reduce borrowing and (de)referencing around match patterns (clippy::m…

…atch_ref_pats)

compiler/rustc_ast/src/ast.rs

@@ -433,9 +433,9 @@ pub enum WherePredicate {
 impl WherePredicate {
     pub fn span(&self) -> Span {
         match self {
-            &WherePredicate::BoundPredicate(ref p) => p.span,
-            &WherePredicate::RegionPredicate(ref p) => p.span,
-            &WherePredicate::EqPredicate(ref p) => p.span,
+            WherePredicate::BoundPredicate(p) => p.span,
+            WherePredicate::RegionPredicate(p) => p.span,
+            WherePredicate::EqPredicate(p) => p.span,
         }
     }
 }

compiler/rustc_ast_passes/src/ast_validation.rs

@@ -1212,11 +1212,11 @@ impl<'a> Visitor<'a> for AstValidator<'a> {
     }
 
     fn visit_pat(&mut self, pat: &'a Pat) {
-        match pat.kind {
-            PatKind::Lit(ref expr) => {
+        match &pat.kind {
+            PatKind::Lit(expr) => {
                 self.check_expr_within_pat(expr, false);
             }
-            PatKind::Range(ref start, ref end, _) => {
+            PatKind::Range(start, end, _) => {
                 if let Some(expr) = start {
                     self.check_expr_within_pat(expr, true);
                 }

compiler/rustc_builtin_macros/src/deriving/hash.rs

@@ -48,8 +48,8 @@ pub fn expand_deriving_hash(
 }
 
 fn hash_substructure(cx: &mut ExtCtxt<'_>, trait_span: Span, substr: &Substructure<'_>) -> P<Expr> {
-    let state_expr = match &substr.nonself_args {
-        &[o_f] => o_f,
+    let state_expr = match substr.nonself_args {
+        [o_f] => o_f,
         _ => cx.span_bug(trait_span, "incorrect number of arguments in `derive(Hash)`"),
     };
     let call_hash = |span, thing_expr| {
@@ -64,9 +64,9 @@ fn hash_substructure(cx: &mut ExtCtxt<'_>, trait_span: Span, substr: &Substructu
     };
     let mut stmts = Vec::new();
 
-    let fields = match *substr.fields {
-        Struct(_, ref fs) | EnumMatching(_, 1, .., ref fs) => fs,
-        EnumMatching(.., ref fs) => {
+    let fields = match substr.fields {
+        Struct(_, fs) | EnumMatching(_, 1, .., fs) => fs,
+        EnumMatching(.., fs) => {
             let variant_value = deriving::call_intrinsic(
                 cx,
                 trait_span,

compiler/rustc_hir/src/hir.rs

@@ -378,9 +378,9 @@ impl GenericBound<'_> {
 
     pub fn span(&self) -> Span {
         match self {
-            &GenericBound::Trait(ref t, ..) => t.span,
-            &GenericBound::LangItemTrait(_, span, ..) => span,
-            &GenericBound::Outlives(ref l) => l.span,
+            GenericBound::Trait(t, ..) => t.span,
+            GenericBound::LangItemTrait(_, span, ..) => *span,
+            GenericBound::Outlives(l) => l.span,
         }
     }
 }
@@ -538,9 +538,9 @@ pub enum WherePredicate<'hir> {
 impl WherePredicate<'_> {
     pub fn span(&self) -> Span {
         match self {
-            &WherePredicate::BoundPredicate(ref p) => p.span,
-            &WherePredicate::RegionPredicate(ref p) => p.span,
-            &WherePredicate::EqPredicate(ref p) => p.span,
+            WherePredicate::BoundPredicate(p) => p.span,
+            WherePredicate::RegionPredicate(p) => p.span,
+            WherePredicate::EqPredicate(p) => p.span,
         }
     }
 }

