feat(allocator): Add maybe types

bindings/binding_core_node/src/bundle.rs

@@ -63,7 +63,7 @@ impl Task for BundleTask {
                 .map(JsWord::from)
                 .collect::<Vec<_>>()
         } else {
-            vec![]
+            Vec::new()
         };
 
         // Defaults to es3

crates/ast_node/src/ast_node_macro.rs

@@ -16,7 +16,7 @@ impl Parse for Args {
 }
 
 pub fn expand_struct(args: Args, i: DeriveInput) -> Vec<ItemImpl> {
-    let mut items = vec![];
+    let mut items = Vec::new();
     let generics = i.generics.clone();
     // let item_ident = Ident::new("Item", i.ident.span());
 
@@ -128,7 +128,7 @@ pub fn expand_struct(args: Args, i: DeriveInput) -> Vec<ItemImpl> {
     //     let item = DeriveInput {
     //         vis: Visibility::Inherited,
     //         ident: item_ident,
-    //         attrs: vec![],
+    //         attrs: Vec::new(),
     //         data: item_data,
     //         ..cloned
     //     };

crates/ast_node/src/enum_deserialize.rs

@@ -113,8 +113,8 @@ pub fn expand(
             .collect::<Vec<Arm>>();
 
         let tag_expr: Expr = {
-            let mut visit_str_arms = vec![];
-            let mut visit_bytes_arms = vec![];
+            let mut visit_str_arms = Vec::new();
+            let mut visit_bytes_arms = Vec::new();
 
             for variant in &data.variants {
                 let tags = variant

crates/dbg-swc/src/util/mod.rs

@@ -49,7 +49,7 @@ pub fn parse_js(fm: Arc<SourceFile>) -> Result<ModuleRecord> {
     let unresolved_mark = Mark::new();
     let top_level_mark = Mark::new();
 
-    let mut errors = vec![];
+    let mut errors = Vec::new();
     let comments = SingleThreadedComments::default();
     let res = parse_file_as_module(
         &fm,
@@ -80,7 +80,7 @@ pub fn parse_js(fm: Arc<SourceFile>) -> Result<ModuleRecord> {
 }
 
 pub fn print_js(cm: Arc<SourceMap>, m: &Module, minify: bool) -> Result<String> {
-    let mut buf = vec![];
+    let mut buf = Vec::new();
 
     {
         let mut wr = Box::new(JsWriter::new(cm.clone(), "\n", &mut buf, None)) as Box<dyn WriteJs>;
@@ -112,7 +112,7 @@ pub struct ModuleRecord {
 pub fn all_js_files(path: &Path) -> Result<Vec<PathBuf>> {
     wrap_task(|| {
         if path.is_dir() {
-            let mut files = vec![];
+            let mut files = Vec::new();
             for entry in path.read_dir().context("failed to read dir")? {
                 let entry = entry.context("read_dir returned an error")?;
                 let path = entry.path();
@@ -122,7 +122,7 @@ pub fn all_js_files(path: &Path) -> Result<Vec<PathBuf>> {
         } else if path.extension() == Some("js".as_ref()) {
             Ok(vec![path.to_path_buf()])
         } else {
-            Ok(vec![])
+            Ok(Vec::new())
         }
     })
     .with_context(|| format!("failed to get list of `.js` files in {}", path.display()))

crates/from_variant/src/lib.rs

@@ -32,7 +32,7 @@ fn derive(
         _ => panic!("#[derive(FromVariant)] only works for an enum."),
     };
 
-    let mut from_impls: Vec<ItemImpl> = vec![];
+    let mut from_impls: Vec<ItemImpl> = Vec::new();
 
     for v in variants {
         let variant_name = v.ident;

crates/jsdoc/src/lib.rs

@@ -14,7 +14,7 @@ mod input;
 pub fn parse(i: Input) -> IResult<Input, JsDoc> {
     let i = skip(i);
 
-    let mut tags = vec![];
+    let mut tags = Vec::new();
     let lo = i.span().lo;
     let (description, mut i) = take_while(|c| c != '@')(i)?;
     let description = trim(description).into();
@@ -546,7 +546,7 @@ fn parse_one_of<'i>(i: Input<'i>, list: &[&str]) -> IResult<Input<'i>, Text> {
 
 fn parse_name_path(mut i: Input) -> IResult<Input, NamePath> {
     let lo = i.span().lo;
-    let mut components = vec![];
+    let mut components = Vec::new();
 
     loop {
         let (input, component) = parse_word(i)?;

crates/jsdoc/tests/fixture.rs

@@ -15,7 +15,7 @@ fn fixture(path: PathBuf) {
 
         let fm = cm.load_file(&path).expect("failed to load fixture file");
 
