fix(es/minifier): Fix a bug related to inliner and the variable scoping

crates/swc/tests/fixture/issues-5xxx/5865/output/index.js

@@ -1 +1 @@
-var a;v=(a=r,b=>a.map(t=>{if(t)return t.foo}));
+let a;v=(a=r,b=>a.map(t=>{if(t)return t.foo}));

crates/swc/tests/fixture/issues-8xxx/8246/input/.swcrc

@@ -0,0 +1,73 @@
+{
+    "jsc": {
+        "parser": {
+            "syntax": "ecmascript",
+            "jsx": true
+        },
+        "transform": null,
+        "target": "es2015",
+        "loose": true,
+        "externalHelpers": false,
+        "minify": {
+            "mangle": {
+                "toplevel": false,
+                "keep_classnames": false,
+                "keep_fnames": false,
+                "keep_private_props": false,
+                "ie8": false,
+                "safari10": false
+            },
+            "compress": {
+                "arguments": false,
+                "arrows": true,
+                "booleans": true,
+                "booleans_as_integers": false,
+                "collapse_vars": true,
+                "comparisons": true,
+                "computed_props": true,
+                "conditionals": true,
+                "dead_code": true,
+                "directives": true,
+                "drop_console": false,
+                "drop_debugger": true,
+                "evaluate": true,
+                "expression": false,
+                "hoist_funs": false,
+                "hoist_props": true,
+                "hoist_vars": false,
+                "if_return": true,
+                "join_vars": true,
+                "keep_classnames": false,
+                "keep_fargs": true,
+                "keep_fnames": false,
+                "keep_infinity": false,
+                "loops": true,
+                "negate_iife": true,
+                "properties": true,
+                "reduce_funcs": false,
+                "reduce_vars": false,
+                "side_effects": true,
+                "switches": true,
+                "typeofs": true,
+                "unsafe": false,
+                "unsafe_arrows": false,
+                "unsafe_comps": false,
+                "unsafe_Function": false,
+                "unsafe_math": false,
+                "unsafe_symbols": false,
+                "unsafe_methods": false,
+                "unsafe_proto": false,
+                "unsafe_regexp": false,
+                "unsafe_undefined": false,
+                "unused": true,
+                "const_to_let": true,
+                "pristine_globals": true
+            }
+        }
+    },
+    "module": {
+        "type": "commonjs"
+    },
+    "isModule": false,
+    "minify": false
+}

crates/swc/tests/fixture/issues-8xxx/8246/input/input.js

@@ -0,0 +1,24 @@
+function withLog(methods) {
+    const result = {}
+    for (const methodName in methods) {
+        result[methodName] = ((methodName) => function () {
+            console.log(methodName + ' invoked')
+            return methods[methodName].apply(this, arguments)
+        })(methodName)
+    }
+    return result
+}
+
+function main() {
+    const result = withLog({
+        test() {
+            console.log('method test executed')
+        },
+        another() {
+            console.log('method another executed')
+        }
+    })
+
+    result.test()
+}
+main()

crates/swc/tests/fixture/issues-8xxx/8246/output/input.js

@@ -0,0 +1,21 @@
+function withLog(t) {
+    let e = {};
+    for(let o in t){
+        let n;
+        e[o] = (n = o, function() {
+            return console.log(n + ' invoked'), t[n].apply(this, arguments);
+        });
+    }
+    return e;
+}
+function main() {
+    withLog({
+        test () {
+            console.log('method test executed');
+        },
+        another () {
+            console.log('method another executed');
+        }
+    }).test();
+}
+main();

crates/swc_ecma_minifier/src/compress/optimize/iife.rs

@@ -519,7 +519,7 @@ impl Optimizer<'_> {
                             self.prepend_stmts.push(
                                 VarDecl {
                                     span: DUMMY_SP,
-                                    kind: VarDeclKind::Var,
+                                    kind: VarDeclKind::Let,
                                     declare: Default::default(),
                                     decls: vars,
                                 }

crates/swc_ecma_minifier/tests/exec.rs

@@ -11111,3 +11111,84 @@ fn issue_8119_2() {
         false,
     );
 }
+
+#[test]
+fn issue_8246_1() {
+    run_exec_test(
+        r#"
+        function withLog(methods) {
+            const result = {};
+            for(const methodName in methods){
+                result[methodName] = ((methodName)=>function() {
+                        console.log(methodName + ' invoked');
+                        return methods[methodName].apply(this, arguments);
+                    })(methodName);
+            }
+            return result;
+        }
+        function main() {
+            const result = withLog({
+                test () {
+                    console.log('method test executed');
+                },
+                another () {
+                    console.log('method another executed');
+                }
+            });
+            result.test();
+        }
+        main();
+        "#,
+        r#"
+        {
+            "ecma": 2015,
+            "arguments": false,
+            "arrows": true,
+            "booleans": true,
+            "booleans_as_integers": false,
+            "collapse_vars": true,
+            "comparisons": true,
+            "computed_props": true,
+            "conditionals": true,
+            "dead_code": true,
+            "directives": true,
+            "drop_console": false,
+            "drop_debugger": true,
+            "evaluate": true,
+            "expression": false,
+            "hoist_funs": false,
+            "hoist_props": true,
+            "hoist_vars": false,
+            "if_return": true,
+            "join_vars": true,
+            "keep_classnames": false,
+            "keep_fargs": true,
+            "keep_fnames": false,
+            "keep_infinity": false,
+            "loops": true,
+            "negate_iife": true,
+            "properties": true,
+            "reduce_funcs": false,
+            "reduce_vars": false,
+            "side_effects": true,
+            "switches": true,
+            "typeofs": true,
+            "unsafe": false,
+            "unsafe_arrows": false,
+            "unsafe_comps": false,
+            "unsafe_Function": false,
+            "unsafe_math": false,
+            "unsafe_symbols": false,
+            "unsafe_methods": false,
+            "unsafe_proto": false,
+            "unsafe_regexp": false,
+            "unsafe_undefined": false,
+            "unused": true,
+            "const_to_let": true,
+            "pristine_globals": true,
+            "passes": 5
+        }
+        "#,
+        false,
+    );
+}