refactor(isolated_declarations, linter, minifier, prettier, semantic,…

… transformer): remove unnecessary `ref` / `ref mut` syntax (#8643)

While working on #8641, I found a lot of places where we unnecessarily use `ref` / `ref mut` in match arms.

In many cases, we're creating double-references (turning a `&T` into a `&&T`). The compiler should be smart enough to remove them for us, but there doesn't seem much point in explicitly creating double-references when we don't actually want them, and relying on compiler to optimize them out again.

crates/oxc_isolated_declarations/src/class.rs

@@ -368,7 +368,7 @@ impl<'a> IsolatedDeclarations<'a> {
         for element in &decl.body.body {
             match element {
                 ClassElement::StaticBlock(_) => {}
-                ClassElement::MethodDefinition(ref method) => {
+                ClassElement::MethodDefinition(method) => {
                     if self.has_internal_annotation(method.span) {
                         continue;
                     }

crates/oxc_isolated_declarations/src/lib.rs

@@ -195,7 +195,7 @@ impl<'a> IsolatedDeclarations<'a> {
         // 2. Transform export declarations
         // 3. Collect all bindings / reference from module declarations
         // 4. Collect transformed indexes
-        for stmt in &stmts {
+        for &stmt in &stmts {
             match stmt {
                 match_declaration!(Statement) => {
                     if let Statement::TSModuleDeclaration(decl) = stmt {
@@ -433,8 +433,8 @@ impl<'a> IsolatedDeclarations<'a> {
         let mut last_function_name: Option<Atom<'a>> = None;
         let mut is_export_default_function_overloads = false;
 
-        stmts.retain(move |stmt| match stmt {
-            Statement::FunctionDeclaration(ref func) => {
+        stmts.retain(move |&stmt| match stmt {
+            Statement::FunctionDeclaration(func) => {
                 let name = func
                     .id
                     .as_ref()
@@ -454,8 +454,8 @@ impl<'a> IsolatedDeclarations<'a> {
                 }
                 true
             }
-            Statement::ExportNamedDeclaration(ref decl) => {
-                if let Some(Declaration::FunctionDeclaration(ref func)) = decl.declaration {
+            Statement::ExportNamedDeclaration(decl) => {
+                if let Some(Declaration::FunctionDeclaration(func)) = &decl.declaration {
                     let name = func
                         .id
                         .as_ref()
@@ -477,10 +477,8 @@ impl<'a> IsolatedDeclarations<'a> {
                     true
                 }
             }
-            Statement::ExportDefaultDeclaration(ref decl) => {
-                if let ExportDefaultDeclarationKind::FunctionDeclaration(ref func) =
-                    decl.declaration
-                {
+            Statement::ExportDefaultDeclaration(decl) => {
+                if let ExportDefaultDeclarationKind::FunctionDeclaration(func) = &decl.declaration {
                     if is_export_default_function_overloads && func.body.is_some() {
                         is_export_default_function_overloads = false;
                         return false;

crates/oxc_language_server/src/linter/isolated_lint_handler.rs

@@ -51,7 +51,7 @@ impl IsolatedLintHandler {
             // a diagnostics connected from related_info to original diagnostic
             let mut inverted_diagnostics = vec![];
             for d in &diagnostics {
-                let Some(ref related_info) = d.diagnostic.related_information else {
+                let Some(related_info) = &d.diagnostic.related_information else {
                     continue;
                 };
                 let related_information = Some(vec![DiagnosticRelatedInformation {

crates/oxc_linter/src/fixer/fix.rs

@@ -491,7 +491,7 @@ impl<'a> CompositeFix<'a> {
         let mut output = String::new();
 
         for fix in fixes {
-            let Fix { ref content, span } = fix;
+            let Fix { content, span } = fix;
             // negative range or overlapping ranges is invalid
             if span.start > span.end {
                 debug_assert!(false, "Negative range is invalid: {span:?}");
@@ -513,7 +513,7 @@ impl<'a> CompositeFix<'a> {
 
