Replace enum ==s with matches where it makes sense

compiler/rustc_ast/src/util/comments.rs

@@ -58,7 +58,8 @@ pub fn beautify_doc_string(data: Symbol, kind: CommentKind) -> Symbol {
         // In case we have doc comments like `/**` or `/*!`, we want to remove stars if they are
         // present. However, we first need to strip the empty lines so they don't get in the middle
         // when we try to compute the "horizontal trim".
-        let lines = if kind == CommentKind::Block {
+        let lines = match kind {
+            CommentKind::Block => {
                 // Whatever happens, we skip the first line.
                 let mut i = lines
                     .get(0)
@@ -73,8 +74,8 @@ pub fn beautify_doc_string(data: Symbol, kind: CommentKind) -> Symbol {
                     j -= 1;
                 }
                 &lines[i..j]
-        } else {
-            lines
+            }
+            CommentKind::Line => lines,
         };
 
         for line in lines {

compiler/rustc_const_eval/src/const_eval/machine.rs

@@ -622,10 +622,9 @@ impl<'mir, 'tcx> interpret::Machine<'mir, 'tcx> for CompileTimeInterpreter<'mir,
         let alloc = alloc.inner();
         if is_write {
             // Write access. These are never allowed, but we give a targeted error message.
-            if alloc.mutability == Mutability::Not {
-                Err(err_ub!(WriteToReadOnly(alloc_id)).into())
-            } else {
-                Err(ConstEvalErrKind::ModifiedGlobal.into())
+            match alloc.mutability {
+                Mutability::Not => Err(err_ub!(WriteToReadOnly(alloc_id)).into()),
+                Mutability::Mut => Err(ConstEvalErrKind::ModifiedGlobal.into()),
             }
         } else {
             // Read access. These are usually allowed, with some exceptions.

compiler/rustc_errors/src/emitter.rs

@@ -2113,9 +2113,11 @@ impl EmitterWriter {
                         }
                     }
                     for sugg in suggestions {
-                        if sugg.style == SuggestionStyle::CompletelyHidden {
+                        match sugg.style {
+                            SuggestionStyle::CompletelyHidden => {
                                 // do not display this suggestion, it is meant only for tools
-                        } else if sugg.style == SuggestionStyle::HideCodeAlways {
+                            }
+                            SuggestionStyle::HideCodeAlways => {
                                 if let Err(e) = self.emit_message_default(
                                     &MultiSpan::new(),
                                     &[(sugg.msg.to_owned(), Style::HeaderMsg)],
@@ -2128,7 +2130,11 @@ impl EmitterWriter {
                                 ) {
                                     panic!("failed to emit error: {}", e);
                                 }
-                        } else if let Err(e) = self.emit_suggestion_default(
+                            }
+                            SuggestionStyle::HideCodeInline
+                            | SuggestionStyle::ShowCode
+                            | SuggestionStyle::ShowAlways => {
+                                if let Err(e) = self.emit_suggestion_default(
                                     span,
                                     sugg,
                                     args,
@@ -2136,7 +2142,9 @@ impl EmitterWriter {
                                     max_line_num_len,
                                 ) {
                                     panic!("failed to emit error: {}", e);
-                        };
+                                }
+                            }
+                        }
                     }
                 }
             }

compiler/rustc_hir_analysis/src/astconv/generics.rs

@@ -385,10 +385,9 @@ pub fn check_generic_arg_count_for_call(
 ) -> GenericArgCountResult {
     let empty_args = hir::GenericArgs::none();
     let gen_args = seg.args.unwrap_or(&empty_args);
-    let gen_pos = if is_method_call == IsMethodCall::Yes {
-        GenericArgPosition::MethodCall
-    } else {
-        GenericArgPosition::Value
+    let gen_pos = match is_method_call {
+        IsMethodCall::Yes => GenericArgPosition::MethodCall,
+        IsMethodCall::No => GenericArgPosition::Value,
     };
     let has_self = generics.parent.is_none() && generics.has_self;
 

compiler/rustc_hir_analysis/src/check/check.rs

@@ -605,23 +605,29 @@ fn check_item_type(tcx: TyCtxt<'_>, id: hir::ItemId) {
             };
             check_abi(tcx, it.hir_id(), it.span, abi);
 
