refactor(es/minifier): Merge cond_init with reassigned (#6850)

**Description:**

And optimize the following situation
```js
export function genElement(el, state) {
    if ('slot' === el.tag) return el1 = el, genChildren(el1);
    if (el.component) {
        var el1
        return 999;
    }
}
```
which rarely happens in hand written JS, but is often generated by swc merge variable pass.

Author: Austaras

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

@@ -77,7 +77,7 @@ where
                 return;
             }
 
-            if usage.cond_init || usage.used_above_decl {
+            if usage.used_above_decl {
                 log_abort!("inline: [x] It's cond init or used before decl",);
                 return;
             }
@@ -188,7 +188,7 @@ where
                         .vars
                         .get(&id.to_id())
                         .filter(|a| {
-                            !a.reassigned() && a.declared && !a.cond_init && {
+                            !a.reassigned() && a.declared && {
                                 // Function declarations are hoisted
                                 //
                                 // As we copy expressions, this can cause a problem.
@@ -360,10 +360,7 @@ where
 
                     Expr::Ident(id) if !id.eq_ignore_span(ident) => {
                         if let Some(init_usage) = self.data.vars.get(&id.to_id()) {
-                            if init_usage.reassigned()
-                                || !init_usage.declared
-                                || init_usage.cond_init
-                            {
+                            if init_usage.reassigned() || !init_usage.declared {
                                 return;
                             }
                         }

crates/swc_ecma_minifier/src/program_data.rs

@@ -64,9 +64,6 @@ pub(crate) struct VarUsageInfo {
     /// The number of direct reference to this identifier.
     pub(crate) ref_count: u32,
 
-    /// `true` if a variable is conditionally initialized.
-    pub(crate) cond_init: bool,
-
     /// `false` if it's only used.
     pub(crate) declared: bool,
     pub(crate) declared_count: u32,
@@ -86,9 +83,8 @@ pub(crate) struct VarUsageInfo {
     /// - Update is counted as usage, but assign is not
     pub(crate) usage_count: u32,
 
-    /// The variable itself is modified.
-    reassigned_with_assignment: bool,
-    reassigned_with_var_decl: bool,
+    /// The variable itself is assigned after reference.
+    reassigned: bool,
     /// The variable itself or a property of it is modified.
     pub(crate) mutated: bool,
 
@@ -140,7 +136,6 @@ impl Default for VarUsageInfo {
         Self {
             inline_prevented: Default::default(),
             ref_count: Default::default(),
-            cond_init: Default::default(),
             declared: Default::default(),
             declared_count: Default::default(),
             declared_as_fn_param: Default::default(),
@@ -149,8 +144,7 @@ impl Default for VarUsageInfo {
             assign_count: Default::default(),
             mutation_by_call_count: Default::default(),
             usage_count: Default::default(),
-            reassigned_with_assignment: Default::default(),
-            reassigned_with_var_decl: Default::default(),
+            reassigned: Default::default(),
             mutated: Default::default(),
             has_property_access: Default::default(),
             has_property_mutation: Default::default(),
@@ -186,8 +180,7 @@ impl VarUsageInfo {
     }
 
     pub(crate) fn reassigned(&self) -> bool {
-        self.reassigned_with_assignment
-            || self.reassigned_with_var_decl
+        self.reassigned
             || (u32::from(self.var_initialized)
                 + u32::from(self.declared_as_catch_param)
                 + u32::from(self.declared_as_fn_param)
@@ -241,25 +234,27 @@ impl Storage for ProgramData {
                 Entry::Occupied(mut e) => {
                     e.get_mut().inline_prevented |= var_info.inline_prevented;
 
-                    e.get_mut().cond_init |= if !inited && e.get().var_initialized {
-                        true
-                    } else {
-                        var_info.cond_init
-                    };
                     if var_info.var_initialized {
                         if e.get().var_initialized || e.get().ref_count > 0 {
                             e.get_mut().assign_count += 1;
-                            e.get_mut().reassigned_with_assignment = true;
+                            e.get_mut().reassigned = true;
                         } else {
                             // If it is referred outside child scope, it will
                             // be marked as var_initialized false
                             e.get_mut().var_initialized = true;
                         }
+                    } else {
+                        // If it is inited in some other child scope, but referenced in
+                        // current child scope
+                        if !inited && e.get().var_initialized && var_info.ref_count > 0 {
+                            e.get_mut().reassigned = true
+                        }
                     }
+
                     e.get_mut().ref_count += var_info.ref_count;
 