compiler/rustc_hir/src/intravisit.rs

@@ -896,8 +896,8 @@ pub fn walk_where_predicate<'v, V: Visitor<'v>>(
     visitor: &mut V,
     predicate: &'v WherePredicate<'v>,
 ) {
-    match predicate {
-        &WherePredicate::BoundPredicate(WhereBoundPredicate {
+    match *predicate {
+        WherePredicate::BoundPredicate(WhereBoundPredicate {
             ref bounded_ty,
             bounds,
             bound_generic_params,
@@ -907,11 +907,11 @@ pub fn walk_where_predicate<'v, V: Visitor<'v>>(
             walk_list!(visitor, visit_param_bound, bounds);
             walk_list!(visitor, visit_generic_param, bound_generic_params);
         }
-        &WherePredicate::RegionPredicate(WhereRegionPredicate { ref lifetime, bounds, .. }) => {
+        WherePredicate::RegionPredicate(WhereRegionPredicate { ref lifetime, bounds, .. }) => {
             visitor.visit_lifetime(lifetime);
             walk_list!(visitor, visit_param_bound, bounds);
         }
-        &WherePredicate::EqPredicate(WhereEqPredicate {
+        WherePredicate::EqPredicate(WhereEqPredicate {
             hir_id, ref lhs_ty, ref rhs_ty, ..
         }) => {
             visitor.visit_id(hir_id);

compiler/rustc_hir_pretty/src/lib.rs

@@ -2233,19 +2233,19 @@ impl<'a> State<'a> {
             }
 
             match predicate {
-                &hir::WherePredicate::BoundPredicate(hir::WhereBoundPredicate {
-                    ref bound_generic_params,
-                    ref bounded_ty,
+                hir::WherePredicate::BoundPredicate(hir::WhereBoundPredicate {
+                    bound_generic_params,
+                    bounded_ty,
                     bounds,
                     ..
                 }) => {
                     self.print_formal_generic_params(bound_generic_params);
                     self.print_type(&bounded_ty);
-                    self.print_bounds(":", bounds);
+                    self.print_bounds(":", *bounds);
                 }
-                &hir::WherePredicate::RegionPredicate(hir::WhereRegionPredicate {
-                    ref lifetime,
-                    ref bounds,
+                hir::WherePredicate::RegionPredicate(hir::WhereRegionPredicate {
+                    lifetime,
+                    bounds,
                     ..
                 }) => {
                     self.print_lifetime(lifetime);
@@ -2264,10 +2264,8 @@ impl<'a> State<'a> {
                         }
                     }
                 }
-                &hir::WherePredicate::EqPredicate(hir::WhereEqPredicate {
-                    ref lhs_ty,
-                    ref rhs_ty,
-                    ..
+                hir::WherePredicate::EqPredicate(hir::WhereEqPredicate {
+                    lhs_ty, rhs_ty, ..
                 }) => {
                     self.print_type(lhs_ty);
                     self.s.space();

compiler/rustc_incremental/src/assert_dep_graph.rs

@@ -310,13 +310,13 @@ fn filter_nodes<'q>(
     sources: &Option<FxHashSet<&'q DepNode>>,
     targets: &Option<FxHashSet<&'q DepNode>>,
 ) -> FxHashSet<&'q DepNode> {
-    if let &Some(ref sources) = sources {
-        if let &Some(ref targets) = targets {
+    if let Some(sources) = sources {
+        if let Some(targets) = targets {
             walk_between(query, sources, targets)
         } else {
             walk_nodes(query, sources, OUTGOING)
         }
-    } else if let &Some(ref targets) = targets {
+    } else if let Some(targets) = targets {
         walk_nodes(query, targets, INCOMING)
     } else {
         query.nodes().into_iter().collect()

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

@@ -915,7 +915,7 @@ impl<'a, 'tcx> InferCtxt<'a, 'tcx> {
                 self.highlight_outer(&mut t1_out, &mut t2_out, path, sub, i, &other_ty);
                 return Some(());
             }
-            if let &ty::Adt(def, _) = ta.kind() {
+            if let ty::Adt(def, _) = ta.kind() {
                 let path_ = self.tcx.def_path_str(def.did);
                 if path_ == other_path {
                     self.highlight_outer(&mut t1_out, &mut t2_out, path, sub, i, &other_ty);