-        let mut errors = vec![];
+        let mut errors = Vec::new();
 
         if let Err(err) = parse_file_as_module(
             &fm,
@@ -35,7 +35,7 @@ fn fixture(path: PathBuf) {
         if handler.has_errors() {
             return Err(());
         }
-        let mut res = vec![];
+        let mut res = Vec::new();
         let mut comments: Vec<_> = comments.leading.into_iter().collect();
         comments.sort_by_key(|v| v.0);
 

crates/swc/src/config/mod.rs

@@ -1548,7 +1548,7 @@ impl GlobalPassOption {
         fn expr(cm: &SourceMap, handler: &Handler, src: String) -> Box<Expr> {
             let fm = cm.new_source_file(FileName::Anon.into(), src);
 
-            let mut errors = vec![];
+            let mut errors = Vec::new();
             let expr = parse_file_as_expr(
                 &fm,
                 Syntax::Es(Default::default()),

crates/swc/tests/tsc.rs

@@ -113,7 +113,7 @@ fn matrix(input: &Path) -> Vec<TestUnitData> {
 
     let mut sub_filename = filename;
 
-    let mut files = vec![];
+    let mut files = Vec::new();
 
     let mut buffer = String::default();
     for line in fm.src.lines() {
@@ -344,7 +344,7 @@ fn matrix(input: &Path) -> Vec<TestUnitData> {
     "#,
     );
 
-    let mut test_unit_data_list = vec![];
+    let mut test_unit_data_list = Vec::new();
 
     let is_jsx = input
         .extension()
@@ -357,7 +357,7 @@ fn matrix(input: &Path) -> Vec<TestUnitData> {
     for minify in [None, Some(default_minify)] {
         for target in targets.clone() {
             for module in modules.clone() {
-                let mut vary_name = vec![];
+                let mut vary_name = Vec::new();
 
                 if modules.len() > 1 {
                     vary_name.push(format!("module={}", &module));

crates/swc_allocator/src/lib.rs

@@ -42,6 +42,15 @@ pub mod boxed;
 #[cfg(feature = "nightly")]
 pub mod vec;
 
+/// Box<T> and Vec<T> depeding on the feature.
+pub mod maybe {
+    #[cfg(not(feature = "nightly"))]
+    pub use std::{boxed, vec};
+
+    #[cfg(feature = "nightly")]
+    pub use crate::{boxed, vec};
+}
+
 /// Fast allocator, effectively working as a cache.
 ///
 /// This type implements [Default] and [Copy]. This type is intended to stored

crates/swc_allocator/src/vec/mod.rs

@@ -381,3 +381,9 @@ impl io::Write for Vec<u8> {
         self
     }
 }
+
+impl<T> AsRef<[T]> for Vec<T> {
+    fn as_ref(&self) -> &[T] {
+        self.0.as_ref()
+    }
+}

crates/swc_bundler/examples/bundle.rs

@@ -36,7 +36,7 @@ use swc_ecma_visit::VisitMutWith;
 fn print_bundles(cm: Lrc<SourceMap>, modules: Vec<Bundle>, minify: bool) {
     for bundled in modules {
         let code = {
-            let mut buf = vec![];
+            let mut buf = Vec::new();
 
             {
                 let wr = JsWriter::new(cm.clone(), "\n", &mut buf, None);
@@ -232,7 +232,7 @@ impl Load for Loader {
             Syntax::Es(Default::default()),
             EsVersion::Es2020,
             None,
-            &mut vec![],
+            &mut Vec::new(),
         )
         .unwrap_or_else(|err| {
             let handler =

crates/swc_bundler/examples/path.rs

@@ -14,7 +14,7 @@ fn main() {
     let globals = Globals::new();
     let cm = Lrc::new(SourceMap::new(FilePathMapping::empty()));
     // This example does not use core modules.
-    let external_modules = vec![];
+    let external_modules = Vec::new();
     let mut bundler = Bundler::new(
         &globals,
         cm.clone(),
@@ -74,7 +74,7 @@ impl Load for PathLoader {
             Syntax::Es(Default::default()),
             Default::default(),
             None,
-            &mut vec![],
+            &mut Vec::new(),
         )
         .expect("This should not happen");
 

crates/swc_bundler/src/bundler/chunk/cjs.rs

@@ -126,7 +126,7 @@ fn wrap_module(
                     pat: Pat::Ident(Ident::new("exports".into(), DUMMY_SP, local_ctxt).into()),
                 },
             ],
-            decorators: vec![],
+            decorators: Vec::new(),
             span: DUMMY_SP,
             body: Some(BlockStmt {
                 span: dep.span,
@@ -205,7 +205,7 @@ where
                         let load = CallExpr {
                             span: node.span,
                             callee: Ident::new("load".into(), i.span, i.ctxt).as_callee(),
-                            args: vec![],
+                            args: Vec::new(),
                             ..Default::default()
                         };
                         self.replaced = true;
@@ -253,7 +253,7 @@ where
                 *node = CallExpr {
                     span: DUMMY_SP,
                     callee: load_var.as_callee(),
-                    args: vec![],
+                    args: Vec::new(),
 