             output.reserve(before.len() + content.len());
             output.push_str(before);
-            output.push_str(content);
+            output.push_str(&content);
             last_pos = span.end;
         }
 

crates/oxc_linter/src/rules/eslint/getter_return.rs

@@ -227,7 +227,7 @@ impl GetterReturn {
                 // If the signature of function supports the return of the `undefined` value,
                 // you do not need to check this rule
                 if let AstKind::Function(func) = node.kind() {
-                    if let Some(ref ret) = func.return_type {
+                    if let Some(ret) = &func.return_type {
                         if ret.type_annotation.is_maybe_undefined() {
                             break 'returns true;
                         }

crates/oxc_linter/src/rules/eslint/no_regex_spaces.rs

@@ -158,7 +158,7 @@ impl<'a> Visit<'a> for ConsecutiveSpaceFinder {
         if ch.value != u32::from(b' ') {
             return;
         }
-        if let Some(ref mut space_span) = self.last_space_span {
+        if let Some(space_span) = &mut self.last_space_span {
             // If this is consecutive with the last space, extend it
             if space_span.end == ch.span.start {
                 space_span.end = ch.span.end;

crates/oxc_linter/src/rules/eslint/no_unused_vars/diagnostic.rs

@@ -45,7 +45,7 @@ where
         IgnorePattern::Default => {
             name.strip_prefix('_').map_or(".".into(), |name| format!(" to '{name}'."))
         }
-        IgnorePattern::Some(ref r) => {
+        IgnorePattern::Some(r) => {
             format!(" to match the pattern /{r}/.")
         }
     };

crates/oxc_linter/src/rules/eslint/no_unused_vars/options.rs

@@ -267,7 +267,7 @@ impl<R> IgnorePattern<R> {
         match self {
             Self::Default => IgnorePattern::Default,
             Self::None => IgnorePattern::None,
-            Self::Some(ref r) => IgnorePattern::Some(r),
+            Self::Some(r) => IgnorePattern::Some(r),
         }
     }
 }

crates/oxc_linter/src/rules/eslint/sort_imports.rs

@@ -266,7 +266,7 @@ impl SortImports {
         let specifiers: Vec<_> = specifiers
             .iter()
             .filter_map(|specifier| {
-                if let ImportDeclarationSpecifier::ImportSpecifier(ref specifier) = specifier {
+                if let ImportDeclarationSpecifier::ImportSpecifier(specifier) = specifier {
                     Some(specifier)
                 } else {
                     None

crates/oxc_linter/src/rules/import/first.rs

@@ -121,8 +121,8 @@ impl Rule for First {
 
         for statement in &program.body {
             match statement {
-                Statement::TSImportEqualsDeclaration(decl) => match decl.module_reference {
-                    TSModuleReference::ExternalModuleReference(ref mod_ref) => {
+                Statement::TSImportEqualsDeclaration(decl) => match &decl.module_reference {
+                    TSModuleReference::ExternalModuleReference(mod_ref) => {
                         if matches!(self.absolute_first, AbsoluteFirst::AbsoluteFirst) {
                             if is_relative_path(mod_ref.expression.value.as_str()) {
                                 any_relative = true;

crates/oxc_linter/src/rules/import/no_amd.rs

@@ -56,7 +56,7 @@ impl Rule for NoAmd {
             return;
         }
         if let AstKind::CallExpression(call_expr) = node.kind() {
-            if let Expression::Identifier(ref identifier) = &call_expr.callee {
+            if let Expression::Identifier(identifier) = &call_expr.callee {
                 if identifier.name != "define" && identifier.name != "require" {
                     return;
                 }

crates/oxc_linter/src/rules/jest/valid_describe_callback.rs

@@ -131,7 +131,7 @@ fn run<'a>(possible_jest_node: &PossibleJestNode<'a, '_>, ctx: &LintContext<'a>)
                 diagnostic(ctx, fn_expr.span, Message::UnexpectedDescribeArgument);
             }
 
