destructuring assignment no longer uses a temporary variable for simple LHS

lib/lexer.js

@@ -30,11 +30,11 @@
       return (new Rewriter).rewrite(this.tokens);
     };
     Lexer.prototype.identifierToken = function() {
-      var _ref2, colon, forcedIdentifier, id, input, match, tag;
+      var colon, forcedIdentifier, id, input, match, tag;
       if (!(match = IDENTIFIER.exec(this.chunk))) {
         return false;
       }
-      _ref2 = match, input = _ref2[0], id = _ref2[1], colon = _ref2[2];
+      input = match[0], id = match[1], colon = match[2];
       this.i += input.length;
       if (id === 'all' && this.tag() === 'FOR') {
         this.token('ALL', id);
@@ -153,11 +153,11 @@
       return true;
     };
     Lexer.prototype.commentToken = function() {
-      var _ref2, comment, here, match;
+      var comment, here, match;
       if (!(match = this.chunk.match(COMMENT))) {
         return false;
       }
-      _ref2 = match, comment = _ref2[0], here = _ref2[1];
+      comment = match[0], here = match[1];
       this.line += count(comment, '\n');
       this.i += comment.length;
       if (here) {
@@ -197,8 +197,8 @@
       return true;
     };
     Lexer.prototype.heregexToken = function(match) {
-      var _i, _len, _ref2, _ref3, _ref4, _ref5, _this, body, flags, heregex, re, tag, tokens, value;
+      var _i, _len, _ref2, _ref3, _ref4, _this, body, flags, heregex, re, tag, tokens, value;
-      _ref2 = match, heregex = _ref2[0], body = _ref2[1], flags = _ref2[2];
+      heregex = match[0], body = match[1], flags = match[2];
       this.i += heregex.length;
       if (0 > body.indexOf('#{')) {
         re = body.replace(HEREGEX_OMIT, '').replace(/\//g, '\\/');
@@ -208,10 +208,10 @@
       this.token('IDENTIFIER', 'RegExp');
       this.tokens.push(['CALL_START', '(']);
       tokens = [];
-      for (_i = 0, _len = (_ref3 = this.interpolateString(body, {
+      for (_i = 0, _len = (_ref2 = this.interpolateString(body, {
         regex: true
       })).length; _i < _len; _i++) {
-        _ref4 = _ref3[_i], tag = _ref4[0], value = _ref4[1];
+        _ref3 = _ref2[_i], tag = _ref3[0], value = _ref3[1];
         if (tag === 'TOKENS') {
           tokens.push.apply(tokens, value);
         } else {
@@ -224,7 +224,7 @@
         tokens.push(['+', '+']);
       }
       tokens.pop();
-      if ((((_ref5 = tokens[0]) != null) ? _ref5[0] : undefined) !== 'STRING') {
+      if ((((_ref4 = tokens[0]) != null) ? _ref4[0] : undefined) !== 'STRING') {
         this.tokens.push(['STRING', '""'], ['+', '+']);
       }
       (_this = this.tokens).push.apply(_this, tokens);
@@ -399,15 +399,15 @@
       return true;
     };
     Lexer.prototype.sanitizeHeredoc = function(doc, options) {
-      var _ref2, _ref3, attempt, herecomment, indent, match;
+      var _ref2, attempt, herecomment, indent, match;
-      _ref2 = options, indent = _ref2.indent, herecomment = _ref2.herecomment;
+      indent = options.indent, herecomment = options.herecomment;
       if (herecomment && 0 > doc.indexOf('\n')) {
         return doc;
       }
       if (!herecomment) {
         while (match = HEREDOC_INDENT.exec(doc)) {
           attempt = match[1];
-          if (indent === null || (0 < (_ref3 = attempt.length)) && (_ref3 < indent.length)) {
+          if (indent === null || (0 < (_ref2 = attempt.length)) && (_ref2 < indent.length)) {
             indent = attempt;
           }
         }
@@ -452,7 +452,7 @@
       throw SyntaxError("Reserved word \"" + (this.value()) + "\" on line " + (this.line + 1) + " can't be assigned");
     };
     Lexer.prototype.balancedString = function(str, delimited, options) {
-      var _i, _len, _ref2, close, i, levels, open, pair, slen;
+      var _i, _len, close, i, levels, open, pair, slen;
       options || (options = {});
       levels = [];
       i = 0;
@@ -463,7 +463,7 @@
         } else {
           for (_i = 0, _len = delimited.length; _i < _len; _i++) {
             pair = delimited[_i];
-            _ref2 = pair, open = _ref2[0], close = _ref2[1];
+            open = pair[0], close = pair[1];
             if (levels.length && starts(str, close, i) && last(levels) === pair) {
               levels.pop();
               i += close.length - 1;

