refactor(es/compat): Use special span instead of passing `static_bloc…

…ks_mark` (#9725)

**Description:**

Let's make an assumption in the code: the use of dummy span as a private class field name is generated by us, it is there simply because it is necessary to maintain the order of side effect execution, its name is not referenced elsewhere, so we can safely remove its name.

This is a breaking change for Rust users.

.changeset/smart-cherries-sleep.md

@@ -0,0 +1,6 @@
+---
+swc_common: patch
+swc_ecma_compat_es2022: major
+---
+
+refactor(es/compat): Use dummy span instead of passing `static_blocks_mark`

crates/swc/src/builder.rs

@@ -215,7 +215,6 @@ impl<'a, 'b, P: Pass> PassBuilder<'a, 'b, P> {
                                 constant_super: assumptions.constant_super,
                                 set_public_fields: assumptions.set_public_class_fields,
                                 no_document_all: assumptions.no_document_all,
-                                static_blocks_mark: Mark::new(),
                                 pure_getter: assumptions.pure_getters,
                             },
                         },

crates/swc_common/src/syntax_pos.rs

@@ -85,11 +85,18 @@ pub const DUMMY_SP: Span = Span {
     hi: BytePos::DUMMY,
 };
 
+/// PURE span, will emit `/* #__PURE__ */` comment in codegen.
 pub const PURE_SP: Span = Span {
     lo: BytePos::PURE,
     hi: BytePos::PURE,
 };
 
+/// Used for some special cases. e.g. mark the generated AST.
+pub const PLACEHOLDER_SP: Span = Span {
+    lo: BytePos::PLACEHOLDER,
+    hi: BytePos::PLACEHOLDER,
+};
+
 pub struct Globals {
     hygiene_data: Mutex<hygiene::HygieneData>,
     #[allow(unused)]
@@ -408,6 +415,11 @@ impl Span {
         self.lo.is_pure()
     }
 
+    #[inline]
+    pub fn is_placeholder(self) -> bool {
+        self.lo.is_placeholder()
+    }
+
     /// Returns `true` if this is a dummy span with any hygienic context.
     #[inline]
     pub fn is_dummy_ignoring_cmt(self) -> bool {
@@ -1032,6 +1044,10 @@ impl BytePos {
     /// Dummy position. This is reserved for synthesized spans.
     pub const DUMMY: Self = BytePos(0);
     const MIN_RESERVED: Self = BytePos(DUMMY_RESERVE);
+    /// Placeholders, commonly used where names are required, but the names are
+    /// not referenced elsewhere.
+    pub const PLACEHOLDER: Self = BytePos(u32::MAX - 2);
+    /// Reserved for PURE comments. e.g. `/* #__PURE__ */`
     pub const PURE: Self = BytePos(u32::MAX - 1);
     /// Synthesized, but should be stored in a source map.
     pub const SYNTHESIZED: Self = BytePos(u32::MAX);
@@ -1050,6 +1066,10 @@ impl BytePos {
         self.0 == Self::PURE.0
     }
 
+    pub const fn is_placeholder(self) -> bool {
+        self.0 == Self::PLACEHOLDER.0
+    }
+
     /// Returns `true`` if this is explicitly synthesized or has relevant input
     /// source so can have a comment.
     pub const fn can_have_comment(self) -> bool {

crates/swc_ecma_compat_es2022/src/class_properties/mod.rs

@@ -49,27 +49,13 @@ pub fn class_properties(config: Config, unresolved_mark: Mark) -> impl Pass {
     })
 }
 
-#[derive(Debug, Clone, Copy)]
+#[derive(Debug, Default, Clone, Copy)]
 pub struct Config {
     pub private_as_properties: bool,
     pub set_public_fields: bool,
     pub constant_super: bool,
     pub no_document_all: bool,
     pub pure_getter: bool,
-    pub static_blocks_mark: Mark,
-}
-
-impl Default for Config {
-    fn default() -> Self {
-        Self {
-            private_as_properties: false,
-            set_public_fields: false,
-            constant_super: false,
-            no_document_all: false,
-            pure_getter: false,
-            static_blocks_mark: Mark::new(),
-        }
-    }
 }
 
 struct ClassProperties {
@@ -734,7 +720,7 @@ impl ClassProperties {
 
                     let value = prop.value.unwrap_or_else(|| Expr::undefined(prop_span));
 