compiler/rustc_lint/src/builtin.rs

@@ -938,8 +938,8 @@ impl EarlyLintPass for DeprecatedAttr {
             if attr.ident().map(|ident| ident.name) == Some(n) {
                 if let &AttributeGate::Gated(
                     Stability::Deprecated(link, suggestion),
-                    ref name,
-                    ref reason,
+                    name,
+                    reason,
                     _,
                 ) = g
                 {

compiler/rustc_lint/src/nonstandard_style.rs

@@ -397,7 +397,7 @@ impl<'tcx> LateLintPass<'tcx> for NonSnakeCase {
     }
 
     fn check_pat(&mut self, cx: &LateContext<'_>, p: &hir::Pat<'_>) {
-        if let &PatKind::Binding(_, hid, ident, _) = &p.kind {
+        if let PatKind::Binding(_, hid, ident, _) = p.kind {
             if let hir::Node::Pat(parent_pat) = cx.tcx.hir().get(cx.tcx.hir().get_parent_node(hid))
             {
                 if let PatKind::Struct(_, field_pats, _) = &parent_pat.kind {

compiler/rustc_lint/src/unused.rs

@@ -862,11 +862,11 @@ impl EarlyLintPass for UnusedParens {
     }
 
     fn check_ty(&mut self, cx: &EarlyContext<'_>, ty: &ast::Ty) {
-        if let &ast::TyKind::Paren(ref r) = &ty.kind {
+        if let ast::TyKind::Paren(r) = &ty.kind {
             match &r.kind {
-                &ast::TyKind::TraitObject(..) => {}
-                &ast::TyKind::ImplTrait(_, ref bounds) if bounds.len() > 1 => {}
-                &ast::TyKind::Array(_, ref len) => {
+                ast::TyKind::TraitObject(..) => {}
+                ast::TyKind::ImplTrait(_, bounds) if bounds.len() > 1 => {}
+                ast::TyKind::Array(_, len) => {
                     self.check_unused_delims_expr(
                         cx,
                         &len.value,

compiler/rustc_metadata/src/native_libs.rs

@@ -192,13 +192,13 @@ impl Collector<'tcx> {
     fn process_command_line(&mut self) {
         // First, check for errors
         let mut renames = FxHashSet::default();
-        for &(ref name, ref new_name, _) in &self.tcx.sess.opts.libs {
-            if let &Some(ref new_name) = new_name {
+        for (name, new_name, _) in &self.tcx.sess.opts.libs {
+            if let Some(ref new_name) = new_name {
                 let any_duplicate = self
                     .libs
                     .iter()
                     .filter_map(|lib| lib.name.as_ref())
-                    .any(|n| n.as_str() == *name);
+                    .any(|n| &n.as_str() == name);
                 if new_name.is_empty() {
                     self.tcx.sess.err(&format!(
                         "an empty renaming target was specified for library `{}`",
@@ -240,7 +240,7 @@ impl Collector<'tcx> {
                             if kind != NativeLibKind::Unspecified {
                                 lib.kind = kind;
                             }
-                            if let &Some(ref new_name) = new_name {
+                            if let Some(new_name) = new_name {
                                 lib.name = Some(Symbol::intern(new_name));
                             }
                             return true;

compiler/rustc_middle/src/ty/diagnostics.rs

@@ -245,8 +245,8 @@ pub fn suggest_constraining_type_param(
                 }
             }
 
-            match &param_spans[..] {
-                &[&param_span] => suggest_restrict(param_span.shrink_to_hi()),
+            match param_spans[..] {
+                [&param_span] => suggest_restrict(param_span.shrink_to_hi()),
                 _ => {
                     err.span_suggestion_verbose(
                         generics.where_clause.tail_span_for_suggestion(),

compiler/rustc_mir/src/borrow_check/diagnostics/move_errors.rs

@@ -302,7 +302,7 @@ impl<'a, 'tcx> MirBorrowckCtxt<'a, 'tcx> {
             .find_map(|p| self.is_upvar_field_projection(p));
 
