From 03aafad65719d147a39cbc948020aa03b5daa94d Mon Sep 17 00:00:00 2001
From: Kodi Arfer <git@arfer.net>
Date: Tue, 24 Jul 2018 08:59:52 -0700
Subject: [PATCH] Make empty expressions illegal at the top level

---
 NEWS.rst                       | 7 +++++++
 hy/compiler.py                 | 5 +++--
 tests/compilers/test_ast.py    | 6 ++++++
 tests/native_tests/language.hy | 5 -----
 4 files changed, 16 insertions(+), 7 deletions(-)

diff --git a/NEWS.rst b/NEWS.rst
index 3b57b8a..2b92b99 100644
--- a/NEWS.rst
+++ b/NEWS.rst
@@ -1,5 +1,12 @@
 .. default-role:: code
 
+Unreleased
+==============================
+
+Removals
+------------------------------
+* Empty expressions (`()`) are no longer legal at the top level.
+
 0.15.0
 ==============================
 
diff --git a/hy/compiler.py b/hy/compiler.py
index 8fcb854..f92fe4d 100755
--- a/hy/compiler.py
+++ b/hy/compiler.py
@@ -1546,8 +1546,9 @@ class HyASTCompiler(object):
             # Go through compile again if the type changed.
             return self.compile(expression)
 
-        if expression == []:
-            return self.compile_atom(HyList().replace(expression))
+        if not expression:
+            raise HyTypeError(
+                expression, "empty expressions are not allowed at top level")
 
         fn = expression[0]
         func = None
diff --git a/tests/compilers/test_ast.py b/tests/compilers/test_ast.py
index 5fbc727..a5f42af 100644
--- a/tests/compilers/test_ast.py
+++ b/tests/compilers/test_ast.py
@@ -67,6 +67,12 @@ def test_ast_bad_type():
         pass
 
 
+def test_empty_expr():
+    "Empty expressions should be illegal at the top level."
+    cant_compile("(print ())")
+    can_compile("(print '())")
+
+
 def test_ast_bad_if():
     "Make sure AST can't compile invalid if*"
     cant_compile("(if*)")
diff --git a/tests/native_tests/language.hy b/tests/native_tests/language.hy
index 37f4d4d..59141b5 100644
--- a/tests/native_tests/language.hy
+++ b/tests/native_tests/language.hy
@@ -1401,11 +1401,6 @@
   (assert (= y [5])))
 
 
-(defn test-empty-list []
-  "Evaluate an empty list to a []"
-  (assert (= () [])))
-
-
 (defn test-string []
   (assert (string? (string "a")))
   (assert (string? (string 1)))