computed properties

lib/ast.js

@@ -921,6 +921,16 @@ var AST_ObjectKeyVal = DEFNODE("ObjectKeyVal", "quote", {
     }
 }, AST_ObjectProperty);
 
+var AST_ObjectComputedKeyVal = DEFNODE("ObjectComputedKeyVal", null, {
+    $documentation: "An object property whose key is computed. Like `[Symbol.iterator]: function...` or `[routes.homepage]: renderHomepage`",
+    _walk: function(visitor) {
+        return visitor._visit(this, function(){
+            this.key._walk(visitor);
+            this.value._walk(visitor);
+        });
+    }
+}, AST_ObjectProperty);
+
 var AST_ObjectSymbol = DEFNODE("ObjectSymbol", "symbol", {
     $propdoc: {
         symbol: "[AST_SymbolRef] what symbol it is"

lib/compress.js

@@ -952,6 +952,9 @@ merge(Compressor.prototype, {
             return false;
         });
         def(AST_ObjectProperty, function(compressor){
+            if (this instanceof AST_ObjectComputedKeyVal &&
+                    this.key.has_side_effects(compressor))
+                return true;
             return this.value.has_side_effects(compressor);
         });
         def(AST_Array, function(compressor){

lib/output.js

@@ -1203,6 +1203,13 @@ function OutputStream(options) {
         self.key.print(output);
         self.value._do_print(output, true);
     });
+    DEFPRINT(AST_ObjectComputedKeyVal, function(self, output) {
+        output.print("[");
+        self.key.print(output);
+        output.print("]:");
+        output.space();
+        self.value.print(output);
+    });
     DEFPRINT(AST_Symbol, function(self, output){
         var def = self.definition();
         output.print_name(def ? def.mangled_name || def.name : self.name);

lib/parse.js

@@ -1466,6 +1466,15 @@ function parse($TEXT, options) {
                 }
             }
 
+            if (type == "punc" && start.value == "[") {
+                expect(":");
+                a.push(new AST_ObjectComputedKeyVal({
+                    key: name,
+                    value: expression(false)
+                }));
+                continue;
+            }
+            
             if (!is("punc", ":")) {
                 // It's one of those object destructurings, the value is its own name
                 a.push(new AST_ObjectSymbol({
@@ -1495,6 +1504,12 @@ function parse($TEXT, options) {
         var tmp = S.token;
         next();
         switch (tmp.type) {
+          case "punc":
+            if (tmp.value === "[") {
+                var ex = expression(false);
+                expect("]");
+                return ex;
+            } else unexpected();
           case "num":
           case "string":
           case "name":

test/compress/harmony.js

@@ -36,6 +36,13 @@ regression_arrow_functions_and_hoist: {
     expect_exact: "a=>b;"
 }
 
+computed_property_names: {
+    input: {
+        obj({ ["x" + "x"]: 6 });
+    }
+    expect_exact: "obj({[\"x\"+\"x\"]:6});"
+}
+
 typeof_arrow_functions: {
     options = {
         evaluate: true