-            if abi == Abi::RustIntrinsic {
+            match abi {
+                Abi::RustIntrinsic => {
                     for item in items {
                         let item = tcx.hir().foreign_item(item.id);
                         intrinsic::check_intrinsic_type(tcx, item);
                     }
-            } else if abi == Abi::PlatformIntrinsic {
+                }
+
+                Abi::PlatformIntrinsic => {
                     for item in items {
                         let item = tcx.hir().foreign_item(item.id);
                         intrinsic::check_platform_intrinsic_type(tcx, item);
                     }
-            } else {
+                }
+
+                _ => {
                     for item in items {
                         let def_id = item.id.owner_id.def_id;
                         let generics = tcx.generics_of(def_id);
                         let own_counts = generics.own_counts();
                         if generics.params.len() - own_counts.lifetimes != 0 {
-                        let (kinds, kinds_pl, egs) = match (own_counts.types, own_counts.consts) {
+                            let (kinds, kinds_pl, egs) = match (own_counts.types, own_counts.consts)
+                            {
                                 (_, 0) => ("type", "types", Some("u32")),
                                 // We don't specify an example value, because we can't generate
                                 // a valid value for any type.
@@ -662,6 +668,7 @@ fn check_item_type(tcx: TyCtxt<'_>, id: hir::ItemId) {
                     }
                 }
             }
+        }
         DefKind::GlobalAsm => {
             let it = tcx.hir().item(id);
             let hir::ItemKind::GlobalAsm(asm) = it.kind else { span_bug!(it.span, "DefKind::GlobalAsm but got {:#?}", it) };

compiler/rustc_hir_typeck/src/method/probe.rs

@@ -1354,13 +1354,12 @@ impl<'a, 'tcx> ProbeContext<'a, 'tcx> {
             return Some(Err(MethodError::Ambiguity(sources)));
         }
 
-        applicable_candidates.pop().map(|(probe, status)| {
-            if status == ProbeResult::Match {
+        applicable_candidates.pop().map(|(probe, status)| match status {
+            ProbeResult::Match => {
                 Ok(probe
                     .to_unadjusted_pick(self_ty, unstable_candidates.cloned().unwrap_or_default()))
-            } else {
-                Err(MethodError::BadReturnType)
             }
+            ProbeResult::NoMatch | ProbeResult::BadReturnType => Err(MethodError::BadReturnType),
         })
     }
 }

compiler/rustc_lint/src/builtin.rs

@@ -580,14 +580,14 @@ impl<'tcx> LateLintPass<'tcx> for MissingDoc {
     }
 
     fn check_impl_item(&mut self, cx: &LateContext<'_>, impl_item: &hir::ImplItem<'_>) {
-        // If the method is an impl for a trait, don't doc.
         let context = method_context(cx, impl_item.owner_id.def_id);
-        if context == MethodLateContext::TraitImpl {
-            return;
-        }
         
+        match context {
+            // If the method is an impl for a trait, don't doc.
+            MethodLateContext::TraitImpl => return,
+            MethodLateContext::TraitAutoImpl => {}
             // If the method is an impl for an item with docs_hidden, don't doc.
-        if context == MethodLateContext::PlainImpl {
+            MethodLateContext::PlainImpl => {
                 let parent = cx.tcx.hir().get_parent_item(impl_item.hir_id());
                 let impl_ty = cx.tcx.type_of(parent);
                 let outerdef = match impl_ty.kind() {
@@ -603,6 +603,7 @@ impl<'tcx> LateLintPass<'tcx> for MissingDoc {
                     return;
                 }
             }
+        }
 
         let (article, desc) = cx.tcx.article_and_description(impl_item.owner_id.to_def_id());
         self.check_missing_docs_attrs(cx, impl_item.owner_id.def_id, article, desc);

compiler/rustc_metadata/src/dependency_format.rs

@@ -113,12 +113,10 @@ fn calculate_type(tcx: TyCtxt<'_>, ty: CrateType) -> DependencyList {
         CrateType::Staticlib => Linkage::Static,
     };
 