-                    e.get_mut().reassigned_with_assignment |= var_info.reassigned_with_assignment;
-                    e.get_mut().reassigned_with_var_decl |= var_info.reassigned_with_var_decl;
+                    e.get_mut().reassigned |= var_info.reassigned;
+
                     e.get_mut().mutated |= var_info.mutated;
 
                     e.get_mut().has_property_access |= var_info.has_property_access;
@@ -359,7 +354,7 @@ impl Storage for ProgramData {
             }
 
             v.mutated = true;
-            v.reassigned_with_var_decl = true;
+            v.reassigned = true;
             v.assign_count += 1;
         }
 
@@ -458,8 +453,8 @@ impl VarDataLike for VarUsageInfo {
         self.mutated = true;
     }
 
-    fn mark_reassigned_with_assign(&mut self) {
-        self.reassigned_with_assignment = true;
+    fn mark_reassigned(&mut self) {
+        self.reassigned = true;
     }
 
     fn add_infects_to(&mut self, other: Access) {
@@ -625,11 +620,10 @@ impl ProgramData {
         if is_first {
             e.ref_count += 1;
             if !inited && e.var_initialized {
-                e.cond_init = true;
                 if !is_modify {
                     e.var_initialized = false;
                     e.assign_count += 1;
-                    e.reassigned_with_assignment = true
+                    e.reassigned = true
                 }
             }
         }
@@ -656,7 +650,7 @@ impl ProgramData {
                     e.assign_count -= 1;
                     e.var_initialized = true;
                 } else {
-                    e.reassigned_with_assignment = true
+                    e.reassigned = true
                 }
             }
 

