fix(es/compat): Fix this in computed class method names (#6364)

crates/swc/tests/tsc-references/computedPropertyNames21_ES5.1.normal.js

@@ -1,6 +1,6 @@
 //// [computedPropertyNames21_ES5.ts]
 import _class_call_check from "@swc/helpers/src/_class_call_check.mjs";
-var C = /*#__PURE__*/ function() {
+var C = /*#__PURE__*/ function(_prop) {
     "use strict";
     function C() {
         _class_call_check(this, C);
@@ -9,6 +9,6 @@ var C = /*#__PURE__*/ function() {
     _proto.bar = function bar() {
         return 0;
     };
-    _proto[this.bar()] = function() {};
+    _proto[_prop] = function() {};
     return C;
-}();
+}(this.bar());

crates/swc/tests/tsc-references/computedPropertyNames21_ES5.2.minified.js

@@ -1,2 +1,3 @@
 //// [computedPropertyNames21_ES5.ts]
 import _class_call_check from "@swc/helpers/src/_class_call_check.mjs";
+this.bar();

crates/swc/tests/tsc-references/computedPropertyNames23_ES5.1.normal.js

@@ -1,7 +1,7 @@
 //// [computedPropertyNames23_ES5.ts]
 import _class_call_check from "@swc/helpers/src/_class_call_check.mjs";
 import _define_property from "@swc/helpers/src/_define_property.mjs";
-var C = /*#__PURE__*/ function() {
+var C = /*#__PURE__*/ function(_prop) {
     "use strict";
     function C() {
         _class_call_check(this, C);
@@ -10,6 +10,6 @@ var C = /*#__PURE__*/ function() {
     _proto.bar = function bar() {
         return 0;
     };
-    _proto[_define_property({}, this.bar(), 1)[0]] = function() {};
+    _proto[_prop] = function() {};
     return C;
-}();
+}(_define_property({}, this.bar(), 1)[0]);

crates/swc/tests/tsc-references/computedPropertyNames23_ES5.2.minified.js

@@ -1,3 +1,4 @@
 //// [computedPropertyNames23_ES5.ts]
 import _class_call_check from "@swc/helpers/src/_class_call_check.mjs";
 import _define_property from "@swc/helpers/src/_define_property.mjs";
+_define_property({}, this.bar(), 1)[0];

crates/swc_ecma_transforms_compat/src/es2015/classes/mod.rs

@@ -7,9 +7,9 @@ use swc_ecma_transforms_base::{helper, native::is_native, perf::Check};
 use swc_ecma_transforms_classes::super_field::SuperFieldAccessFolder;
 use swc_ecma_transforms_macros::fast_path;
 use swc_ecma_utils::{
-    alias_if_required, default_constructor, is_valid_ident, is_valid_prop_ident, prepend_stmt,
-    private_ident, prop_name_to_expr, quote_expr, quote_ident, quote_str, replace_ident,
-    ExprFactory, IdentExt, IsDirective, ModuleItemLike, StmtLike,
+    alias_if_required, contains_this_expr, default_constructor, is_valid_ident,
+    is_valid_prop_ident, prepend_stmt, private_ident, prop_name_to_expr, quote_expr, quote_ident,
+    quote_str, replace_ident, ExprFactory, IdentExt, IsDirective, ModuleItemLike, StmtLike,
 };
 use swc_ecma_visit::{
     as_folder, noop_visit_mut_type, noop_visit_type, Fold, Visit, VisitMut, VisitMutWith, VisitWith,
@@ -535,7 +535,6 @@ where
         let class_name = class_name.unwrap_or_else(|| quote_ident!("_class"));
         let mut stmts = vec![];
 
-        let mut priv_methods = vec![];
         let mut methods = vec![];
         let mut constructor = None;
         for member in class.body {
@@ -547,7 +546,9 @@ where
                         constructor = Some(c)
                     }
                 }
-                ClassMember::PrivateMethod(m) => priv_methods.push(m),
+                ClassMember::PrivateMethod(_) => unreachable!(
+                    "classes pass: private method\nclass_properties pass should remove this"
+                ),
                 ClassMember::Method(m) => methods.push(m),
 
                 ClassMember::ClassProp(..) => {
@@ -773,7 +774,6 @@ where
         }
 
         // convert class methods
-        // stmts.extend(self.fold_class_methods(class_name.clone(), priv_methods));
         stmts.extend(self.fold_class_methods(&class_name, &super_class_ident, methods));
 
         if stmts.first().map(|v| !v.is_use_strict()).unwrap_or(false) && !self.in_strict {
@@ -1009,11 +1009,13 @@ where
         for mut m in methods {
             let key = HashKey::from(&m.key);
             let key_is_pure = is_pure_prop_name(&m.key);
+            // class is always strict, however computed key is not part of class
+            let key_contain_this = !self.in_strict && contains_this_expr(&m.key);
             let key_prop = Box::new(m.key.clone());
             let computed = matches!(m.key, PropName::Computed(..));
             let prop_name = prop_name_to_expr(m.key);
 
-            let key_prop = if should_extract && !key_is_pure {
+            let key_prop = if should_extract && !key_is_pure || key_contain_this {
                 let ident = private_ident!("_prop");
 
                 self.params.push(ident.clone().into());

crates/swc_ecma_transforms_compat/tests/classes/issue-6356/input.js

@@ -0,0 +1,3 @@
+class x {
+    [this[0]]() {}
+}

crates/swc_ecma_transforms_compat/tests/classes/issue-6356/output.js

@@ -0,0 +1,13 @@
+let x = /*#__PURE__*/ function(_prop) {
+    "use strict";
+    function x() {
+        _classCallCheck(this, x);
+    }
+    _createClass(x, [
+        {
+            key: _prop,
+            value: function() {}
+        }
+    ]);
+    return x;
+}(this[0]);