clippy fixes for librustdoc

fixes clippy warnings of type:
match_like_matches_macro
or_fun_call
op_ref
needless_return
let_and_return
single_char_add_str
useless_format
unnecessary_sort_by
match_ref_pats
redundant_field_names

src/librustdoc/clean/auto_trait.rs

@@ -738,11 +738,11 @@ impl<'a, 'tcx> AutoTraitFinder<'a, 'tcx> {
     }
 
     fn is_fn_ty(&self, tcx: TyCtxt<'_>, ty: &Type) -> bool {
-        match &ty {
-            &&Type::ResolvedPath { ref did, .. } => {
-                *did == tcx.require_lang_item(LangItem::Fn, None)
-                    || *did == tcx.require_lang_item(LangItem::FnMut, None)
-                    || *did == tcx.require_lang_item(LangItem::FnOnce, None)
+        match ty {
+            &Type::ResolvedPath { did, .. } => {
+                did == tcx.require_lang_item(LangItem::Fn, None)
+                    || did == tcx.require_lang_item(LangItem::FnMut, None)
+                    || did == tcx.require_lang_item(LangItem::FnOnce, None)
             }
             _ => false,
         }

src/librustdoc/clean/cfg.rs

@@ -177,10 +177,7 @@ impl Cfg {
             Cfg::Any(ref sub_cfgs) | Cfg::All(ref sub_cfgs) => {
                 sub_cfgs.first().map(Cfg::should_capitalize_first_letter).unwrap_or(false)
             }
-            Cfg::Cfg(name, _) => match name {
-                sym::debug_assertions | sym::target_endian => true,
-                _ => false,
-            },
+            Cfg::Cfg(name, _) => name == sym::debug_assertions || name == sym::target_endian,
         }
     }
 
@@ -188,18 +185,13 @@ impl Cfg {
         match *self {
             Cfg::False | Cfg::True => false,
             Cfg::Any(..) | Cfg::All(..) | Cfg::Cfg(..) => true,
-            Cfg::Not(ref child) => match **child {
-                Cfg::Cfg(..) => true,
-                _ => false,
-            },
+            Cfg::Not(box Cfg::Cfg(..)) => true,
+            Cfg::Not(..) => false,
         }
     }
 
     fn should_use_with_in_description(&self) -> bool {
-        match *self {
-            Cfg::Cfg(name, _) if name == sym::target_feature => true,
-            _ => false,
-        }
+        matches!(self, Cfg::Cfg(sym::target_feature, _))
     }
 
     /// Attempt to simplify this cfg by assuming that `assume` is already known to be true, will

src/librustdoc/clean/mod.rs

@@ -640,10 +640,10 @@ impl Clean<Generics> for hir::Generics<'_> {
         ///
         /// [`lifetime_to_generic_param`]: rustc_ast_lowering::LoweringContext::lifetime_to_generic_param
         fn is_elided_lifetime(param: &hir::GenericParam<'_>) -> bool {
-            match param.kind {
-                hir::GenericParamKind::Lifetime { kind: hir::LifetimeParamKind::Elided } => true,
-                _ => false,
-            }
+            matches!(
+                param.kind,
+                hir::GenericParamKind::Lifetime { kind: hir::LifetimeParamKind::Elided }
+            )
         }
 
         let impl_trait_params = self
@@ -801,7 +801,7 @@ impl<'a, 'tcx> Clean<Generics> for (&'a ty::Generics, ty::GenericPredicates<'tcx
 
         for (param, mut bounds) in impl_trait {
             // Move trait bounds to the front.
-            bounds.sort_by_key(|b| if let GenericBound::TraitBound(..) = b { false } else { true });
+            bounds.sort_by_key(|b| !matches!(b, GenericBound::TraitBound(..)));
 
             if let crate::core::ImplTraitParam::ParamIndex(idx) = param {
                 if let Some(proj) = impl_trait_proj.remove(&idx) {

src/librustdoc/clean/types.rs

@@ -175,11 +175,9 @@ impl Item {
     }
 
     crate fn is_crate(&self) -> bool {
-        match *self.kind {
+        matches!(*self.kind,
             StrippedItem(box ModuleItem(Module { is_crate: true, .. }))
-            | ModuleItem(Module { is_crate: true, .. }) => true,
-            _ => false,
-        }
+            | ModuleItem(Module { is_crate: true, .. }))
     }
     crate fn is_mod(&self) -> bool {
         self.type_() == ItemType::Module
@@ -378,10 +376,7 @@ impl ItemKind {
     }
 
     crate fn is_type_alias(&self) -> bool {
-        match *self {
-            ItemKind::TypedefItem(_, _) | ItemKind::AssocTypeItem(_, _) => true,
-            _ => false,
-        }
+        matches!(self, ItemKind::TypedefItem(..) | ItemKind::AssocTypeItem(..))
     }
 }
 
