Merge pull request #617 from rwtolbert/bugfix/assign_to_None

Adding code to prevent assignment to some core builtin names

hy/compiler.py

@@ -47,6 +47,7 @@ import importlib
 import codecs
 import ast
 import sys
+import keyword
 
 from collections import defaultdict
 
@@ -73,6 +74,21 @@ def load_stdlib():
             _stdlib[e] = module
 
 
+# True, False and None included here since they
+# are assignable in Python 2.* but become
+# keywords in Python 3.*
+def _is_hy_builtin(name, module_name):
+    extras = ['True', 'False', 'None',
+              'true', 'false', 'nil', 'null']
+    if name in extras or keyword.iskeyword(name):
+        return True
+    # for non-Hy modules, check for pre-existing name in
+    # _compile_table
+    if not module_name.startswith("hy."):
+        return name in _compile_table
+    return False
+
+
 _compile_table = {}
 
 
@@ -1751,6 +1767,12 @@ class HyASTCompiler(object):
 
     def _compile_assign(self, name, result,
                         start_line, start_column):
+
+        str_name = "%s" % name
+        if _is_hy_builtin(str_name, self.module_name):
+            raise HyTypeError(name,
+                              "Can't assign to a builtin: `%s'" % str_name)
+
         result = self.compile(result)
         ld_name = self.compile(name)
 

tests/native_tests/language.hy

@@ -28,6 +28,28 @@
   (setv (get foo 0) 12)
   (assert (= (get foo 0) 12)))
 
+(defn test-setv-builtin []
+  "NATIVE: test that setv doesn't work on builtins"
+  (try (eval '(setv False 1))
+       (catch [e [TypeError]] (assert (in "Can't assign to a builtin" (str e)))))
+  (try (eval '(setv True 0))
+       (catch [e [TypeError]] (assert (in "Can't assign to a builtin" (str e)))))
+  (try (eval '(setv None 1))
+       (catch [e [TypeError]] (assert (in "Can't assign to a builtin" (str e)))))
+  (try (eval '(setv false 1))
+       (catch [e [TypeError]] (assert (in "Can't assign to a builtin" (str e)))))
+  (try (eval '(setv true 0))
+       (catch [e [TypeError]] (assert (in "Can't assign to a builtin" (str e)))))
+  (try (eval '(setv nil 1))
+       (catch [e [TypeError]] (assert (in "Can't assign to a builtin" (str e)))))
+  (try (eval '(setv null 1))
+       (catch [e [TypeError]] (assert (in "Can't assign to a builtin" (str e)))))
+  (try (eval '(defn defclass [] (print "hello")))
+       (catch [e [TypeError]] (assert (in "Can't assign to a builtin" (str e)))))
+  (try (eval '(defn get [] (print "hello")))
+       (catch [e [TypeError]] (assert (in "Can't assign to a builtin" (str e)))))
+  (try (eval '(defn lambda [] (print "hello")))
+       (catch [e [TypeError]] (assert (in "Can't assign to a builtin" (str e))))))
 
 (defn test-for-loop []
   "NATIVE: test for loops"