feat(es/minifier): Drop recursively used var declaration (#7649)

Author: Austaras

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

@@ -1,11 +1,4 @@
 //// [assignmentCompatWithObjectMembers.ts]
 var SimpleTypes, ObjectTypes;
 import "@swc/helpers/_/_class_call_check";
-SimpleTypes || (SimpleTypes = {}), function(ObjectTypes) {
-    var t2, b, a2 = {
-        foo: a2
-    }, b2 = {
-        foo: b2
-    };
-    b2 = a2 = b2, a2 = b, a2 = t2;
-}(ObjectTypes || (ObjectTypes = {}));
+SimpleTypes || (SimpleTypes = {}), ObjectTypes || (ObjectTypes = {});

crates/swc/tests/tsc-references/destructuringArrayBindingPatternAndAssignment3.2.minified.js

@@ -1,15 +1,13 @@
 //// [destructuringArrayBindingPatternAndAssignment3.ts]
 import { _ as _sliced_to_array } from "@swc/helpers/_/_sliced_to_array";
-var tmp2 = [
-    1
-][2], e = void 0 === tmp2 ? e : tmp2;
 !function(param) {
     var _param = _sliced_to_array(param, 2);
     _param[0], _param[1];
 }([
     1
 ]), function(param) {
-    var _param = _sliced_to_array(param, 3), tmp1 = (_param[0], _param[1], _param[2]), e = void 0 === tmp1 ? e : tmp1;
+    var _param = _sliced_to_array(param, 3);
+    _param[0], _param[1], _param[2];
 }([
     1
 ]), function(param) {

crates/swc/tests/tsc-references/destructuringObjectBindingPatternAndAssignment1ES5.2.minified.js

@@ -1,13 +1,11 @@
 //// [destructuringObjectBindingPatternAndAssignment1ES5.ts]
 (void 0).a1;
 var tmp = {};
-(void 0 === tmp ? {
-    b21: "string"
-} : tmp).b21;
-var b52 = b52;
 function foo1() {
     return {
         prop1: 2
     };
 }
-foo1().prop1, foo1().prop2;
+(void 0 === tmp ? {
+    b21: "string"
+} : tmp).b21, foo1().prop1, foo1().prop2;

crates/swc/tests/tsc-references/destructuringObjectBindingPatternAndAssignment4.2.minified.js

@@ -1,2 +1,3 @@
 //// [destructuringObjectBindingPatternAndAssignment4.ts]
-var _ref = {}, _ref_f = (_ref.a, _ref.b, _ref.c, _ref.d, _ref.e, _ref.f), f = void 0 === _ref_f ? f : _ref_f;
+var _ref = {};
+_ref.a, _ref.b, _ref.c, _ref.d, _ref.e, _ref.f;

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

@@ -1,9 +1 @@
 //// [objectLiteralShorthandProperties.ts]
-var x3 = {
-    a: 0,
-    b: void 0,
-    c: void 0,
-    d: function() {},
-    x3: x3,
-    parent: x3
-};

crates/swc/tests/tsc-references/objectLiteralShorthandPropertiesES6.2.minified.js

@@ -1,9 +1 @@
 //// [objectLiteralShorthandPropertiesES6.ts]
-var x3 = {
-    a: 0,
-    b: void 0,
-    c: void 0,
-    d () {},
-    x3,
-    parent: x3
-};

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

@@ -1,2 +1,2 @@
 //// [recursiveInitializer.ts]
-var n1 = n1++, n2 = n2 + n2, n3 = n3 + n3, s1 = s1 + "", s2 = s2 + s2, s3 = s3 + s3, s4 = "" + s4, b1 = !b1, b2 = !!b2, b3 = !b3 || b3, b4 = !b4 && b4;
+var n1 = n1++;

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

@@ -1,18 +1,15 @@
 //// [witness.ts]
 import { _ as _class_call_check } from "@swc/helpers/_/_class_call_check";
-var co2, cnd1, or1, or2, or3, and1, and3, propAcc1, M2, varInit = varInit;
 !function fnReturn1() {
     return fnReturn1();
 }(), function fnReturn2() {
     return fnReturn2;
-}();
-var co2 = co2, cnd1 = cnd1 ? 0 : 1, or1 = or1 || "", or2 = or2, or3 = or3 || or3, and1 = and1 && "", and3 = and3 && and3;
-!function fnCall() {
+}(), function fnCall() {
     return fnCall();
 }(), function fn5() {
     return new (void 0)(fn5);
 }();
-var propAcc1 = {
+var propAcc1, M2, propAcc1 = {
     m: propAcc1.m
 };
 (M2 || (M2 = {})).x = M2.x, new function C2() {

