fix(es/minifier): Fix a bug related to inliner and the variable scoping (#8542)

**Related issue:**

 - Closes #8246

Author: kdy1

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,
+    );
+}

crates/swc_ecma_minifier/tests/fixture/next/47005/output.js

@@ -5,12 +5,13 @@
     {
         9145: function(m, S, h) {
             "use strict";
+            let E, k;
             h.d(S, {
                 u: function() {
                     return eu;
                 }
             });
-            var E, k, R, A = h(7294);
+            var R, A = h(7294);
             var O = h(5893);
             var L = Object.create;
             var j = Object.defineProperty;

crates/swc_ecma_minifier/tests/fixture/next/outstatic/1/output.js

@@ -6,28 +6,28 @@
         1973: function(module) {
             eval(module.code);
         },
-        1985: function(n, t, e) {
+        1985: function(t, e, n) {
             "use strict";
-            var c = 0, r = (n)=>"checkbox" === n.type;
-            var u = (n, t)=>{
-                var e;
-                return n.has((e = t).substring(0, e.search(/\.\d+(\.|$)/)) || e);
+            var c = 0, r = (t)=>"checkbox" === t.type;
+            var u = (t, e)=>{
+                let n;
+                return t.has((n = e).substring(0, n.search(/\.\d+(\.|$)/)) || n);
             }, o = ()=>{};
-            function s(n, t, e) {}
-            var a = (n)=>"radio" === n.type;
-            function f(n = {}) {
-                let t, e = {
-                    ...n
+            function s(t, e, n) {}
+            var a = (t)=>"radio" === t.type;
+            function f(t = {}) {
+                let e, n = {
+                    ...t
                 }, c = {}, r = 0, u = {}, o = {};
-                const s = 0, a = async (n)=>{
-                    let t = n.target.name;
-                    const e = 0;
+                const s = 0, a = async (t)=>{
+                    let e = t.target.name;
+                    const n = 0;
                 };
             }
-            t.useForm = function(n = {}) {
-                const t = c.default.useRef();
-                t.current ? t.current.control._options = n : t.current = {
-                    ...f(n)
+            e.useForm = function(t = {}) {
+                const e = c.default.useRef();
+                e.current ? e.current.control._options = t : e.current = {
+                    ...f(t)
                 };
             };
         }

crates/swc_ecma_minifier/tests/terser/compress/identity/inline_identity_dont_lose_this_when_arg/output.js

@@ -2,5 +2,5 @@
 const func_bag = {
     leak: leak
 };
-var x;
+let x;
 leak(x = func_bag.leak);

crates/swc_ecma_minifier/tests/terser/compress/identity/inline_identity_lose_this/output.js

@@ -8,7 +8,7 @@ const func_bag = {
 func_bag.func2 = function() {
     return void 0 === this ? "PASS" : "FAIL";
 };
-var x;
+let x;
 console.log((x = func_bag.func)());
-var x1;
+let x1;
 console.log((x1 = func_bag.func2)());