@@ -674,7 +669,7 @@ impl Attributes {
                                 span: attr.span,
                                 doc: contents,
                                 kind: DocFragmentKind::Include { filename },
-                                parent_module: parent_module,
+                                parent_module,
                             });
                         }
                     }
@@ -750,7 +745,7 @@ impl Attributes {
                     Some(did) => {
                         if let Some((mut href, ..)) = href(did) {
                             if let Some(ref fragment) = *fragment {
-                                href.push_str("#");
+                                href.push('#');
                                 href.push_str(fragment);
                             }
                             Some(RenderedLink {
@@ -945,10 +940,7 @@ crate enum GenericParamDefKind {
 
 impl GenericParamDefKind {
     crate fn is_type(&self) -> bool {
-        match *self {
-            GenericParamDefKind::Type { .. } => true,
-            _ => false,
-        }
+        matches!(self, GenericParamDefKind::Type { .. })
     }
 
     // FIXME(eddyb) this either returns the default of a type parameter, or the
@@ -1292,15 +1284,12 @@ impl Type {
     }
 
     crate fn is_full_generic(&self) -> bool {
-        match *self {
-            Type::Generic(_) => true,
-            _ => false,
-        }
+        matches!(self, Type::Generic(_))
     }
 
     crate fn projection(&self) -> Option<(&Type, DefId, Symbol)> {
         let (self_, trait_, name) = match self {
-            QPath { ref self_type, ref trait_, name } => (self_type, trait_, name),
+            QPath { self_type, trait_, name } => (self_type, trait_, name),
             _ => return None,
         };
         let trait_did = match **trait_ {

src/librustdoc/config.rs

@@ -37,10 +37,7 @@ crate enum OutputFormat {
 
 impl OutputFormat {
     crate fn is_json(&self) -> bool {
-        match self {
-            OutputFormat::Json => true,
-            _ => false,
-        }
+        matches!(self, OutputFormat::Json)
     }
 }
 

src/librustdoc/doctest.rs

@@ -636,15 +636,15 @@ fn partition_source(s: &str) -> (String, String, String) {
         match state {
             PartitionState::Attrs => {
                 before.push_str(line);
-                before.push_str("\n");
+                before.push('\n');
             }
             PartitionState::Crates => {
                 crates.push_str(line);
-                crates.push_str("\n");
+                crates.push('\n');
             }
             PartitionState::Other => {
                 after.push_str(line);
-                after.push_str("\n");
+                after.push('\n');
             }
         }
     }

src/librustdoc/fold.rs

@@ -61,7 +61,7 @@ crate trait DocFolder: Sized {
                         j.fields = j.fields.into_iter().filter_map(|x| self.fold_item(x)).collect();
                         j.fields_stripped |= num_fields != j.fields.len()
                             || j.fields.iter().any(|f| f.is_stripped());
-                        VariantItem(Variant { kind: VariantKind::Struct(j), ..i2 })
+                        VariantItem(Variant { kind: VariantKind::Struct(j) })
                     }
                     _ => VariantItem(i2),
                 }

