void/null now work as same as []/{} in LHS

Author: satyr

extras/coco.js

@@ -1,4 +1,4 @@
-var Node, Negatable, Lines, Literal, Key, Index, Value, Call, Clone, Obj, Arr, Op, Assign, Import, Of, Existence, Fun, Class, Super, Parens, Splat, Statement, Throw, Return, While, For, Try, Switch, Case, If, Comment, Util, SE, UTILITIES, LEVEL_TOP, LEVEL_PAREN, LEVEL_LIST, LEVEL_COND, LEVEL_OP, LEVEL_ACCESS, TAB, IDENTIFIER, _ref, __extends = function(sub, sup){
+var Node, Negatable, Lines, Literal, Key, Index, Value, Call, Clone, List, Obj, Arr, Op, Assign, Import, Of, Existence, Fun, Class, Super, Parens, Splat, Statement, Throw, Return, While, For, Try, Switch, Case, If, Comment, Util, SE, UTILITIES, LEVEL_TOP, LEVEL_PAREN, LEVEL_LIST, LEVEL_COND, LEVEL_OP, LEVEL_ACCESS, TAB, IDENTIFIER, _ref, __extends = function(sub, sup){
   function ctor(){} ctor.prototype = (sub.superclass = sup).prototype;
   return (sub.prototype = new ctor).constructor = sub;
 }, __importAll = function(obj, src){ for (var key in src) obj[key] = src[key]; return obj };
@@ -135,6 +135,7 @@ Node = (function(){
   _proto.isComplex = YES;
   _proto.isStatement = NO;
   _proto.isAssignable = NO;
+  _proto.isEmpty = NO;
   _proto.jumps = NO;
   _proto.assigns = NO;
   _proto.hasDefault = NO;
@@ -319,6 +320,13 @@ exports.Literal = Literal = (function(_super){
     return '"' + this.value + '"';
   };
   _proto.isComplex = NO;
+  _proto.isEmpty = function(){
+    switch (this.value) {
+    case 'void':
+    case 'null':
+      return true;
+    }
+  };
   _proto.isAssignable = function(){
     return IDENTIFIER.test(this.value);
   };
@@ -756,6 +764,15 @@ exports.Clone = Clone = (function(_super){
   };
   return Clone;
 }(Node));
+List = (function(_super){
+  var _proto = __extends(List, _super).prototype;
+  function List(){} List.name = 'List';
+  _proto.children = ['items'];
+  _proto.isEmpty = function(){
+    return !this.items.length;
+  };
+  return List;
+}(Node));
 exports.Obj = Obj = (function(_super){
   var _proto = __extends(Obj, _super).prototype;
   function _ctor(){} _ctor.prototype = _proto;
@@ -764,7 +781,6 @@ exports.Obj = Obj = (function(_super){
     _this.items = items || [];
     return _this;
   } Obj.name = 'Obj';
-  _proto.children = ['items'];
   _proto.assigns = function(it){
     var node, _i, _ref, _len;
     for (_i = 0, _len = (_ref = this.items).length; _i < _len; ++_i) {
@@ -829,7 +845,7 @@ exports.Obj = Obj = (function(_super){
     }
   };
   return Obj;
-}(Node));
+}(List));
 exports.Arr = Arr = (function(_super){
   var _proto = __extends(Arr, _super).prototype;
   function _ctor(){} _ctor.prototype = _proto;
@@ -863,7 +879,7 @@ exports.Arr = Arr = (function(_super){
     }
   };
   return Arr;
-}(Obj));
+}(List));
 exports.Op = Op = (function(_super){
   var EQUALITY, COMPARER, _proto = __extends(Op, _super).prototype;
   function _ctor(){} _ctor.prototype = _proto;
@@ -1045,7 +1061,11 @@ exports.Assign = Assign = (function(_super){
   };
   METHOD_DEF = /^(?:([\s\S]+)\.prototype(?=\.)|[\s\S]*?)(?:(?:\.|^)([$A-Za-z_\x7f-\uffff][$\w\x7f-\uffff]*)|\[(([\"\']).+?\4|\d+)])$/;
   _proto.compileNode = function(o){
-    var left, right, name, that, val, code;
+    var right, left, name, that, val, code;
+    right = this.right;
+    if (this.left.isEmpty()) {
+      return right.compile(o, LEVEL_ACCESS);
+    }
     left = this.transleft(o);
     if (left.items) {
       if (!this.logic) {
@@ -1056,7 +1076,6 @@ exports.Assign = Assign = (function(_super){
     if (this.logic) {
       return this.compileConditional(o, left);
     }
-    right = this.right;
     if (left.hasDefault()) {
       right = Op(left.op, right, left.second);
       left = left.first;
@@ -1102,9 +1121,7 @@ exports.Assign = Assign = (function(_super){
   _proto.compileDestructuring = function(o, left){
     var items, len, rite, rref, cache, list, code;
     items = left.items;
-    if (!(len = items.length)) {
-      return this.right.compile(o, LEVEL_ACCESS);
-    }
+    len = items.length;
     rite = this.right.compile(o, len === 1 ? LEVEL_ACCESS : LEVEL_LIST);
     if ((len > 1 || o.level) && (!IDENTIFIER.test(rite) || left.assigns(rite))) {
       cache = "" + (rref = o.scope.temporary('ref')) + " = " + rite;
@@ -1133,7 +1150,7 @@ exports.Assign = Assign = (function(_super){
     var i, node, len, val, ivar, start, inc, lr, _len, _results = [];
     for (i = 0, _len = nodes.length; i < _len; ++i) {
       node = nodes[i];
-      if (node.items && !node.items.length) {
+      if (node.isEmpty()) {
         continue;
       }
       if (node instanceof Splat) {
@@ -1465,7 +1482,9 @@ exports.Fun = Fun = (function(_super){
       } else if (arg instanceof Splat) {
         arg = arg.it;
       }
-      if (arg.isComplex()) {
+      if (arg.isEmpty()) {
+        arg = Literal(scope.temporary('arg'));
+      } else if (arg.isComplex()) {
         val = ref = paramName(o, p);
         if (dfv) {
           val = Op(p.op, ref, p.second);