-    if preferred_linkage == Linkage::NotLinked {
+    match preferred_linkage {
         // If the crate is not linked, there are no link-time dependencies.
-        return Vec::new();
-    }
-
-    if preferred_linkage == Linkage::Static {
+        Linkage::NotLinked => return Vec::new(),
+        Linkage::Static => {
             // Attempt static linkage first. For dylibs and executables, we may be
             // able to retry below with dynamic linkage.
             if let Some(v) = attempt_static(tcx) {
@@ -145,6 +143,8 @@ fn calculate_type(tcx: TyCtxt<'_>, ty: CrateType) -> DependencyList {
                 return Vec::new();
             }
         }
+        Linkage::Dynamic | Linkage::IncludedFromDylib => {}
+    }
 
     let mut formats = FxHashMap::default();
 
@@ -283,12 +283,9 @@ fn attempt_static(tcx: TyCtxt<'_>) -> Option<DependencyList> {
     let mut ret = tcx
         .crates(())
         .iter()
-        .map(|&cnum| {
-            if tcx.dep_kind(cnum) == CrateDepKind::Explicit {
-                Linkage::Static
-            } else {
-                Linkage::NotLinked
-            }
+        .map(|&cnum| match tcx.dep_kind(cnum) {
+            CrateDepKind::Explicit => Linkage::Static,
+            CrateDepKind::MacrosOnly | CrateDepKind::Implicit => Linkage::NotLinked,
         })
         .collect::<Vec<_>>();
 

compiler/rustc_middle/src/mir/coverage.rs

@@ -135,7 +135,10 @@ impl Debug for CoverageKind {
                 "Expression({:?}) = {} {} {}",
                 id.index(),
                 lhs.index(),
-                if *op == Op::Add { "+" } else { "-" },
+                match op {
+                    Op::Add => "+",
+                    Op::Subtract => "-",
+                },
                 rhs.index(),
             ),
             Unreachable => write!(fmt, "Unreachable"),

compiler/rustc_mir_transform/src/coverage/debug.rs

@@ -323,7 +323,10 @@ impl DebugCounters {
                         String::new()
                     },
                     self.format_operand(lhs),
-                    if op == Op::Add { "+" } else { "-" },
+                    match op {
+                        Op::Add => "+",
+                        Op::Subtract => "-",
+                    },
                     self.format_operand(rhs),
                 );
             }

compiler/rustc_parse/src/parser/stmt.rs

@@ -93,11 +93,12 @@ impl<'a> Parser<'a> {
             // or `auto trait` items. We aim to parse an arbitrary path `a::b` but not something
             // that starts like a path (1 token), but it fact not a path.
             // Also, we avoid stealing syntax from `parse_item_`.
-            if force_collect == ForceCollect::Yes {
-                self.collect_tokens_no_attrs(|this| this.parse_stmt_path_start(lo, attrs))
-            } else {
-                self.parse_stmt_path_start(lo, attrs)
-            }?
+            match force_collect {
+                ForceCollect::Yes => {
+                    self.collect_tokens_no_attrs(|this| this.parse_stmt_path_start(lo, attrs))?
+                }
+                ForceCollect::No => self.parse_stmt_path_start(lo, attrs)?,
+            }
         } else if let Some(item) = self.parse_item_common(
             attrs.clone(),
             false,
@@ -113,13 +114,12 @@ impl<'a> Parser<'a> {
             self.mk_stmt(lo, StmtKind::Empty)
         } else if self.token != token::CloseDelim(Delimiter::Brace) {
             // Remainder are line-expr stmts.
-            let e = if force_collect == ForceCollect::Yes {
-                self.collect_tokens_no_attrs(|this| {
+            let e = match force_collect {
+                ForceCollect::Yes => self.collect_tokens_no_attrs(|this| {
                     this.parse_expr_res(Restrictions::STMT_EXPR, Some(attrs))
-                })
-            } else {
-                self.parse_expr_res(Restrictions::STMT_EXPR, Some(attrs))
-            }?;
+                })?,
+                ForceCollect::No => self.parse_expr_res(Restrictions::STMT_EXPR, Some(attrs))?,
+            };
             if matches!(e.kind, ExprKind::Assign(..)) && self.eat_keyword(kw::Else) {
                 let bl = self.parse_block()?;
                 // Destructuring assignment ... else.