src/librustdoc/html/format.rs

@@ -245,7 +245,7 @@ impl<'a> fmt::Display for WhereClause<'a> {
             }
 
             match pred {
-                &clean::WherePredicate::BoundPredicate { ref ty, ref bounds } => {
+                clean::WherePredicate::BoundPredicate { ty, bounds } => {
                     let bounds = bounds;
                     if f.alternate() {
                         clause.push_str(&format!(
@@ -261,7 +261,7 @@ impl<'a> fmt::Display for WhereClause<'a> {
                         ));
                     }
                 }
-                &clean::WherePredicate::RegionPredicate { ref lifetime, ref bounds } => {
+                clean::WherePredicate::RegionPredicate { lifetime, bounds } => {
                     clause.push_str(&format!(
                         "{}: {}",
                         lifetime.print(),
@@ -272,7 +272,7 @@ impl<'a> fmt::Display for WhereClause<'a> {
                             .join(" + ")
                     ));
                 }
-                &clean::WherePredicate::EqPredicate { ref lhs, ref rhs } => {
+                clean::WherePredicate::EqPredicate { lhs, rhs } => {
                     if f.alternate() {
                         clause.push_str(&format!("{:#} == {:#}", lhs.print(), rhs.print()));
                     } else {
@@ -376,8 +376,8 @@ impl clean::GenericBound {
 impl clean::GenericArgs {
     fn print(&self) -> impl fmt::Display + '_ {
         display_fn(move |f| {
-            match *self {
-                clean::GenericArgs::AngleBracketed { ref args, ref bindings } => {
+            match self {
+                clean::GenericArgs::AngleBracketed { args, bindings } => {
                     if !args.is_empty() || !bindings.is_empty() {
                         if f.alternate() {
                             f.write_str("<")?;
@@ -414,7 +414,7 @@ impl clean::GenericArgs {
                         }
                     }
                 }
-                clean::GenericArgs::Parenthesized { ref inputs, ref output } => {
+                clean::GenericArgs::Parenthesized { inputs, output } => {
                     f.write_str("(")?;
                     let mut comma = false;
                     for ty in inputs {
@@ -501,7 +501,7 @@ crate fn href(did: DefId) -> Option<(String, ItemType, Vec<String>)> {
     };
     for component in &fqp[..fqp.len() - 1] {
         url.push_str(component);
-        url.push_str("/");
+        url.push('/');
     }
     match shortty {
         ItemType::Module => {
@@ -510,7 +510,7 @@ crate fn href(did: DefId) -> Option<(String, ItemType, Vec<String>)> {
         }
         _ => {
             url.push_str(shortty.as_str());
-            url.push_str(".");
+            url.push('.');
             url.push_str(fqp.last().unwrap());
             url.push_str(".html");
         }
@@ -1021,7 +1021,7 @@ impl Function<'_> {
                 } else {
                     if i > 0 {
                         args.push_str(" <br>");
-                        args_plain.push_str(" ");
+                        args_plain.push(' ');
                     }
                     if !input.name.is_empty() {
                         args.push_str(&format!("{}: ", input.name));

src/librustdoc/html/markdown.rs

@@ -489,15 +489,10 @@ impl<'a, I: Iterator<Item = Event<'a>>> SummaryLine<'a, I> {
 }
 
 fn check_if_allowed_tag(t: &Tag<'_>) -> bool {
-    match *t {
-        Tag::Paragraph
-        | Tag::Item
-        | Tag::Emphasis
-        | Tag::Strong
-        | Tag::Link(..)
-        | Tag::BlockQuote => true,
-        _ => false,
-    }
+    matches!(
+        t,
+        Tag::Paragraph | Tag::Item | Tag::Emphasis | Tag::Strong | Tag::Link(..) | Tag::BlockQuote
+    )
 }
 
