clippy::complexity fixes

 filter_map_identity
 needless_bool
 search_is_some
 unit_arg
 map_identity
 needless_question_mark
 derivable_impls

compiler/rustc_const_eval/src/interpret/visitor.rs

@@ -21,7 +21,7 @@ pub trait ValueVisitor<'mir, 'tcx: 'mir, M: Machine<'mir, 'tcx>>: Sized {
     /// `read_discriminant` can be hooked for better error messages.
     #[inline(always)]
     fn read_discriminant(&mut self, v: &Self::V) -> InterpResult<'tcx, VariantIdx> {
-        Ok(self.ecx().read_discriminant(&v.to_op(self.ecx())?)?)
+        self.ecx().read_discriminant(&v.to_op(self.ecx())?)
     }
 
     /// This function provides the chance to reorder the order in which fields are visited for

compiler/rustc_driver_impl/src/lib.rs

@@ -587,10 +587,8 @@ fn show_md_content_with_pager(content: &str, color: ColorConfig) {
     let mut print_formatted = if pager_name == "less" {
         cmd.arg("-r");
         true
-    } else if ["bat", "catbat", "delta"].iter().any(|v| *v == pager_name) {
-        true
     } else {
-        false
+        ["bat", "catbat", "delta"].iter().any(|v| *v == pager_name)
     };
 
     if color == ColorConfig::Never {

compiler/rustc_hir_analysis/src/collect/item_bounds.rs

@@ -34,17 +34,14 @@ fn associated_type_bounds<'tcx>(
     let trait_def_id = tcx.local_parent(assoc_item_def_id);
     let trait_predicates = tcx.trait_explicit_predicates_and_bounds(trait_def_id);
 
-    let bounds_from_parent = trait_predicates
-        .predicates
-        .iter()
-        .copied()
-        .filter(|(pred, _)| match pred.kind().skip_binder() {
+    let bounds_from_parent = trait_predicates.predicates.iter().copied().filter(|(pred, _)| {
+        match pred.kind().skip_binder() {
             ty::ClauseKind::Trait(tr) => tr.self_ty() == item_ty,
             ty::ClauseKind::Projection(proj) => proj.projection_ty.self_ty() == item_ty,
             ty::ClauseKind::TypeOutlives(outlives) => outlives.0 == item_ty,
             _ => false,
-        })
-        .map(|(clause, span)| (clause, span));
+        }
+    });
 
     let all_bounds = tcx.arena.alloc_from_iter(bounds.clauses().chain(bounds_from_parent));
     debug!(

compiler/rustc_hir_typeck/src/upvar.rs

@@ -315,11 +315,8 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
         let final_tupled_upvars_type = Ty::new_tup(self.tcx, &final_upvar_tys);
         self.demand_suptype(span, args.tupled_upvars_ty(), final_tupled_upvars_type);
 
-        let fake_reads = delegate
-            .fake_reads
-            .into_iter()
-            .map(|(place, cause, hir_id)| (place, cause, hir_id))
-            .collect();
+        let fake_reads = delegate.fake_reads;
+
         self.typeck_results.borrow_mut().closure_fake_reads.insert(closure_def_id, fake_reads);
 
         if self.tcx.sess.opts.unstable_opts.profile_closures {

compiler/rustc_mir_transform/src/jump_threading.rs

@@ -649,7 +649,7 @@ impl OpportunitySet {
 
             // `succ` must be a successor of `current`. If it is not, this means this TO is not
             // satisfiable and a previous TO erased this edge, so we bail out.
-            if basic_blocks[current].terminator().successors().find(|s| *s == succ).is_none() {
+            if !basic_blocks[current].terminator().successors().any(|s| s == succ) {
                 debug!("impossible");
                 return;
             }

compiler/rustc_query_system/src/dep_graph/serialized.rs

@@ -70,7 +70,7 @@ const DEP_NODE_PAD: usize = DEP_NODE_SIZE - 1;
 const DEP_NODE_WIDTH_BITS: usize = DEP_NODE_SIZE / 2;
 
 /// Data for use when recompiling the **current crate**.
-#[derive(Debug)]
+#[derive(Debug, Default)]
 pub struct SerializedDepGraph {
     /// The set of all DepNodes in the graph
     nodes: IndexVec<SerializedDepNodeIndex, DepNode>,
@@ -89,18 +89,6 @@ pub struct SerializedDepGraph {
     index: Vec<UnhashMap<PackedFingerprint, SerializedDepNodeIndex>>,
 }
 
-impl Default for SerializedDepGraph {
-    fn default() -> Self {
-        SerializedDepGraph {
-            nodes: Default::default(),
-            fingerprints: Default::default(),
-            edge_list_indices: Default::default(),
-            edge_list_data: Default::default(),
-            index: Default::default(),
-        }
-    }
-}
-
 impl SerializedDepGraph {
     #[inline]
     pub fn edge_targets_from(

compiler/rustc_smir/src/rustc_smir/context.rs

@@ -157,7 +157,7 @@ impl<'tcx> Context for TablesWrapper<'tcx> {
                 (name == crate_name).then(|| smir_crate(tables.tcx, *crate_num))
             })
             .into_iter()
-            .filter_map(|c| c)
+            .flatten()
             .collect();
         crates
     }

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

@@ -1069,7 +1069,7 @@ impl<'tcx> TypeErrCtxtExt<'tcx> for TypeErrCtxt<'_, 'tcx> {
             if !self.tcx.is_diagnostic_item(sym::Result, def.did()) {
                 return None;
             }
-            Some(arg.as_type()?)
+            arg.as_type()
         };
 
         let mut suggested = false;

src/librustdoc/html/render/type_layout.rs

@@ -79,6 +79,7 @@ pub(crate) fn document_type_layout<'a, 'cx: 'a>(
             TypeLayoutSize { is_unsized, is_uninhabited, size }
         });
 
-        Ok(TypeLayout { variants, type_layout_size }.render_into(f).unwrap())
+        TypeLayout { variants, type_layout_size }.render_into(f).unwrap();
+        Ok(())
     })
 }