Be less clever about eliminating side-effect-free statements.

Closes #17.

lib/emit.js

@@ -325,8 +325,12 @@ Ep.explodeStatement = function(path, labelId) {
   }
 
   if (!meta.containsLeap(stmt)) {
-    if (meta.hasSideEffects(stmt))
-      self.emit(stmt);
+    // Technically we should be able to avoid emitting the statement
+    // altogether if !meta.hasSideEffects(stmt), but that leads to
+    // confusing generated code (for instance, `while (true) {}` just
+    // disappears) and is probably a more appropriate job for a dedicated
+    // dead code elimination pass.
+    self.emit(stmt);
     return;
   }
 

test/tests.es6.js

@@ -739,3 +739,24 @@ describe("catch parameter shadowing", function() {
     check(gen(11), [11, 13, 26, 5, 4, 11]);
   });
 });
+
+describe("empty while loops", function() {
+  it("should be preserved in generated code", function() {
+    function *gen(x) {
+      while (x) {
+        // empty while loop
+      }
+
+      do {
+        // empty do-while loop
+      } while (x);
+
+      return gen.toString();
+    }
+
+    var info = gen(false).next();
+    assert.strictEqual(info.done, true);
+    assert.ok(/empty while loop/.test(info.value));
+    assert.ok(/empty do-while loop/.test(info.value));
+  });
+});