lib/nodes.js

@@ -106,6 +106,7 @@ class Node
   isComplex    : YES
   isStatement  : NO
   isAssignable : NO
+  isEmpty      : NO
   # Do I contain a statement that jumps out of me?
   jumps: NO
   # Do I assign a certain variable?
@@ -225,6 +226,9 @@ class exports.Literal extends Node
 
   isComplex: NO
 
+  isEmpty: ->
+    switch @value case <[ void null ]> then return true
+
   isAssignable : -> IDENTIFIER.test @value
   assigns      : -> it is @value
 
@@ -487,13 +491,17 @@ class exports.Clone extends Node
     call = Parens call, true if @newed
     Import(call, @mixin).compileNode o
 
+#### List
+# An abstract node for a list of items.
+class List extends Node
+  children : [\items]
+  isEmpty  : -> not @items.length
+
 #### Obj
 # `{x: y}`
-class exports.Obj extends Node
+class exports.Obj extends List
   (@items or []) =>
 
-  children: [\items]
-
   assigns: -> return true if node.assigns it for node of @items
 
   compileNode: (o) ->
@@ -530,7 +538,7 @@ class exports.Obj extends Node
 
 #### Arr
 # `[x, y]`
-class exports.Arr extends Obj
+class exports.Arr extends List
   (@items or []) =>
 
   compileNode: (o) ->
@@ -665,12 +673,13 @@ class exports.Assign extends Node
   $ ///
 
   compileNode: (o) ->
+    {right} = this
+    return right.compile o, LEVEL_ACCESS if @left.isEmpty()
     left = @transleft o
     if left.items
       return @compileDestructuring o, left unless @logic
       throw SE "\"#{@show()}\" cannot destructure"
     return @compileConditional o, left if @logic
-    {right} = this
     if left.hasDefault()
       right = Op left.op, right, left.second
       left.=first
@@ -703,8 +712,7 @@ class exports.Assign extends Node
   # when assigning to an array or object literal.
   # See <http://wiki.ecmascript.org/doku.php?id=harmony:destructuring>.
   compileDestructuring: (o, left) ->
-    {items} = left
-    return @right.compile o, LEVEL_ACCESS unless len = items.length
+    {items} = left; len = items.length
     rite = @right.compile o, if len is 1 then LEVEL_ACCESS else LEVEL_LIST
     if (len > 1 or o.level) and
        (not IDENTIFIER.test(rite) or left.assigns(rite))
@@ -721,7 +729,7 @@ class exports.Assign extends Node
 
   destructArr: (o, nodes, rite) ->
     for node, i of nodes
-      continue if node.items and not node.items.length
+      continue if node.isEmpty()
       if node instanceof Splat
         throw SE 'multiple splats in an assignment' if ivar
         len = nodes.length
@@ -928,7 +936,9 @@ class exports.Fun extends Node
       arg = p
       if dfv = arg.hasDefault()    then arg.=first
       else if arg instanceof Splat then arg.=it
-      if arg.isComplex()
+      if arg.isEmpty()
+        arg = Literal scope.temporary \arg
+      else if arg.isComplex()
         val = ref = paramName o, p
         val = Op p.op, ref, p.second if dfv
         asns.push Assign arg, val

src/nodes.co

@@ -233,3 +233,7 @@ new ->
 
   @{a ? 2, \b ? 3, ([\c]) ? 5} = {}
   eq @a * @b * @c, 30
+
+
+[void, null, v] = [1 to 3]
+eq v, 3