {
         type_ns.iter().any(|(res, _)| matches!(res, Res::Def(DefKind::Trait, _)))
             && macro_ns
                 .iter()