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

@@ -176,6 +176,10 @@ impl Optimizer<'_> {
                 self.mode.store(ident.to_id(), &*init);
             }
 
+            if usage.used_recursively {
+                return;
+            }
+
             // Caution: for most case mutation of properties are ok, however if
             // new variant is added for multi inline, think carefully
             if is_inline_enabled
@@ -308,7 +312,7 @@ impl Optimizer<'_> {
                 && ref_count == 1
             {
                 match init {
-                    Expr::Fn(FnExpr { function: f, .. }) | Expr::Fn(FnExpr { function: f, .. })
+                    Expr::Fn(FnExpr { function: f, .. })
                         if matches!(
                             &**f,
                             Function { is_async: true, .. }

crates/swc_ecma_minifier/tests/fixture/issues/7641/1/input.js

@@ -0,0 +1 @@
+let a = () => a

crates/swc_ecma_minifier/tests/fixture/issues/7641/1/output.js

@@ -1 +1 @@
-[](function(){var n=function(){n[b]}});
+[](function(){});

crates/swc_ecma_minifier/tests/full/size/37f0ab9950257024a9116d933f4ad3c72b88471e/output.js

@@ -1 +1 @@
-[](function(){var n=function(){0(function(){return n})}});
+[](function(){});

crates/swc_ecma_minifier/tests/full/size/3b335e237f275bec488d72f8934589b74346a0c1/output.js

@@ -1 +1 @@
-[](function(){var n=function(){b(function(){b(n)})}});
+[](function(){});

crates/swc_ecma_minifier/tests/full/size/3f1b1f240dbfc9585d82094d944515c068eac6dc/output.js

@@ -1 +1 @@
-[](function(){var n=function(){n.b}});
+[](function(){});

crates/swc_ecma_minifier/tests/full/size/4dfc0f7ca994bdaddd4ac283d2bb75a232047f70/output.js

@@ -1 +1 @@
-[](function(){var n;n=function(){b(n)}});
+[](function(){});

crates/swc_ecma_minifier/tests/full/size/b57e4ca6d118a9480312f6f3ac809245bbed8115/output.js

@@ -1 +1 @@
-[](function(){var n=function(){b(n)}});
+[](function(){});

crates/swc_ecma_minifier/tests/full/size/cb3806c635e59c15d84ee6c6cae3db9c9fce06cc/output.js

@@ -1,12 +1,2 @@
-function f1() {
-    var self = {
-        inner: function() {
-            return self;
-        }
-    };
-}
-function f2() {
-    var self = {
-        inner: self
-    };
-}
+function f1() {}
+function f2() {}

crates/swc_ecma_minifier/tests/terser/compress/collapse_vars/collapse_vars_self_reference/output.js

@@ -1,7 +1,7 @@
 use swc_atoms::js_word;
 use swc_common::{collections::AHashMap, Mark, SyntaxContext};
 use swc_ecma_ast::*;
-use swc_ecma_utils::{find_pat_ids, ExprCtx, IsEmpty, StmtExt};
+use swc_ecma_utils::{find_pat_ids, ExprCtx, ExprExt, IsEmpty, StmtExt};
 use swc_ecma_visit::{noop_visit_type, Visit, VisitWith};
 use swc_timer::timer;
 
@@ -1261,14 +1261,18 @@ where
             if self.marks.is_some() {
                 if let VarDeclarator {
                     name: Pat::Ident(id),
-                    init: Some(..),
+                    init: Some(init),
                     definite: false,
                     ..
                 } = e
                 {
                     let id = id.to_id();
-                    self.used_recursively
-                        .insert(id.clone(), RecursiveUsage::Var { can_ignore: false });
+                    self.used_recursively.insert(
+                        id.clone(),
+                        RecursiveUsage::Var {
+                            can_ignore: !init.may_have_side_effects(&self.expr_ctx),
+                        },
+                    );
                     e.init.visit_with(&mut *self.with_ctx(ctx));
                     self.used_recursively.remove(&id);
                     return;

crates/swc_ecma_usage_analyzer/src/analyzer/mod.rs

@@ -54,7 +54,7 @@
             alert('test')
         </script>
     </math>
-    <script blocking="a render">console.log("block")</script><script>!function(t){var t="test"+Math.random()+t;alert("1 "+(2+Math.random())),console.log(Math.random())}("test"),window.jQuery||document.write('<script src="jquery.js"><\/script>')</script>
+    <script blocking="a render">console.log("block")</script><script>!function(r){var r=Math.random();alert("1 "+(2+Math.random())),console.log(Math.random())}(0),window.jQuery||document.write('<script src="jquery.js"><\/script>')</script>
     <div>test</div>
 
     <div>topLevel - script</div>