-                    if prop.is_static && prop.ctxt.has_mark(self.c.static_blocks_mark) {
+                    if prop.is_static && prop.key.span.is_placeholder() {
                         let init = MemberInit::StaticBlock(value);
                         extra_inits.push(init);
                         continue;

crates/swc_ecma_compat_es2022/src/lib.rs

@@ -26,7 +26,7 @@ pub fn es2022(config: Config, unresolved_mark: Mark) -> impl Pass {
             unicode_regex: false,
             unicode_sets_regex: false,
         }),
-        static_blocks(config.class_properties.static_blocks_mark),
+        static_blocks(),
         class_properties(config.class_properties, unresolved_mark),
         private_in_object(),
     )

crates/swc_ecma_compat_es2022/src/static_blocks.rs

@@ -1,16 +1,14 @@
 use swc_atoms::JsWord;
-use swc_common::{collections::AHashSet, util::take::Take, Mark, SyntaxContext, DUMMY_SP};
+use swc_common::{collections::AHashSet, source_map::PLACEHOLDER_SP, util::take::Take};
 use swc_ecma_ast::*;
 use swc_ecma_utils::ExprFactory;
 use swc_ecma_visit::{noop_visit_mut_type, visit_mut_pass, VisitMut, VisitMutWith};
 use swc_trace_macro::swc_trace;
 
-struct ClassStaticBlock {
-    static_block_mark: Mark,
-}
+struct ClassStaticBlock;
 
-pub fn static_blocks(static_block_mark: Mark) -> impl Pass {
-    visit_mut_pass(ClassStaticBlock { static_block_mark })
+pub fn static_blocks() -> impl Pass {
+    visit_mut_pass(ClassStaticBlock)
 }
 
 #[swc_trace]
@@ -31,17 +29,11 @@ impl ClassStaticBlock {
             static_block.body.stmts = stmts;
 
             let expr = CallExpr {
-                span: DUMMY_SP,
                 callee: ArrowExpr {
-                    span: DUMMY_SP,
-                    params: Vec::new(),
-                    is_async: false,
-                    is_generator: false,
                     body: Box::new(BlockStmtOrExpr::BlockStmt(static_block.body)),
                     ..Default::default()
                 }
                 .as_callee(),
-                args: Vec::new(),
                 ..Default::default()
             }
             .into();
@@ -52,19 +44,12 @@ impl ClassStaticBlock {
         PrivateProp {
             span,
             is_static: true,
-            is_optional: false,
-            is_override: false,
-            readonly: false,
-            type_ann: None,
-            decorators: Vec::new(),
-            accessibility: None,
             key: PrivateName {
-                span: DUMMY_SP,
+                span: PLACEHOLDER_SP,
                 name: private_id,
             },
             value,
-            definite: false,
-            ctxt: SyntaxContext::empty().apply_mark(self.static_block_mark),
+            ..Default::default()
         }
     }
 }

crates/swc_ecma_preset_env/src/lib.rs

@@ -133,12 +133,8 @@ where
     // ES2022
     // static block needs to be placed before class property
     // because it transforms into private static property
-    let static_blocks_mark = Mark::new();
-    let pass = add!(
-        pass,
-        ClassStaticBlock,
-        es2022::static_blocks(static_blocks_mark)
-    );
+
+    let pass = add!(pass, ClassStaticBlock, es2022::static_blocks());
     let pass = add!(
         pass,
         ClassProperties,
@@ -148,7 +144,6 @@ where
                 set_public_fields: loose || assumptions.set_public_class_fields,
                 constant_super: loose || assumptions.constant_super,
                 no_document_all: loose || assumptions.no_document_all,
-                static_blocks_mark,
                 pure_getter: loose || assumptions.pure_getters,
             },
             unresolved_mark

crates/swc_ecma_transforms_compat/tests/es2015_new_target.rs

@@ -46,7 +46,6 @@ fn get_passes(_: &Tester, plugins: &[PluginConfig]) -> Box<dyn Pass> {
                             set_public_fields: loose,
                             private_as_properties: loose,
                             no_document_all: loose,
-                            static_blocks_mark: Mark::new(),
                             pure_getter: loose,
                         },
                         unresolved_mark,

crates/swc_ecma_transforms_compat/tests/es2022_private_in_object.rs

@@ -64,7 +64,6 @@ fn fixture(input: PathBuf) {
                                         no_document_all: loose,
                                         private_as_properties: loose,
                                         pure_getter: loose,
-                                        static_blocks_mark: Mark::new(),
                                     },
                                     unresolved_mark,
                                 ),
@@ -84,7 +83,6 @@ fn fixture(input: PathBuf) {
                                         no_document_all: loose,
                                         private_as_properties: loose,
                                         pure_getter: loose,
-                                        static_blocks_mark: Mark::new(),
                                     },
                                     unresolved_mark,
                                 ),