crates/swc_ecma_minifier/tests/benches-full/echarts.js

@@ -26853,8 +26853,8 @@
         mousemove: function(e) {
             var x = e.offsetX, y = e.offsetY, localCursorPoint = this.group.transformCoordToLocal(x, y);
             if (!function(controller, e, localCursorPoint) {
-                if (!(!controller._brushType || (controller1 = controller, x = e.offsetX, y = e.offsetY, zr = controller1._zr, x < 0 || x > zr.getWidth() || y < 0 || y > zr.getHeight()))) {
-                    var controller1, x, y, zr, zr1 = controller._zr, covers = controller._covers, currPanel = getPanelByPoint(controller, e, localCursorPoint);
+                if (!(!controller._brushType || (x = e.offsetX, y = e.offsetY, zr = controller._zr, x < 0 || x > zr.getWidth() || y < 0 || y > zr.getHeight()))) {
+                    var x, y, zr, zr1 = controller._zr, covers = controller._covers, currPanel = getPanelByPoint(controller, e, localCursorPoint);
                     if (!controller._dragging) for(var i = 0; i < covers.length; i++){
                         var brushOption = covers[i].__brushOption;
                         if (currPanel && (!0 === currPanel || brushOption.panelId === currPanel.panelId) && coverRenderers[brushOption.brushType].contain(covers[i], localCursorPoint[0], localCursorPoint[1])) return;
@@ -36191,10 +36191,10 @@
                 'parallel' === seriesModel.subType ? (coordSys = seriesModel.coordinateSystem, hasBrushExists = hasBrushExists || coordSys.hasAxisBrushed(), linkOthers(seriesIndex) && coordSys.eachActiveState(seriesModel.getData(), function(activeState, dataIndex) {
                     'active' === activeState && (selectedDataIndexForLink[dataIndex] = 1);
                 })) : function(seriesModel, seriesIndex, rangeInfoList) {
-                    if (!(!seriesModel.brushSelector || (brushModel1 = brushModel, seriesIndex1 = seriesIndex, null != (seriesIndices = brushModel1.option.seriesIndex) && 'all' !== seriesIndices && (isArray(seriesIndices) ? 0 > indexOf(seriesIndices, seriesIndex1) : seriesIndex1 !== seriesIndices))) && (each(areas, function(area) {
+                    if (!(!seriesModel.brushSelector || null != (seriesIndices = brushModel.option.seriesIndex) && 'all' !== seriesIndices && (isArray(seriesIndices) ? 0 > indexOf(seriesIndices, seriesIndex) : seriesIndex !== seriesIndices)) && (each(areas, function(area) {
                         brushModel.brushTargetManager.controlSeries(area, seriesModel, ecModel) && rangeInfoList.push(area), hasBrushExists = hasBrushExists || brushed(rangeInfoList);
                     }), linkOthers(seriesIndex) && brushed(rangeInfoList))) {
-                        var brushModel1, seriesIndex1, seriesIndices, data_1 = seriesModel.getData();
+                        var seriesIndices, data_1 = seriesModel.getData();
                         data_1.each(function(dataIndex) {
                             checkInRange(seriesModel, rangeInfoList, data_1, dataIndex) && (selectedDataIndexForLink[dataIndex] = 1);
                         });
@@ -40856,8 +40856,8 @@
             return subOption = exprOption.not, errMsg = '', errMsg = makePrintable('"not" condition should only be `not: {}`.', 'Illegal condition:', exprOption), isObject(val = subOption) && !isArrayLike(val) || throwError(errMsg), (cond = new NotConditionInternal()).child = parseOption(subOption, getters), cond.child || throwError(errMsg), cond;
         }
         return function(exprOption, getters) {
-            for(var valueGetterParam = getters.prepareGetValue(exprOption), subCondList = [], exprKeys = keys(exprOption), parserName = exprOption.parser, valueParser = parserName ? (type = parserName, valueParserMap.get(type)) : null, i = 0; i < exprKeys.length; i++){
-                var type, keyRaw = exprKeys[i];
+            for(var valueGetterParam = getters.prepareGetValue(exprOption), subCondList = [], exprKeys = keys(exprOption), parserName = exprOption.parser, valueParser = parserName ? valueParserMap.get(parserName) : null, i = 0; i < exprKeys.length; i++){
+                var keyRaw = exprKeys[i];
                 if (!('parser' === keyRaw || getters.valueGetterAttrMap.get(keyRaw))) {
                     var op = hasOwn(RELATIONAL_EXPRESSION_OP_ALIAS_MAP, keyRaw) ? RELATIONAL_EXPRESSION_OP_ALIAS_MAP[keyRaw] : keyRaw, condValueRaw = exprOption[keyRaw], condValueParsed = valueParser ? valueParser(condValueRaw) : condValueRaw, evaluator = ('eq' === op || 'ne' === op ? new FilterEqualityComparator('eq' === op, condValueParsed) : hasOwn(ORDER_COMPARISON_OP_MAP, op) ? new FilterOrderComparator(op, condValueParsed) : null) || 'reg' === op && new RegExpEvaluator(condValueParsed);
                     evaluator || throwError(makePrintable('Illegal relational operation: "' + keyRaw + '" in condition:', exprOption)), subCondList.push(evaluator);

crates/swc_ecma_minifier/tests/benches-full/lodash.js

@@ -627,9 +627,9 @@
             if (!isObject(value)) return value;
             var isArr = isArray(value);
             if (isArr) {
-                if (length = (array = value).length, result1 = new array.constructor(length), length && 'string' == typeof array[0] && hasOwnProperty.call(array, 'index') && (result1.index = array.index, result1.input = array.input), result = result1, !isDeep) return copyArray(value, result);
+                if (length = value.length, result1 = new value.constructor(length), length && 'string' == typeof value[0] && hasOwnProperty.call(value, 'index') && (result1.index = value.index, result1.input = value.input), result = result1, !isDeep) return copyArray(value, result);
             } else {
-                var array, length, result1, object1, object2, object3, tag = getTag(value), isFunc = tag == funcTag || tag == genTag;
+                var length, result1, object1, object2, object3, tag = getTag(value), isFunc = tag == funcTag || tag == genTag;
                 if (isBuffer(value)) return cloneBuffer(value, isDeep);
                 if (tag == objectTag || tag == argsTag || isFunc && !object) {
                     if (result = isFlat || isFunc ? {} : initCloneObject(value), !isDeep) return isFlat ? (object1 = (object3 = result) && copyObject(value, keysIn(value), object3), copyObject(value, getSymbolsIn(value), object1)) : (object2 = baseAssign(result, value), copyObject(value, getSymbols(value), object2));