-            let Some(ref body) = fn_expr.body else {
+            let Some(body) = &fn_expr.body else {
                 return;
             };
             if let Some(span) = find_first_return_stmt_span(body) {

crates/oxc_linter/src/rules/jsdoc/require_returns.rs

@@ -149,7 +149,7 @@ impl Rule for RequireReturns {
                         match parent_node.kind() {
                             AstKind::Function(_) | AstKind::ArrowFunctionExpression(_) => {
                                 // Ignore `return;`
-                                let Some(ref argument) = return_stmt.argument else {
+                                let Some(argument) = &return_stmt.argument else {
                                     continue 'visit_node;
                                 };
 

crates/oxc_linter/src/rules/nextjs/no_typos.rs

@@ -69,7 +69,7 @@ impl Rule for NoTypos {
         if let AstKind::ModuleDeclaration(ModuleDeclaration::ExportNamedDeclaration(en_decl)) =
             node.kind()
         {
-            if let Some(ref decl) = en_decl.declaration {
+            if let Some(decl) = &en_decl.declaration {
                 match decl {
                     Declaration::VariableDeclaration(decl) => {
                         for decl in &decl.declarations {

crates/oxc_linter/src/rules/oxc/no_accumulating_spread.rs

@@ -129,7 +129,7 @@ impl Rule for NoAccumulatingSpread {
         let AstKind::SpreadElement(spread) = node.kind() else {
             return;
         };
-        let Expression::Identifier(ref ident) = spread.argument else {
+        let Expression::Identifier(ident) = &spread.argument else {
             return;
         };
 

crates/oxc_linter/src/rules/react/jsx_no_undef.rs

@@ -41,7 +41,7 @@ fn get_resolvable_ident<'a>(node: &'a JSXElementName<'a>) -> Option<&'a Identifi
         JSXElementName::Identifier(_)
         | JSXElementName::NamespacedName(_)
         | JSXElementName::ThisExpression(_) => None,
-        JSXElementName::IdentifierReference(ref ident) => Some(ident),
+        JSXElementName::IdentifierReference(ident) => Some(ident),
         JSXElementName::MemberExpression(expr) => get_member_ident(expr),
     }
 }

crates/oxc_linter/src/rules/typescript/ban_ts_comment.rs

@@ -202,7 +202,7 @@ impl Rule for BanTsComment {
                             ));
                         }
 
-                        if let DirectiveConfig::DescriptionFormat(Some(ref re)) = config {
+                        if let DirectiveConfig::DescriptionFormat(Some(re)) = config {
                             if !re.is_match(description) {
                                 ctx.diagnostic(comment_description_not_match_pattern(
                                     directive,

crates/oxc_linter/src/rules/typescript/no_require_imports.rs

@@ -193,8 +193,8 @@ impl Rule for NoRequireImports {
 
                 ctx.diagnostic(no_require_imports_diagnostic(call_expr.span));
             }
-            AstKind::TSImportEqualsDeclaration(decl) => match decl.module_reference {
-                TSModuleReference::ExternalModuleReference(ref mod_ref) => {
+            AstKind::TSImportEqualsDeclaration(decl) => match &decl.module_reference {
+                TSModuleReference::ExternalModuleReference(mod_ref) => {
                     if self.allow_as_import {
                         return;
                     }

crates/oxc_linter/src/rules/typescript/triple_slash_reference.rs

@@ -134,8 +134,8 @@ impl Rule for TripleSlashReference {
         if !refs_for_import.is_empty() {
             for stmt in &program.body {
                 match stmt {
-                    Statement::TSImportEqualsDeclaration(decl) => match decl.module_reference {
-                        TSModuleReference::ExternalModuleReference(ref mod_ref) => {
+                    Statement::TSImportEqualsDeclaration(decl) => match &decl.module_reference {
+                        TSModuleReference::ExternalModuleReference(mod_ref) => {
                             if let Some(v) = refs_for_import.get(mod_ref.expression.value.as_str())
                             {
                                 ctx.diagnostic(triple_slash_reference_diagnostic(