 impl<'a, I: Iterator<Item = Event<'a>>> Iterator for SummaryLine<'a, I> {

src/librustdoc/html/render/mod.rs

@@ -979,7 +979,7 @@ themePicker.onblur = handleThemeButtonsBlur;
                 .iter()
                 .map(|s| format!("\"{}\"", s.to_str().expect("invalid osstring conversion")))
                 .collect::<Vec<_>>();
-            files.sort_unstable_by(|a, b| a.cmp(b));
+            files.sort_unstable();
             let subs = subs.iter().map(|s| s.to_json_string()).collect::<Vec<_>>().join(",");
             let dirs =
                 if subs.is_empty() { String::new() } else { format!(",\"dirs\":[{}]", subs) };
@@ -1428,7 +1428,7 @@ impl Setting {
                     .map(|opt| format!(
                         "<option value=\"{}\" {}>{}</option>",
                         opt.0,
-                        if &opt.0 == default_value { "selected" } else { "" },
+                        if opt.0 == default_value { "selected" } else { "" },
                         opt.1,
                     ))
                     .collect::<String>(),
@@ -1595,7 +1595,7 @@ impl Context<'_> {
             if let Some(&(ref names, ty)) = cache.paths.get(&it.def_id) {
                 for name in &names[..names.len() - 1] {
                     url.push_str(name);
-                    url.push_str("/");
+                    url.push('/');
                 }
                 url.push_str(&item_path(ty, names.last().unwrap()));
                 layout::redirect(&url)
@@ -2308,7 +2308,7 @@ fn short_item_info(
             let since = &since.as_str();
             if !stability::deprecation_in_effect(is_since_rustc_version, Some(since)) {
                 if *since == "TBD" {
-                    format!("Deprecating in a future Rust version")
+                    String::from("Deprecating in a future Rust version")
                 } else {
                     format!("Deprecating in {}", Escape(since))
                 }
@@ -4323,9 +4323,11 @@ fn sidebar_assoc_items(it: &clean::Item) -> String {
                         .any(|i| i.inner_impl().trait_.def_id() == c.deref_mut_trait_did);
                     let inner_impl = target
                         .def_id()
-                        .or(target
-                            .primitive_type()
-                            .and_then(|prim| c.primitive_locations.get(&prim).cloned()))
+                        .or_else(|| {
+                            target
+                                .primitive_type()
+                                .and_then(|prim| c.primitive_locations.get(&prim).cloned())
+                        })
                         .and_then(|did| c.impls.get(&did));
                     if let Some(impls) = inner_impl {
                         out.push_str("<a class=\"sidebar-title\" href=\"#deref-methods\">");

src/librustdoc/html/toc.rs

@@ -132,7 +132,7 @@ impl TocBuilder {
                 }
                 Some(entry) => {
                     sec_number = entry.sec_number.clone();
-                    sec_number.push_str(".");
+                    sec_number.push('.');
                     (entry.level, &entry.children)
                 }
             };

src/librustdoc/passes/collect_intra_doc_links.rs

@@ -1276,7 +1276,7 @@ impl LinkCollector<'_, '_> {
                         // This could just be a normal link or a broken link
                         // we could potentially check if something is
                         // "intra-doc-link-like" and warn in that case.
-                        return None;
+                        None
                     }
                     Err(ErrorKind::AnchorFailure(msg)) => {
                         anchor_failure(
@@ -1287,7 +1287,7 @@ impl LinkCollector<'_, '_> {
                             diag.link_range,
                             msg,
                         );
-                        return None;
+                        None
                     }
                 }
             }
@@ -1383,7 +1383,7 @@ impl LinkCollector<'_, '_> {
                         diag.link_range,
                         candidates.present_items().collect(),
                     );
-                    return None;
+                    None
                 }
             }
             Some(MacroNS) => {
@@ -1408,7 +1408,7 @@ impl LinkCollector<'_, '_> {
                             diag.link_range,
                             smallvec![kind],
                         );
-                        return None;
+                        None
                     }
                 }
             }

src/librustdoc/passes/html_tags.rs

@@ -59,7 +59,7 @@ fn drop_tag(
                 continue;
             }
             let last_tag_name_low = last_tag_name.to_lowercase();
-            if ALLOWED_UNCLOSED.iter().any(|&at| at == &last_tag_name_low) {
+            if ALLOWED_UNCLOSED.iter().any(|&at| at == last_tag_name_low) {
                 continue;
             }
             // `tags` is used as a queue, meaning that everything after `pos` is included inside it.

src/librustdoc/passes/strip_hidden.rs

@@ -26,9 +26,7 @@ crate fn strip_hidden(krate: clean::Crate, _: &DocContext<'_>) -> clean::Crate {
 
     // strip all impls referencing stripped items
     let mut stripper = ImplStripper { retained: &retained };
-    let krate = stripper.fold_crate(krate);
-
-    krate
+    stripper.fold_crate(krate)
 }
 
 struct Stripper<'a> {

src/librustdoc/theme.rs

@@ -70,15 +70,12 @@ impl Events {
     }
 
     fn is_comment(&self) -> bool {
-        match *self {
-            Events::StartLineComment(_) | Events::StartComment(_) | Events::EndComment(_) => true,
-            _ => false,
-        }
+        matches!(self, Events::StartLineComment(_) | Events::StartComment(_) | Events::EndComment(_))
     }
 }
 
 fn previous_is_line_comment(events: &[Events]) -> bool {
-    if let Some(&Events::StartLineComment(_)) = events.last() { true } else { false }
+    matches!(events.last(), Some(&Events::StartLineComment(_)))
 }
 
 fn is_line_comment(pos: usize, v: &[u8], events: &[Events]) -> bool {