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";
+            join = i === this.properties.length - 1 ? '' : (prop === lastNoncom || prop instanceof Comment ? '\n' : ',\n');
-            if ((prop === lastNoncom) || (prop instanceof Comment)) {
-              join = "\n";
-            }
-            if (i === this.properties.length - 1) {
-              join = '';
-            }
             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');
+      valVar = value.compile(o);
-      assigns = [("" + 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) {
+        this.name = name.compile ? name : new Literal(name);
-          name = new Literal(name);
-        }
-        this.name = 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++) {
+        for (_j = 0, _len2 = (_ref3 = flatten([conditions])).length; _j < _len2; _j++) {
-          condition = _ref4[_j];
+          condition = _ref3[_j];
           if (this.tags.subjectless) {
             condition = new Op('!!', new Parens(condition));
           }

src/nodes.coffee

@@ -143,6 +143,9 @@ exports.Base = class Base
   isComplex       : YES
   topSensitive    : NO
 
+  # Is this node used to assign a certain variable?
+  assigns: NO
+
 #### Expressions
 
 # The expressions body is the list of expressions that forms the body of an
@@ -253,6 +256,8 @@ exports.Literal = class Literal extends Base
   isReserved: ->
     !!@value.reserved
 
+  assigns: (name) -> name is @value
+
   compileNode: (o) ->
     idt = if @isStatement(o) then @idt() else ''
     end = if @isStatement(o) then ';' else ''
@@ -324,6 +329,9 @@ exports.Value = class Value extends Base
   isComplex: ->
     @base.isComplex() or @hasProperties()
 
+  assigns: (name) ->
+    not @properties.length and @base.assigns name
+
   makeReturn: ->
     if @properties.length then super() else @base.makeReturn()
 
@@ -702,12 +710,15 @@ exports.ObjectLiteral = class ObjectLiteral extends Base
   compileNode: (o) ->
     top = del o, 'top'
     o.indent = @idt 1
-    nonComments = prop for prop in @properties when (prop not instanceof Comment)
+    nonComments = prop for prop in @properties when prop not instanceof Comment
-    lastNoncom  =  last nonComments
+    lastNoncom  = last nonComments
     props = for prop, i in @properties
-      join   = ",\n"
+      join = if i is @properties.length - 1
-      join   = "\n" if (prop is lastNoncom) or (prop instanceof Comment)
+        ''
-      join   = '' if i is @properties.length - 1
+      else if prop is lastNoncom or prop instanceof Comment
+        '\n'
+      else
+        ',\n'
       indent = if prop instanceof Comment then '' else @idt 1
       if prop instanceof Value and prop.tags.this
         prop = new Assign prop.properties[0].name, prop, 'object'
@@ -715,9 +726,13 @@ exports.ObjectLiteral = class ObjectLiteral extends Base
         prop = new Assign prop, prop, 'object'
       indent + prop.compile(o) + join
     props = props.join('')
-    obj   = '{' + (if props then '\n' + props + '\n' + @idt() else '') + '}'
+    obj   = "{#{ if props then '\n' + props + '\n' + @idt() else '' }}"
     if top then "(#{obj})" else obj
 
+  assigns: (name) ->
+    for prop in @properties when prop.assigns name then return yes
+    no
+
 #### ArrayLiteral
 
 # An array literal.
@@ -752,6 +767,10 @@ exports.ArrayLiteral = class ArrayLiteral extends Base
     else
       "[#{objects}]"
 
+  assigns: (name) ->
+    for obj in @objects when obj.assigns name then return yes
+    no
+
 #### Class
 
 # The CoffeeScript class definition.
@@ -898,16 +917,19 @@ exports.Assign = class Assign extends Base
       return new Assign(obj, value).compile o
     top     = del o, 'top'
     otop    = merge o, top: yes
-    valVar  = o.scope.freeVariable 'ref'
+    valVar  = value.compile o
-    assigns = ["#{valVar} = #{ value.compile o }"]
+    assigns = []
     splat   = false
+    if not IDENTIFIER.test(valVar) or @variable.assigns(valVar)
+      assigns.push "#{ ref = o.scope.freeVariable 'ref' } = #{valVar}"
+      valVar = ref
     for obj, i in objects
       # A regular array pattern-match.
       idx = i
       if isObject
         if obj instanceof Assign
           # A regular object pattern-match.
-          [obj, idx] = [obj.value, obj.variable.base]
+          {variable: {base: idx}, value: obj} = obj
         else
           # A shorthand `{a, b, @c} = val` pattern-match.
           idx = if obj.tags.this then obj.properties[0].name else obj
@@ -937,6 +959,9 @@ exports.Assign = class Assign extends Base
     val   = @value.compile(o)
     "([].splice.apply(#{name}, [#{from}, #{to}].concat(#{ref} = #{val})), #{ref})"
 
+  assigns: (name) ->
+    @[if @context is 'object' then 'value' else 'variable'].assigns name
+
 #### Code
 
 # A function definition. This is the only node that creates a new Scope.
@@ -1039,8 +1064,9 @@ exports.Splat = class Splat extends Base
 
   constructor: (name) ->
     super()
-    name = new Literal name unless name.compile
+    @name = if name.compile then name else new Literal name
-    @name = name
+
+  assigns: (name) -> @name.assigns name
 
   compileNode: (o) ->
     if @index? then @compileParam(o) else @name.compile(o)