crates/oxc_linter/src/rules/unicorn/no_thenable.rs

@@ -84,7 +84,7 @@ impl Rule for NoThenable {
             }
             AstKind::ModuleDeclaration(ModuleDeclaration::ExportNamedDeclaration(decl)) => {
                 // check declaration
-                if let Some(ref decl) = decl.declaration {
+                if let Some(decl) = &decl.declaration {
                     match decl {
                         Declaration::VariableDeclaration(decl) => {
                             for decl in &decl.declarations {
@@ -242,8 +242,8 @@ fn check_expression(expr: &Expression, ctx: &LintContext<'_>) -> Option<oxc_span
                 let decl = ctx.semantic().nodes().get_node(symbols.get_declaration(symbol_id));
                 let var_decl = decl.kind().as_variable_declarator()?;
 
-                match var_decl.init {
-                    Some(Expression::StringLiteral(ref lit)) => {
+                match &var_decl.init {
+                    Some(Expression::StringLiteral(lit)) => {
                         if lit.value == "then" {
                             Some(lit.span)
                         } else {

crates/oxc_linter/src/rules/unicorn/prefer_array_flat.rs

@@ -145,7 +145,7 @@ fn check_array_reduce_case<'a>(call_expr: &CallExpression<'a>, ctx: &LintContext
             &first_argument.params.items[1].pattern.kind,
         ) {
             (
-                BindingPatternKind::BindingIdentifier(ref first_param),
+                BindingPatternKind::BindingIdentifier(first_param),
                 BindingPatternKind::BindingIdentifier(second_param),
             ) => Some((&first_param.name, &second_param.name)),
 

crates/oxc_minifier/src/peephole/minimize_conditions.rs

@@ -339,7 +339,7 @@ impl<'a> PeepholeOptimizations {
             if sequence_expr.expressions.len() > 1 {
                 let span = expr.span();
                 let mut sequence = ctx.ast.move_expression(&mut expr.test);
-                let Expression::SequenceExpression(ref mut sequence_expr) = &mut sequence else {
+                let Expression::SequenceExpression(sequence_expr) = &mut sequence else {
                     unreachable!()
                 };
                 let test = sequence_expr.expressions.pop().unwrap();
@@ -587,15 +587,13 @@ impl<'a> PeepholeOptimizations {
                 {
                     let callee = ctx.ast.move_expression(&mut consequent.callee);
                     let consequent_first_arg = {
-                        let Argument::SpreadElement(ref mut el) = &mut consequent.arguments[0]
-                        else {
+                        let Argument::SpreadElement(el) = &mut consequent.arguments[0] else {
                             unreachable!()
                         };
                         ctx.ast.move_expression(&mut el.argument)
                     };
                     let alternate_first_arg = {
-                        let Argument::SpreadElement(ref mut el) = &mut alternate.arguments[0]
-                        else {
+                        let Argument::SpreadElement(el) = &mut alternate.arguments[0] else {
                             unreachable!()
                         };
                         ctx.ast.move_expression(&mut el.argument)

crates/oxc_prettier/src/format/js.rs

@@ -1558,11 +1558,11 @@ impl<'a> Format<'a> for PrivateIdentifier<'a> {
 impl<'a> Format<'a> for BindingPattern<'a> {
     fn format(&self, p: &mut Prettier<'a>) -> Doc<'a> {
         let mut parts = Vec::new_in(p.allocator);
-        parts.push(match self.kind {
-            BindingPatternKind::BindingIdentifier(ref ident) => ident.format(p),
-            BindingPatternKind::ObjectPattern(ref pattern) => pattern.format(p),
-            BindingPatternKind::ArrayPattern(ref pattern) => pattern.format(p),
-            BindingPatternKind::AssignmentPattern(ref pattern) => pattern.format(p),
+        parts.push(match &self.kind {
+            BindingPatternKind::BindingIdentifier(ident) => ident.format(p),
+            BindingPatternKind::ObjectPattern(pattern) => pattern.format(p),
+            BindingPatternKind::ArrayPattern(pattern) => pattern.format(p),
+            BindingPatternKind::AssignmentPattern(pattern) => pattern.format(p),
         });
 
