destructuring assignment no longer uses a temporary variable for simple LHS

lib/nodes.js

@@ -154,6 +154,7 @@
     Base.prototype.isPureStatement = NO;
     Base.prototype.isComplex = YES;
     Base.prototype.topSensitive = NO;
+    Base.prototype.assigns = NO;
     return Base;
   })();
   exports.Expressions = (function() {
@@ -266,6 +267,9 @@
     Literal.prototype.isReserved = function() {
       return !!this.value.reserved;
     };
+    Literal.prototype.assigns = function(name) {
+      return name === this.value;
+    };
     Literal.prototype.compileNode = function(o) {
       var end, idt, val;
       idt = this.isStatement(o) ? this.idt() : '';
@@ -348,6 +352,9 @@
     Value.prototype.isComplex = function() {
       return this.base.isComplex() || this.hasProperties();
     };
+    Value.prototype.assigns = function(name) {
+      return !this.properties.length && this.base.assigns(name);
+    };
     Value.prototype.makeReturn = function() {
       return this.properties.length ? Value.__super__.makeReturn.call(this) : this.base.makeReturn();
     };
@@ -817,13 +824,7 @@
         for (i = 0, _len = (_ref2 = this.properties).length; i < _len; i++) {
           prop = _ref2[i];
           _result.push((function() {
-            join = ",\n";
-            if ((prop === lastNoncom) || (prop instanceof Comment)) {
-              join = "\n";
-            }
-            if (i === this.properties.length - 1) {
-              join = '';
-            }
+            join = i === this.properties.length - 1 ? '' : (prop === lastNoncom || prop instanceof Comment ? '\n' : ',\n');
             indent = prop instanceof Comment ? '' : this.idt(1);
             if (prop instanceof Value && prop.tags["this"]) {
               prop = new Assign(prop.properties[0].name, prop, 'object');
@@ -836,9 +837,19 @@
         return _result;
       }).call(this);
       props = props.join('');
-      obj = '{' + (props ? '\n' + props + '\n' + this.idt() : '') + '}';
+      obj = ("{" + (props ? '\n' + props + '\n' + this.idt() : '') + "}");
       return top ? ("(" + obj + ")") : obj;
     };
+    ObjectLiteral.prototype.assigns = function(name) {
+      var _i, _len, _ref2, prop;
+      for (_i = 0, _len = (_ref2 = this.properties).length; _i < _len; _i++) {
+        prop = _ref2[_i];
+        if (prop.assigns(name)) {
+          return true;
+        }
+      }
+      return false;
+    };
     return ObjectLiteral;
   })();
   exports.ArrayLiteral = (function() {
@@ -874,6 +885,16 @@
       objects = objects.join('');
       return 0 < objects.indexOf('\n') ? ("[\n" + (o.indent) + objects + "\n" + (this.tab) + "]") : ("[" + objects + "]");
     };
+    ArrayLiteral.prototype.assigns = function(name) {
+      var _i, _len, _ref2, obj;
+      for (_i = 0, _len = (_ref2 = this.objects).length; _i < _len; _i++) {
+        obj = _ref2[_i];
+        if (obj.assigns(name)) {
+          return true;
+        }
+      }
+      return false;
+    };
     return ArrayLiteral;
   })();
   exports.Class = (function() {
@@ -1024,7 +1045,7 @@
       return top || this.parenthetical ? val : ("(" + val + ")");
     };
     Assign.prototype.compilePatternMatch = function(o) {
-      var _len, _ref2, _ref3, accessClass, assigns, code, i, idx, isObject, obj, objects, olength, otop, splat, top, val, valVar, value;
+      var _len, _ref2, _ref3, accessClass, assigns, code, i, idx, isObject, obj, objects, olength, otop, ref, splat, top, val, valVar, value;
       if ((value = this.value).isStatement(o)) {
         value = Closure.wrap(value);
       }
@@ -1050,15 +1071,19 @@
       otop = merge(o, {
         top: true
       });
-      valVar = o.scope.freeVariable('ref');