crates/swc_ecma_minifier/tests/benches-full/vue.js

@@ -2626,14 +2626,14 @@
                     var id = "__transition-" + this._uid + "-";
                     child.key = null == child.key ? child.isComment ? id + 'comment' : id + child.tag : isPrimitive(child.key) ? 0 === String(child.key).indexOf(id) ? child.key : id + child.key : child.key;
                     var data = (child.data || (child.data = {})).transition = extractTransitionData(this), oldRawChild = this._vnode, oldChild = getRealChild(oldRawChild);
-                    if (child.data.directives && child.data.directives.some(isVShowDirective) && (child.data.show = !0), oldChild && oldChild.data && (child1 = child, (oldChild1 = oldChild).key !== child1.key || oldChild1.tag !== child1.tag) && !isAsyncPlaceholder(oldChild) && !(oldChild.componentInstance && oldChild.componentInstance._vnode.isComment)) {
+                    if (child.data.directives && child.data.directives.some(isVShowDirective) && (child.data.show = !0), oldChild && oldChild.data && (oldChild.key !== child.key || oldChild.tag !== child.tag) && !isAsyncPlaceholder(oldChild) && !(oldChild.componentInstance && oldChild.componentInstance._vnode.isComment)) {
                         var oldData = oldChild.data.transition = extend({}, data);
                         if ('out-in' === mode) return this._leaving = !0, mergeVNodeHook(oldData, 'afterLeave', function() {
                             this$1._leaving = !1, this$1.$forceUpdate();
                         }), placeholder(h, rawChild);
                         if ('in-out' === mode) {
                             if (isAsyncPlaceholder(child)) return oldRawChild;
-                            var child1, oldChild1, delayedLeave, performLeave = function() {
+                            var delayedLeave, performLeave = function() {
                                 delayedLeave();
                             };
                             mergeVNodeHook(data, 'afterEnter', performLeave), mergeVNodeHook(data, 'enterCancelled', performLeave), mergeVNodeHook(oldData, 'delayLeave', function(leave) {
@@ -3092,17 +3092,17 @@
         if (el.for && !el.forProcessed) return genFor(el, state);
         if (el.if && !el.ifProcessed) return genIf(el, state);
         if ('template' === el.tag && !el.slotTarget && !state.pre) return genChildren(el, state) || 'void 0';
-        if ('slot' === el.tag) return el1 = el, state1 = state, res = "_t(" + (el1.slotName || '"default"') + ((children = genChildren(el1, state1)) ? "," + children : ''), attrs = el1.attrs || el1.dynamicAttrs ? genProps((el1.attrs || []).concat(el1.dynamicAttrs || []).map(function(attr) {
+        if ('slot' === el.tag) return res = "_t(" + (el.slotName || '"default"') + ((children = genChildren(el, state)) ? "," + children : ''), attrs = el.attrs || el.dynamicAttrs ? genProps((el.attrs || []).concat(el.dynamicAttrs || []).map(function(attr) {
             return {
                 name: camelize(attr.name),
                 value: attr.value,
                 dynamic: attr.dynamic
             };
-        })) : null, bind$$1 = el1.attrsMap['v-bind'], (attrs || bind$$1) && !children && (res += ",null"), attrs && (res += "," + attrs), bind$$1 && (res += (attrs ? '' : ',null') + "," + bind$$1), res + ')';
-        if (el.component) componentName = el.component, el2 = el, state2 = state, children1 = el2.inlineTemplate ? null : genChildren(el2, state2, !0), code = "_c(" + componentName + "," + genData$2(el2, state2) + (children1 ? "," + children1 : '') + ")";
+        })) : null, bind$$1 = el.attrsMap['v-bind'], (attrs || bind$$1) && !children && (res += ",null"), attrs && (res += "," + attrs), bind$$1 && (res += (attrs ? '' : ',null') + "," + bind$$1), res + ')';
+        if (el.component) componentName = el.component, children1 = el.inlineTemplate ? null : genChildren(el, state, !0), code = "_c(" + componentName + "," + genData$2(el, state) + (children1 ? "," + children1 : '') + ")";
         else {
             (!el.plain || el.pre && state.maybeComponent(el)) && (data = genData$2(el, state));
-            var el1, state1, children, res, attrs, bind$$1, code, componentName, el2, state2, children1, data, children2 = el.inlineTemplate ? null : genChildren(el, state, !0);
+            var children, res, attrs, bind$$1, code, componentName, children1, data, children2 = el.inlineTemplate ? null : genChildren(el, state, !0);
             code = "_c('" + el.tag + "'" + (data ? "," + data : '') + (children2 ? "," + children2 : '') + ")";
         }
         for(var i = 0; i < state.transforms.length; i++)code = state.transforms[i](el, code);