         let deref_base = match deref_target_place.projection.as_ref() {
-            &[ref proj_base @ .., ProjectionElem::Deref] => {
+            [proj_base @ .., ProjectionElem::Deref] => {
                 PlaceRef { local: deref_target_place.local, projection: &proj_base }
             }
             _ => bug!("deref_target_place is not a deref projection"),

compiler/rustc_mir/src/borrow_check/type_check/mod.rs

@@ -1855,8 +1855,8 @@ impl<'a, 'tcx> TypeChecker<'a, 'tcx> {
                     self.assert_iscleanup(body, block_data, unwind, true);
                 }
             }
-            TerminatorKind::InlineAsm { ref destination, .. } => {
-                if let &Some(target) = destination {
+            TerminatorKind::InlineAsm { destination, .. } => {
+                if let Some(target) = destination {
                     self.assert_iscleanup(body, block_data, target, is_cleanup);
                 }
             }

compiler/rustc_passes/src/naked_functions.rs

@@ -149,7 +149,7 @@ impl<'tcx> Visitor<'tcx> for CheckParameters<'tcx> {
 fn check_asm<'tcx>(tcx: TyCtxt<'tcx>, hir_id: HirId, body: &'tcx hir::Body<'tcx>, fn_span: Span) {
     let mut this = CheckInlineAssembly { tcx, items: Vec::new() };
     this.visit_body(body);
-    if let &[(ItemKind::Asm, _)] = &this.items[..] {
+    if let [(ItemKind::Asm, _)] = this.items[..] {
         // Ok.
     } else {
         tcx.struct_span_lint_hir(UNSUPPORTED_NAKED_FUNCTIONS, hir_id, fn_span, |lint| {

compiler/rustc_save_analysis/src/dump_visitor.rs

@@ -582,7 +582,7 @@ impl<'tcx> DumpVisitor<'tcx> {
                 }
                 ref v => {
                     let mut value = format!("{}::{}", enum_data.name, name);
-                    if let &hir::VariantData::Tuple(ref fields, _) = v {
+                    if let hir::VariantData::Tuple(fields, _) = v {
                         value.push('(');
                         value.push_str(
                             &fields
@@ -653,7 +653,7 @@ impl<'tcx> DumpVisitor<'tcx> {
         let map = &self.tcx.hir();
         self.nest_typeck_results(map.local_def_id(item.hir_id), |v| {
             v.visit_ty(&typ);
-            if let &Some(ref trait_ref) = trait_ref {
+            if let Some(trait_ref) = trait_ref {
                 v.process_path(trait_ref.hir_ref_id, &hir::QPath::Resolved(None, &trait_ref.path));
             }
             v.process_generic_params(generics, "", item.hir_id);
@@ -1082,7 +1082,7 @@ impl<'tcx> DumpVisitor<'tcx> {
                     );
                 }
 
-                if let &Some(ref default_ty) = default_ty {
+                if let Some(default_ty) = default_ty {
                     self.visit_ty(default_ty)
                 }
             }

compiler/rustc_trait_selection/src/traits/auto_trait.rs

@@ -305,8 +305,8 @@ impl AutoTraitFinder<'tcx> {
                 infcx.resolve_vars_if_possible(Obligation::new(dummy_cause.clone(), new_env, pred));
             let result = select.select(&obligation);
 
-            match &result {
-                &Ok(Some(ref impl_source)) => {
+            match result {
+                Ok(Some(ref impl_source)) => {
                     // If we see an explicit negative impl (e.g., `impl !Send for MyStruct`),
                     // we immediately bail out, since it's impossible for us to continue.
 
