Enchancing pattern matching with @vars ... issue #721

lib/grammar.js

@@ -88,7 +88,7 @@
     AssignObj: [
       o("Identifier", function() {
         return new ValueNode($1);
-      }), o("AlphaNumeric"), o("Identifier : Expression", function() {
+      }), o("AlphaNumeric"), o("ThisProperty"), o("Identifier : Expression", function() {
         return new AssignNode(new ValueNode($1), $3, 'object');
       }), o("AlphaNumeric : Expression", function() {
         return new AssignNode(new ValueNode($1), $3, 'object');
@@ -309,7 +309,7 @@
     ],
     ThisProperty: [
       o("@ Identifier", function() {
-        return new ValueNode(new LiteralNode('this'), [new AccessorNode($2)]);
+        return new ValueNode(new LiteralNode('this'), [new AccessorNode($2)], 'this');
       })
     ],
     Range: [

lib/nodes.js

@@ -300,11 +300,14 @@
     return ReturnNode;
   })();
   exports.ValueNode = (function() {
-    ValueNode = function(_arg, _arg2) {
+    ValueNode = function(_arg, _arg2, tag) {
       this.properties = _arg2;
       this.base = _arg;
       ValueNode.__super__.constructor.call(this);
       this.properties || (this.properties = []);
+      if (tag) {
+        this.tags[tag] = true;
+      }
       return this;
     };
     __extends(ValueNode, BaseNode);
@@ -798,7 +801,9 @@
               join = '';
             }
             indent = prop instanceof CommentNode ? '' : this.idt(1);
-            if (!(prop instanceof AssignNode || prop instanceof CommentNode)) {
+            if (prop instanceof ValueNode && prop.tags['this']) {
+              prop = new AssignNode(prop.properties[0].name, prop, 'object');
+            } else if (!(prop instanceof AssignNode) && !(prop instanceof CommentNode)) {
               prop = new AssignNode(prop, prop, 'object');
             }
             return indent + prop.compile(o) + join;
@@ -1018,7 +1023,11 @@
           if (obj instanceof AssignNode) {
             _ref2 = [obj.value, obj.variable.base], obj = _ref2[0], idx = _ref2[1];
           } else {
-            idx = obj;
+            if (obj.tags['this']) {
+              idx = obj.properties[0].name;
+            } else {
+              idx = obj;
+            }
           }
         }
         if (!(obj instanceof ValueNode || obj instanceof SplatNode)) {

src/grammar.coffee

@@ -149,6 +149,7 @@ grammar =
   AssignObj: [
     o "Identifier",                             -> new ValueNode $1
     o "AlphaNumeric"
+    o "ThisProperty"
     o "Identifier : Expression",                -> new AssignNode new ValueNode($1), $3, 'object'
     o "AlphaNumeric : Expression",              -> new AssignNode new ValueNode($1), $3, 'object'
     o "Identifier : INDENT Expression OUTDENT", -> new AssignNode new ValueNode($1), $4, 'object'
@@ -340,7 +341,7 @@ grammar =
 
   # A reference to a property on *this*.
   ThisProperty: [
-    o "@ Identifier",                           -> new ValueNode new LiteralNode('this'), [new AccessorNode($2)]
+    o "@ Identifier",                           -> new ValueNode new LiteralNode('this'), [new AccessorNode($2)], 'this'
   ]
 
   # The CoffeeScript range literal.

src/nodes.coffee

@@ -294,9 +294,10 @@ exports.ValueNode = class ValueNode extends BaseNode
   children: ['base', 'properties']
 
   # A **ValueNode** has a base and a list of property accesses.
-  constructor: (@base, @properties) ->
+  constructor: (@base, @properties, tag) ->
     super()
     @properties or= []
+    @tags[tag] = yes if tag
 
   # Add a property access to the list.
   push: (prop) ->
@@ -713,7 +714,10 @@ exports.ObjectNode = class ObjectNode extends BaseNode
       join   = "\n" if (prop is lastNoncom) or (prop instanceof CommentNode)
       join   = '' if i is @properties.length - 1
       indent = if prop instanceof CommentNode then '' else @idt 1
-      prop   = new AssignNode prop, prop, 'object' unless prop instanceof AssignNode or prop instanceof CommentNode
+      if prop instanceof ValueNode and prop.tags['this']
+        prop = new AssignNode prop.properties[0].name, prop, 'object'
+      else if prop not instanceof AssignNode and prop not instanceof CommentNode
+        prop = new AssignNode prop, prop, 'object'
       indent + prop.compile(o) + join
     props = props.join('')
     obj   = '{' + (if props then '\n' + props + '\n' + @idt() else '') + '}'
@@ -900,8 +904,12 @@ exports.AssignNode = class AssignNode extends BaseNode
           # A regular object pattern-match.
           [obj, idx] = [obj.value, obj.variable.base]
         else
-          # A shorthand `{a, b, c} = val` pattern-match.
-          idx = obj
+          if obj.tags['this']
+            # A shorthand `{@a, @b, @c} = val` pattern-match.
+            idx = obj.properties[0].name
+          else
+            # A shorthand `{a, b, c} = val` pattern-match.
+            idx = obj
       unless obj instanceof ValueNode or obj instanceof SplatNode
         throw new Error 'pattern matching must use only identifiers on the left-hand side.'
       accessClass = if isObject and IDENTIFIER.test(idx.value) then AccessorNode else IndexNode

test/test_literals.coffee

@@ -249,3 +249,14 @@ ok b is 100
 eq '\\`', `
   "\\\`"
 `
+
+
+# Shorthand objects with property references.
+obj =
+  one: 1
+  two: 2
+  func: -> {@one, @two}
+
+result = obj.func()
+ok result.one is 1
+ok result.two is 2

test/test_pattern_matching.coffee

@@ -142,3 +142,17 @@ ok a is 101
 
 [x] = {0: y} = {'0': z} = [Math.random()]
 ok x is y is z, 'destructuring in multiple'
+
+
+# Destructuring into an object.
+obj =
+  func: (list, object) ->
+    [@one, @two] = list
+    {@a, @b} = object
+
+obj.func [1, 2], a: 'a', b: 'b'
+
+eq obj.one, 1
+eq obj.two, 2
+eq obj.a, 'a'
+eq obj.b, 'b'