fix predence of destructuring parameters - fixes #2269

packages/babel-core/src/transformation/transformers/es6/destructuring.js

@@ -95,7 +95,7 @@ export var visitor = {
       t.inherits(ref, pattern);
 
       var destructuring = new DestructuringTransformer({
-        blockHoist: node.params.length - i,
+        blockHoist: node.params.length - i + 1,
         nodes:      nodes,
         scope:      scope,
         file:       file,

packages/babel-core/test/fixtures/transformation/es6.destructuring/default-precedence/exec.js

@@ -0,0 +1,8 @@
+const f0 = (a, b = a, c = b) => [a, b, c];
+assert.deepEqual(f0(1), [1, 1, 1]);
+
+const f1 = ({a}, b = a, c = b) => [a, b, c];
+assert.deepEqual(f1({a: 1}), [1, 1, 1]);
+
+const f2 = ({a}, b = a, c = a) => [a, b, c];
+assert.deepEqual(f2({a: 1}), [1, 1, 1]);