compiler/rustc_parse/src/parser/ty.rs

@@ -323,14 +323,15 @@ impl<'a> Parser<'a> {
         } else if self.can_begin_bound() {
             self.parse_bare_trait_object(lo, allow_plus)?
         } else if self.eat(&token::DotDotDot) {
-            if allow_c_variadic == AllowCVariadic::Yes {
-                TyKind::CVarArgs
-            } else {
+            match allow_c_variadic {
+                AllowCVariadic::Yes => TyKind::CVarArgs,
+                AllowCVariadic::No => {
                     // FIXME(Centril): Should we just allow `...` syntactically
                     // anywhere in a type and use semantic restrictions instead?
                     self.error_illegal_c_varadic_ty(lo);
                     TyKind::Err
                 }
+            }
         } else {
             let msg = format!("expected type, found {}", super::token_descr(&self.token));
             let mut err = self.struct_span_err(self.token.span, &msg);
@@ -343,10 +344,9 @@ impl<'a> Parser<'a> {
         let mut ty = self.mk_ty(span, kind);
 
         // Try to recover from use of `+` with incorrect priority.
-        if allow_plus == AllowPlus::Yes {
-            self.maybe_recover_from_bad_type_plus(&ty)?;
-        } else {
-            self.maybe_report_ambiguous_plus(impl_dyn_multi, &ty);
+        match allow_plus {
+            AllowPlus::Yes => self.maybe_recover_from_bad_type_plus(&ty)?,
+            AllowPlus::No => self.maybe_report_ambiguous_plus(impl_dyn_multi, &ty),
         }
         if RecoverQuestionMark::Yes == recover_question_mark {
             ty = self.maybe_recover_from_question_mark(ty);

compiler/rustc_passes/src/check_attr.rs

@@ -864,13 +864,17 @@ impl CheckAttrVisitor<'_> {
         target: Target,
         specified_inline: &mut Option<(bool, Span)>,
     ) -> bool {
-        if target == Target::Use || target == Target::ExternCrate {
+        match target {
+            Target::Use | Target::ExternCrate => {
                 let do_inline = meta.name_or_empty() == sym::inline;
                 if let Some((prev_inline, prev_span)) = *specified_inline {
                     if do_inline != prev_inline {
                         let mut spans = MultiSpan::from_spans(vec![prev_span, meta.span()]);
                         spans.push_span_label(prev_span, fluent::passes_doc_inline_conflict_first);
-                    spans.push_span_label(meta.span(), fluent::passes_doc_inline_conflict_second);
+                        spans.push_span_label(
+                            meta.span(),
+                            fluent::passes_doc_inline_conflict_second,
+                        );
                         self.tcx.sess.emit_err(errors::DocKeywordConflict { spans });
                         return false;
                     }
@@ -879,7 +883,8 @@ impl CheckAttrVisitor<'_> {
                     *specified_inline = Some((do_inline, meta.span()));
                     true
                 }
-        } else {
+            }
+            _ => {
                 self.tcx.emit_spanned_lint(
                     INVALID_DOC_ATTRIBUTES,
                     hir_id,
@@ -893,6 +898,7 @@ impl CheckAttrVisitor<'_> {
                 false
             }
         }
+    }
 