         if self.optional {

crates/oxc_semantic/src/builder.rs

@@ -39,7 +39,7 @@ use crate::{
 
 macro_rules! control_flow {
     ($self:ident, |$cfg:tt| $body:expr) => {
-        if let Some(ref mut $cfg) = $self.cfg {
+        if let Some($cfg) = &mut $self.cfg {
             $body
         } else {
             Default::default()

crates/oxc_semantic/src/dot.rs

@@ -124,7 +124,7 @@ impl DebugDot for BasicBlock {
 
 impl DebugDot for Instruction {
     fn debug_dot(&self, ctx: DebugDotContext) -> String {
-        match self.kind {
+        match &self.kind {
             InstructionKind::Statement => {
                 self.node_id.map_or("None".to_string(), |id| ctx.debug_ast_kind(id))
             }
@@ -136,7 +136,7 @@ impl DebugDot for Instruction {
                     ctx.try_eval_literal(id).unwrap_or_else(|| ctx.debug_ast_kind(id))
                 )
             }),
-            InstructionKind::Iteration(ref kind) => {
+            InstructionKind::Iteration(kind) => {
                 format!(
                     "Iteration({} {} {})",
                     self.node_id.map_or("None".to_string(), |id| ctx.debug_ast_kind(id)),

crates/oxc_transformer/src/jsx/refresh.rs

@@ -313,7 +313,7 @@ impl<'a> Traverse<'a> for ReactRefresh<'a, '_> {
 
         let hook_name = match &call_expr.callee {
             Expression::Identifier(ident) => ident.name,
-            Expression::StaticMemberExpression(ref member) => member.property.name,
+            Expression::StaticMemberExpression(member) => member.property.name,
             _ => return,
         };
 
@@ -434,7 +434,7 @@ impl<'a> ReactRefresh<'a, '_> {
         ctx: &mut TraverseCtx<'a>,
     ) -> bool {
         match expr {
-            Expression::Identifier(ref ident) => {
+            Expression::Identifier(ident) => {
                 // For case like:
                 // export const Something = hoc(Foo)
                 // we don't want to wrap Foo inside the call.
@@ -451,7 +451,7 @@ impl<'a> ReactRefresh<'a, '_> {
                     return false;
                 }
             }
-            Expression::CallExpression(ref mut call_expr) => {
+            Expression::CallExpression(call_expr) => {
                 let allowed_callee = matches!(
                     call_expr.callee,
                     Expression::Identifier(_)
@@ -660,7 +660,7 @@ impl<'a> ReactRefresh<'a, '_> {
                     None
                 }
             }
-            Statement::ExportDefaultDeclaration(ref mut stmt_decl) => {
+            Statement::ExportDefaultDeclaration(stmt_decl) => {
                 match &mut stmt_decl.declaration {
                     declaration @ match_expression!(ExportDefaultDeclarationKind) => {
                         let expression = declaration.to_expression_mut();

crates/oxc_transformer/src/options/browserslist_query.rs

@@ -33,14 +33,14 @@ impl BrowserslistQuery {
         };
 
         let result = match self {
-            BrowserslistQuery::Single(ref s) => {
+            BrowserslistQuery::Single(s) => {
                 if s.is_empty() {
                     browserslist::resolve(&["defaults"], &options)
                 } else {
                     browserslist::resolve(&[s], &options)
                 }
             }
-            BrowserslistQuery::Multiple(ref s) => browserslist::resolve(s, &options),
+            BrowserslistQuery::Multiple(s) => browserslist::resolve(s, &options),
         };
 
         let result = match result {