-      assigns = [("" + valVar + " = " + (value.compile(o)))];
+      valVar = value.compile(o);
+      assigns = [];
       splat = false;
+      if (!IDENTIFIER.test(valVar) || this.variable.assigns(valVar)) {
+        assigns.push("" + (ref = o.scope.freeVariable('ref')) + " = " + valVar);
+        valVar = ref;
+      }
       for (i = 0, _len = objects.length; i < _len; i++) {
         obj = objects[i];
         idx = i;
         if (isObject) {
           if (obj instanceof Assign) {
-            _ref3 = [obj.value, obj.variable.base], obj = _ref3[0], idx = _ref3[1];
+            _ref3 = obj, idx = _ref3.variable.base, obj = _ref3.value;
           } else {
             idx = obj.tags["this"] ? obj.properties[0].name : obj;
           }
@@ -1095,6 +1120,9 @@
       val = this.value.compile(o);
       return "([].splice.apply(" + name + ", [" + from + ", " + to + "].concat(" + ref + " = " + val + ")), " + ref + ")";
     };
+    Assign.prototype.assigns = function(name) {
+      return this[this.context === 'object' ? 'value' : 'variable'].assigns(name);
+    };
     return Assign;
   })();
   exports.Code = (function() {
@@ -1221,16 +1249,16 @@
     Splat = (function() {
       function Splat(name) {
         Splat.__super__.constructor.call(this);
-        if (!name.compile) {
-          name = new Literal(name);
-        }
-        this.name = name;
+        this.name = name.compile ? name : new Literal(name);
         return this;
       };
       return Splat;
     })();
     __extends(Splat, Base);
     Splat.prototype.children = ['name'];
+    Splat.prototype.assigns = function(name) {
+      return this.name.assigns(name);
+    };
     Splat.prototype.compileNode = function(o) {
       return (this.index != null) ? this.compileParam(o) : this.name.compile(o);
     };
@@ -1611,16 +1639,16 @@
   exports.For = (function() {
     For = (function() {
       function For(_arg, source, _arg2, _arg3) {
-        var _ref2, _ref3;
+        var _ref2;
         this.index = _arg3;
         this.name = _arg2;
         this.body = _arg;
         For.__super__.constructor.call(this);
-        _ref2 = source, this.source = _ref2.source, this.guard = _ref2.guard, this.step = _ref2.step;
+        this.source = source.source, this.guard = source.guard, this.step = source.step;
         this.raw = !!source.raw;
         this.object = !!source.object;
         if (this.object) {
-          _ref3 = [this.index, this.name], this.name = _ref3[0], this.index = _ref3[1];
+          _ref2 = [this.index, this.name], this.name = _ref2[0], this.index = _ref2[1];
         }
         this.pattern = this.name instanceof Value;
         if (this.index instanceof Value) {
@@ -1772,16 +1800,16 @@
       return this;
     };
     Switch.prototype.compileNode = function(o) {
-      var _i, _j, _len, _len2, _ref2, _ref3, _ref4, block, code, condition, conditions, exprs, idt, pair;
+      var _i, _j, _len, _len2, _ref2, _ref3, block, code, condition, conditions, exprs, idt, pair;
       idt = (o.indent = this.idt(2));
       o.top = true;
       code = ("" + (this.tab) + "switch (" + (this.subject.compile(o)) + ") {");
       for (_i = 0, _len = (_ref2 = this.cases).length; _i < _len; _i++) {
         pair = _ref2[_i];
-        _ref3 = pair, conditions = _ref3[0], block = _ref3[1];
+        conditions = pair[0], block = pair[1];
         exprs = block.expressions;
-        for (_j = 0, _len2 = (_ref4 = flatten([conditions])).length; _j < _len2; _j++) {
-          condition = _ref4[_j];
+        for (_j = 0, _len2 = (_ref3 = flatten([conditions])).length; _j < _len2; _j++) {
+          condition = _ref3[_j];
           if (this.tags.subjectless) {
             condition = new Op('!!', new Parens(condition));
           }