More informative load errors

.gitignore

@@ -3,3 +3,4 @@ bower_components
 tmp
 coverage
 .DS_Store
+*.sw?

src/loader.js

@@ -516,14 +516,35 @@ function logloads(loads) {
 
   // 15.2.5.2.4
   function linkSetFailed(linkSet, load, exc) {
+    function requestsForLoad() {
+      var reqs = [];
+      linkSet.loads.forEach(function(aLoad){
+        aLoad.dependencies.forEach(function(dep){
+          if (dep.value == load.name) {
+            reqs.push({as: dep.key, from: aLoad.name});
+          }
+        });
+      });
+      return reqs;
+    }
+
     var loader = linkSet.loader;
+    var requests;
 
     if (load) {
-      if (load && linkSet.loads[0].name != load.name)
-        exc = addToError(exc, 'Error loading ' + load.name + ' from ' + linkSet.loads[0].name);
-
-      if (load)
+      if (linkSet.loads[0].name != load.name) {
+        requests = requestsForLoad();
+
+        if (requests[0]) {
+          var req = requests[0];
+          exc = addToError(exc, 'Error loading ' + load.name + ' as "' + req.as + '" from ' + req.from);
+        } else {
+          exc = addToError(exc, 'Error loading ' + load.name + ' from ' + linkSet.loads[0].name);
+        }
+      }
+      else {
         exc = addToError(exc, 'Error loading ' + load.name);
+      }
     }
     else {
       exc = addToError(exc, 'Error linking ' + linkSet.loads[0].name);

src/system-fetch.js

@@ -33,7 +33,7 @@
         fulfill(xhr.responseText);
       }
       function error() {
-        reject(xhr.statusText + ': ' + url || 'XHR error');
+        reject(new Error(xhr.statusText + ': ' + url || 'XHR error'));
       }
 
       xhr.onreadystatechange = function () {
@@ -68,9 +68,9 @@
       else
         url = url.substr(7);
       return fs.readFile(url, function(err, data) {
-        if (err)
+        if (err) {
           return reject(err);
-        else {
+        } else {
           // Strip Byte Order Mark out if it's the leading char
           var dataString = data + '';
           if (dataString[0] === '\ufeff')
@@ -89,4 +89,4 @@
     return new Promise(function(resolve, reject) {
       fetchTextFromURL(load.address, resolve, reject);
     });
-  };
+  };

test/loads/indirect-load.js

@@ -0,0 +1 @@
+import './load-non-existent.js';

test/loads/noent.js

@@ -0,0 +1 @@
+export { nothing } from 'nosuchfile.js';