Actually make computed readOnly:true. Add more tests.

src/lib/bind/accessors.html

@@ -174,8 +174,7 @@ subject to an additional IP rights grant found at http://polymer.github.io/PATEN
       // ReadOnly properties have a private setter only
       // TODO(kschaaf): Per current Bind factoring, we shouldn't
       // be interrogating the prototype here
-      var info = model.getPropertyInfo && model.getPropertyInfo(property);
-      if (info && (info.readOnly || info.computed)) {
+      if (model.getPropertyInfo && model.getPropertyInfo(property).readOnly) {
         model['_set' + this.upper(property)] = setter;
       } else {
         defun.set = setter;

src/standard/effectBuilder.html

@@ -55,6 +55,8 @@ subject to an additional IP rights grant found at http://polymer.github.io/PATEN
             this._addObserverEffect(p, prop.observer);
           }
           if (prop.computed) {
+            // Computed properties are implicitly readOnly
+            prop.readOnly = true;
             this._addComputedEffect(p, prop.computed);
           }
           if (prop.notify) {
@@ -63,7 +65,7 @@ subject to an additional IP rights grant found at http://polymer.github.io/PATEN
           if (prop.reflectToAttribute) {
             this._addPropertyEffect(p, 'reflect');
           }
-          if (prop.readOnly || prop.computed) {
+          if (prop.readOnly) {
             // Ensure accessor is created
             Polymer.Bind.ensurePropertyEffects(this, p);
           }

test/unit/bind-elements.html

@@ -248,6 +248,10 @@
       computedvalue="[[boundcomputedvalue]]"
       computednotifyingvalue="[[boundcomputednotifyingvalue]]">
     </x-basic>
+    <x-basic id="basic3"
+      notifyingvalue="{{computedValue}}"
+      computedvalue="{{value}}">
+    </x-basic>
   </template>
   <script>
     Polymer({
@@ -259,6 +263,17 @@
         'boundcomputednotifyingvalueChanged(boundcomputednotifyingvalue)',
         'boundreadonlyvalueChanged(boundreadonlyvalue)'
       ],
+      properties: {
+        a: {
+          value: 10
+        },
+        b: {
+          value: 20
+        },
+        computedValue: {
+          computed: 'computeComputedValue(a, b)'
+        }
+      },
       created: function() {
         this.observerCounts = {
           boundvalueChanged: 0,
@@ -268,6 +283,9 @@
           boundreadonlyvalueChanged: 0
         };
       },
+      computeComputedValue: function(a, b) {
+        return a + b;
+      },
       clearObserverCounts: function() {
         for (var i in this.observerCounts) {
           this.observerCounts[i] = 0;

test/unit/bind.html

@@ -94,7 +94,7 @@ suite('single-element binding effects', function() {
     assert.equal(el.$.boundChild.computedvalue, 45, 'Computed value not propagated to bound child');
   });
 
-  test('computed value readOnly from outside', function() {
+  test('computed value readOnly from imperative set', function() {
     el.value = 44;
     // Should have no effect
     el.computedvalue = 99;
@@ -303,6 +303,21 @@ suite('2-way binding effects between elements', function() {
     assert.equal(el.observerCounts.boundcomputedvalueChanged, 0, 'observer for property bound to non-notifying computed property called and should not have been');
   });
 
+  test('computed value readOnly from downward binding', function() {
+    el.$.basic3.value = 10;
+    assert.equal(el.$.basic3.computedvalue, 11);
+    // should have no effect
+    el.value = 99;
+    assert.equal(el.$.basic3.computedvalue, 11);
+  });
+
+  test('computed value readOnly from upward notification', function() {
+    assert.equal(el.computedValue, 30);
+    // should have no effect
+    el.$.basic3.notifyingvalue = 10;
+    assert.equal(el.computedValue, 30);
+  });
+
   test('binding to notifying property', function() {
     el.boundnotifyingvalue = 42;
     assert.equal(el.$.basic1.notifyingvalue, 42, 'binding to child not updated');