crates/swc_ecma_transforms_compat/tests/es2022_static_blocks.rs

@@ -22,13 +22,13 @@ fn fixture(input: PathBuf) {
             let pass: Box<dyn Pass> = if input.to_string_lossy().contains("class-properties") {
                 Box::new((
                     resolver(unresolved_mark, top_level_mark, false),
-                    static_blocks(config.static_blocks_mark),
+                    static_blocks(),
                     class_properties(config, unresolved_mark),
                 ))
             } else {
                 Box::new((
                     resolver(unresolved_mark, top_level_mark, false),
-                    static_blocks(config.static_blocks_mark),
+                    static_blocks(),
                 ))
             };
             pass

crates/swc_ecma_transforms_proposal/src/decorator_impl.rs

@@ -278,7 +278,7 @@ impl DecoratorPass {
                 }
             },
             _ => {
-                let key_ident = private_ident!("_computedKey");
+                let key_ident = private_ident!(name.span(), "_computedKey");
                 self.extra_vars.push(VarDeclarator {
                     span: DUMMY_SP,
                     name: key_ident.clone().into(),

crates/swc_ecma_transforms_proposal/tests/decorators.rs

@@ -133,9 +133,7 @@ fn create_pass(comments: Rc<SingleThreadedComments>, input: &Path) -> Box<dyn Pa
         match plugin {
             BabelPluginEntry::NameOnly(name) => match &**name {
                 "proposal-class-properties" => {
-                    add!(swc_ecma_transforms_compat::es2022::static_blocks(
-                        static_block_mark
-                    ));
+                    add!(swc_ecma_transforms_compat::es2022::static_blocks());
                     add!(swc_ecma_transforms_compat::es2022::class_properties(
                         Default::default(),
                         unresolved_mark
@@ -152,9 +150,7 @@ fn create_pass(comments: Rc<SingleThreadedComments>, input: &Path) -> Box<dyn Pa
                 }
 
                 "proposal-class-static-block" => {
-                    add!(swc_ecma_transforms_compat::es2022::static_blocks(
-                        static_block_mark
-                    ));
+                    add!(swc_ecma_transforms_compat::es2022::static_blocks());
                     continue;
                 }
                 _ => {}

crates/swc_ecma_transforms_proposal/tests/decorators/2022-03-accessors--to-es2015/private/output.js

@@ -21,33 +21,30 @@ class Foo {
         });
     }
 }
-var __ = {
-    writable: true,
-    value: { e: [_init_a, _get___a, _set___a, _init_b, _get___b, _set___b, _initProto] } = _apply_decs_2203_r(Foo, [
-        [
-            dec,
-            1,
-            "a",
-            function() {
-                return _class_private_field_get(this, ___a_1);
-            },
-            function(_v) {
-                _class_private_field_set(this, ___a_1, _v);
-            }
-        ],
-        [
-            dec,
-            1,
-            "b",
-            function() {
-                return _class_private_field_get(this, ___b_2);
-            },
-            function(_v) {
-                _class_private_field_set(this, ___b_2, _v);
-            }
-        ]
-    ], [])
-};
+({ e: [_init_a, _get___a, _set___a, _init_b, _get___b, _set___b, _initProto] } = _apply_decs_2203_r(Foo, [
+    [
+        dec,
+        1,
+        "a",
+        function() {
+            return _class_private_field_get(this, ___a_1);
+        },
+        function(_v) {
+            _class_private_field_set(this, ___a_1, _v);
+        }
+    ],
+    [
+        dec,
+        1,
+        "b",
+        function() {
+            return _class_private_field_get(this, ___b_2);
+        },
+        function(_v) {
+            _class_private_field_set(this, ___b_2, _v);
+        }
+    ]
+], []));
 function get_a() {
     return _get___a(this);
 }

crates/swc_ecma_transforms_proposal/tests/decorators/2022-03-accessors--to-es2015/public/output.js

@@ -37,23 +37,20 @@ class Foo {
         });
     }
 }
-var __ = {
-    writable: true,
-    value: { e: [_init_a, _init_b, _init_computedKey, _initProto] } = _apply_decs_2203_r(Foo, [
-        [
-            dec,
-            1,
-            "a"
-        ],
-        [
-            dec,
-            1,
-            "b"
-        ],
-        [
-            dec,
-            1,
-            _computedKey
-        ]
-    ], [])
-};
+({ e: [_init_a, _init_b, _init_computedKey, _initProto] } = _apply_decs_2203_r(Foo, [
+    [
+        dec,
+        1,
+        "a"
+    ],
+    [
+        dec,
+        1,
+        "b"
+    ],
+    [
+        dec,
+        1,
+        _computedKey
+    ]
+], []));