@@ -339,8 +339,8 @@ impl AutoTraitFinder<'tcx> {
                         return None;
                     }
                 }
-                &Ok(None) => {}
-                &Err(SelectionError::Unimplemented) => {
+                Ok(None) => {}
+                Err(SelectionError::Unimplemented) => {
                     if self.is_param_no_infer(pred.skip_binder().trait_ref.substs) {
                         already_visited.remove(&pred);
                         self.add_user_pred(
@@ -863,7 +863,7 @@ impl<'a, 'tcx> TypeFolder<'tcx> for RegionReplacer<'a, 'tcx> {
 
     fn fold_region(&mut self, r: ty::Region<'tcx>) -> ty::Region<'tcx> {
         (match r {
-            &ty::ReVar(vid) => self.vid_to_region.get(&vid).cloned(),
+            ty::ReVar(vid) => self.vid_to_region.get(vid).cloned(),
             _ => None,
         })
         .unwrap_or_else(|| r.super_fold_with(self))

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

@@ -1368,7 +1368,7 @@ impl<'a, 'tcx> InferCtxtPrivExt<'tcx> for InferCtxt<'a, 'tcx> {
         code: &ObligationCauseCode<'tcx>,
     ) -> Option<(String, Option<Span>)> {
         match code {
-            &ObligationCauseCode::BuiltinDerivedObligation(ref data) => {
+            ObligationCauseCode::BuiltinDerivedObligation(data) => {
                 let parent_trait_ref = self.resolve_vars_if_possible(data.parent_trait_ref);
                 match self.get_parent_trait_ref(&data.parent_code) {
                     Some(t) => Some(t),

compiler/rustc_trait_selection/src/traits/select/mod.rs

@@ -69,16 +69,16 @@ impl IntercrateAmbiguityCause {
 
     pub fn intercrate_ambiguity_hint(&self) -> String {
         match self {
-            &IntercrateAmbiguityCause::DownstreamCrate { ref trait_desc, ref self_desc } => {
-                let self_desc = if let &Some(ref ty) = self_desc {
+            IntercrateAmbiguityCause::DownstreamCrate { trait_desc, self_desc } => {
+                let self_desc = if let Some(ty) = self_desc {
                     format!(" for type `{}`", ty)
                 } else {
                     String::new()
                 };
                 format!("downstream crates may implement trait `{}`{}", trait_desc, self_desc)
             }
-            &IntercrateAmbiguityCause::UpstreamCrateUpdate { ref trait_desc, ref self_desc } => {
-                let self_desc = if let &Some(ref ty) = self_desc {
+            IntercrateAmbiguityCause::UpstreamCrateUpdate { trait_desc, self_desc } => {
+                let self_desc = if let Some(ty) = self_desc {
                     format!(" for type `{}`", ty)
                 } else {
                     String::new()
@@ -89,7 +89,7 @@ impl IntercrateAmbiguityCause {
                     trait_desc, self_desc
                 )
             }
-            &IntercrateAmbiguityCause::ReservationImpl { ref message } => message.clone(),
+            IntercrateAmbiguityCause::ReservationImpl { message } => message.clone(),
         }
     }
 }

compiler/rustc_typeck/src/astconv/mod.rs

@@ -770,7 +770,7 @@ impl<'o, 'tcx> dyn AstConv<'tcx> + 'o {
         // Try to find an unbound in bounds.
         let mut unbound = None;
         for ab in ast_bounds {
-            if let &hir::GenericBound::Trait(ref ptr, hir::TraitBoundModifier::Maybe) = ab {
+            if let hir::GenericBound::Trait(ptr, hir::TraitBoundModifier::Maybe) = ab {
                 if unbound.is_none() {
                     unbound = Some(&ptr.trait_ref);
                 } else {

compiler/rustc_typeck/src/check/callee.rs

@@ -290,16 +290,16 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
             ty::FnPtr(sig) => (sig, None),
             ref t => {
                 let mut unit_variant = None;
-                if let &ty::Adt(adt_def, ..) = t {
+                if let ty::Adt(adt_def, ..) = t {
                     if adt_def.is_enum() {
-                        if let hir::ExprKind::Call(ref expr, _) = call_expr.kind {
+                        if let hir::ExprKind::Call(expr, _) = call_expr.kind {
                             unit_variant =
                                 self.tcx.sess.source_map().span_to_snippet(expr.span).ok();
                         }
                     }
                 }
 
-                if let hir::ExprKind::Call(ref callee, _) = call_expr.kind {
+                if let hir::ExprKind::Call(callee, _) = call_expr.kind {
                     let mut err = type_error_struct!(
                         self.tcx.sess,
                         callee.span,