compiler: do not optimize Name

The optimization is wrong; they can't have side effects, but they can
raise errors.

Signed-off-by: Julien Danjou <julien@danjou.info>

hy/compiler.py

@@ -193,17 +193,13 @@ class Result(object):
         This is useful when we want to use the stored expression in a
         statement context (for instance in a code branch).
 
-        We drop bare names because they can't have any side effect, and they
-        make the generated code ugly.
-
         If there is no expression context, return an empty result.
         """
-        if self.expr and not isinstance(self.expr, ast.Name):
+        if self.expr:
             return Result() + ast.Expr(lineno=self.expr.lineno,
                                        col_offset=self.expr.col_offset,
                                        value=self.expr)
-        else:
-            return Result()
+        return Result()
 
     def rename(self, new_name):
         """Rename the Result's temporary variables to a `new_name`.

tests/native_tests/language.hy

@@ -640,3 +640,11 @@
   (setf f (quote (if true true true)))
   (assert (= (car f) "if"))
   (assert (= (cdr f) (quote (true true true)))))
+
+(defn test-undefined-name []
+  "NATIVE: test that undefined names raise errors"
+  (try
+   (do
+    xxx
+    (assert False))
+   (except [NameError])))