Disallow nowhere.

src/api/loc.js

@@ -22,11 +22,20 @@ ol.loc = function(opt_arg){
         return opt_arg;
     }
     
-    var x = 0;
-    var y = 0;
+    /** @type {number|undefined} */
+    var x;
+
+    /** @type {number|undefined} */
+    var y;
+
+    /** @type {number|undefined} */
     var z;
+
+    /** @type {Object|undefined} */
     var projection;
     
+    var usage = 'ol.loc accepts a coordinate array or an object with x, y, and (optional) z properties';
+
     if (arguments.length == 1 && goog.isDef(opt_arg)) {
         if (goog.isArray(opt_arg)) {
             x = opt_arg[0];
@@ -39,10 +48,14 @@ ol.loc = function(opt_arg){
             z = opt_arg['z'];
             projection = opt_arg['projection'];
         } else {
-            throw new Error('ol.loc');
+            throw new Error(usage);
         }
     }
     
+    if (!goog.isNumber(x) || !goog.isNumber(y)) {
+        throw new Error(usage);
+    }
+
     if (goog.isDef(projection)) {
         projection = ol.projection(projection);
     }

test/spec/api/loc.test.js

@@ -1,11 +1,12 @@
 describe("ol.loc", function() {
 
-    it("allows empty construction", function() {
-        var loc;
+    it("doesn't allow empty construction", function() {
 
+        expect(function() {
             // nowhere
-        loc = ol.loc();
-        expect(loc).toBeA(ol.Loc);
+            var loc = ol.loc();
+        }).toThrow();
+
     });
         
     it("allows construction from an obj config", function() {