     /// Checks that an attribute is *not* used at the crate level. Returns `true` if valid.
     fn check_attr_not_crate_level(
@@ -1137,7 +1143,7 @@ impl CheckAttrVisitor<'_> {
                                     errors::DocTestUnknownInclude {
                                         path,
                                         value: value.to_string(),
-                                        inner: if attr.style == AttrStyle::Inner { "!" } else { "" },
+                                        inner: match attr.style { AttrStyle::Inner=>  "!" , AttrStyle::Outer => "" },
                                         sugg: (attr.meta().unwrap().span, applicability),
                                     }
                                 );

compiler/rustc_resolve/src/build_reduced_graph.rs

@@ -298,9 +298,9 @@ impl<'a, 'b> BuildReducedGraphVisitor<'a, 'b> {
                             self.r.record_partial_res(id, PartialRes::new(res));
                         }
                         if module.is_normal() {
-                            if res == Res::Err {
-                                Ok(ty::Visibility::Public)
-                            } else {
+                            match res {
+                                Res::Err => Ok(ty::Visibility::Public),
+                                _ => {
                                     let vis = ty::Visibility::Restricted(res.def_id());
                                     if self.r.is_accessible_from(vis, parent_scope.module) {
                                         Ok(vis.expect_local())
@@ -308,6 +308,7 @@ impl<'a, 'b> BuildReducedGraphVisitor<'a, 'b> {
                                         Err(VisResolutionError::AncestorOnly(path.span))
                                     }
                                 }
+                            }
                         } else {
                             expected_found_error(res)
                         }

compiler/rustc_resolve/src/diagnostics.rs

@@ -1552,12 +1552,12 @@ impl<'a> Resolver<'a> {
             if b.is_extern_crate() && ident.span.rust_2018() {
                 help_msgs.push(format!("use `::{ident}` to refer to this {thing} unambiguously"))
             }
-            if misc == AmbiguityErrorMisc::SuggestCrate {
-                help_msgs
-                    .push(format!("use `crate::{ident}` to refer to this {thing} unambiguously"))
-            } else if misc == AmbiguityErrorMisc::SuggestSelf {
-                help_msgs
-                    .push(format!("use `self::{ident}` to refer to this {thing} unambiguously"))
+            match misc {
+                AmbiguityErrorMisc::SuggestCrate => help_msgs
+                    .push(format!("use `crate::{ident}` to refer to this {thing} unambiguously")),
+                AmbiguityErrorMisc::SuggestSelf => help_msgs
+                    .push(format!("use `self::{ident}` to refer to this {thing} unambiguously")),
+                AmbiguityErrorMisc::FromPrelude | AmbiguityErrorMisc::None => {}
             }
 
             err.span_note(b.span, &note_msg);

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

@@ -1230,14 +1230,16 @@ impl<'tcx> TypeErrCtxtExt<'tcx> for TypeErrCtxt<'_, 'tcx> {
                     }
 
                     ty::PredicateKind::WellFormed(ty) => {
-                        if self.tcx.sess.opts.unstable_opts.trait_solver == TraitSolver::Classic {
+                        match self.tcx.sess.opts.unstable_opts.trait_solver {
+                            TraitSolver::Classic => {
                                 // WF predicates cannot themselves make
                                 // errors. They can only block due to
                                 // ambiguity; otherwise, they always
                                 // degenerate into other obligations
                                 // (which may fail).
                                 span_bug!(span, "WF predicate not satisfied for {:?}", ty);
-                        } else {
+                            }
+                            TraitSolver::Chalk | TraitSolver::Next => {
                                 // FIXME: we'll need a better message which takes into account
                                 // which bounds actually failed to hold.
                                 self.tcx.sess.struct_span_err(
@@ -1246,6 +1248,7 @@ impl<'tcx> TypeErrCtxtExt<'tcx> for TypeErrCtxt<'_, 'tcx> {
                                 )
                             }
                         }
+                    }
 
                     ty::PredicateKind::ConstEvaluatable(..) => {
                         // Errors for `ConstEvaluatable` predicates show up as