                     ..Default::default()
                 }
@@ -262,7 +262,7 @@ where
                 return;
             }
 
-            let mut props = vec![];
+            let mut props = Vec::new();
             // TODO
             for spec in i.specifiers.clone() {
                 match spec {
@@ -303,7 +303,7 @@ where
                                     CallExpr {
                                         span: DUMMY_SP,
                                         callee: load_var.as_callee(),
-                                        args: vec![],
+                                        args: Vec::new(),
 
                                         ..Default::default()
                                     }
@@ -335,7 +335,7 @@ where
                     init: Some(Box::new(Expr::Call(CallExpr {
                         span: DUMMY_SP,
                         callee: load_var.as_callee(),
-                        args: vec![],
+                        args: Vec::new(),
                         ..Default::default()
                     }))),
                     definite: false,

crates/swc_bundler/src/bundler/chunk/computed_key.rs

@@ -48,7 +48,7 @@ where
 
         let is_async = module.iter().any(|m| contains_top_level_await(m.1));
 
-        let mut additional_items = vec![];
+        let mut additional_items = Vec::new();
 
         module.iter().for_each(|(module_id, item)| {
             match item {

crates/swc_bundler/src/bundler/chunk/merge.rs

@@ -183,7 +183,7 @@ where
         {
             // Handle `export *` for non-wrapped modules.
 
-            let mut vars = vec![];
+            let mut vars = Vec::new();
             /// We recurse if `export *` is nested.
             fn add_var(
                 injected_ctxt: SyntaxContext,
@@ -568,7 +568,7 @@ where
             return;
         }
 
-        let mut extra = vec![];
+        let mut extra = Vec::new();
 
         module.map_any_items(|_, items| {
             let mut new = Vec::with_capacity(items.len() * 11 / 10);
@@ -977,7 +977,7 @@ where
                                 if !dep.is_es6 {
                                     dep.helpers.require.store(true, Ordering::SeqCst);
 
-                                    let mut vars = vec![];
+                                    let mut vars = Vec::new();
                                     let mod_var = private_ident!("_cjs_module_");
 
                                     vars.push(VarDeclarator {
@@ -1234,7 +1234,7 @@ where
     pub(super) fn replace_import_specifiers(&self, info: &TransformedModule, module: &mut Modules) {
         let injected_ctxt = self.injected_ctxt;
 
-        let mut vars = vec![];
+        let mut vars = Vec::new();
         module.map_any_items(|module_id, stmts| {
             let mut new = Vec::with_capacity(stmts.len() + 32);
 

crates/swc_bundler/src/bundler/finalize.rs

@@ -150,7 +150,7 @@ where
         let is_async = contains_top_level_await(&module);
 
         // Properties of returned object
-        let mut props = vec![];
+        let mut props = Vec::new();
 
         let mut body = BlockStmt {
             span: module.span,

crates/swc_bundler/src/bundler/helpers/mod.rs

@@ -20,7 +20,7 @@ fn parse(code: &'static str, name: &'static str) -> Vec<ModuleItem> {
         Default::default(),
         Default::default(),
         None,
-        &mut vec![],
+        &mut Vec::new(),
     )
     .map(|script| drop_span(script.body))
     .map_err(|_| {})
@@ -59,7 +59,7 @@ impl Helpers {
     }
 
     pub fn add_to(&self, to: &mut Vec<ModuleItem>) {
-        let mut buf = vec![];
+        let mut buf = Vec::new();
 
         if self.require.load(SeqCst) {
             build_swcpack_require(&mut buf);

crates/swc_bundler/src/bundler/import/mod.rs

@@ -239,7 +239,7 @@ where
 
                         let decl = ImportDecl {
                             span,
-                            specifiers: vec![],
+                            specifiers: Vec::new(),
                             src: Box::new(src.clone()),
                             type_only: false,
                             with: None,
@@ -544,7 +544,7 @@ where
         });
 
         if self.deglob_phase {
-            let mut wrapping_required = vec![];
+            let mut wrapping_required = Vec::new();
             for import in self.info.imports.iter_mut() {
                 let use_ns = self.info.forced_ns.contains(&import.src.value)
                     || self