Fix Py3 list comprehensions in (C-)class bodies: loop variable was declared in...

Fix Py3 list comprehensions in (C-)class bodies: loop variable was declared in the object struct instead of the scope that declared the class (usually the module init function).

CHANGES.rst

@@ -14,6 +14,9 @@ Features added
 Bugs fixed
 ----------
 
+* Py3 list comprehensions in class bodies resulted in invalid C code.
+  (Github issue #1889)
+
 * Modules built for later CPython 3.5.x versions failed to import in 3.5.1.
   (Github issue #1880)
 

Cython/Compiler/Symtab.py

@@ -1750,12 +1750,14 @@ class GeneratorExpressionScope(Scope):
     def __init__(self, outer_scope):
         name = outer_scope.global_scope().next_id(Naming.genexpr_id_ref)
         Scope.__init__(self, name, outer_scope, outer_scope)
-        self.var_entries = outer_scope.var_entries  # keep declarations outside
         self.directives = outer_scope.directives
         self.genexp_prefix = "%s%d%s" % (Naming.pyrex_prefix, len(name), name)
 
-        while outer_scope.is_genexpr_scope:
+        # Class/ExtType scopes are filled at class creation time, i.e. from the
+        # module init function or surrounding function.
+        while outer_scope.is_genexpr_scope or outer_scope.is_c_class_scope or outer_scope.is_py_class_scope:
             outer_scope = outer_scope.outer_scope
+        self.var_entries = outer_scope.var_entries  # keep declarations outside
         outer_scope.subscopes.add(self)
 
     def mangle(self, prefix, name):

tests/run/cython3.pyx

@@ -378,6 +378,24 @@ def list_comp_with_lambda():
     return result
 
 
+class ListCompInClass(object):
+    """
+    >>> x = ListCompInClass()
+    >>> x.listcomp
+    [1, 2, 3]
+    """
+    listcomp = [i+1 for i in range(3)]
+
+
+cdef class ListCompInCClass:
+    """
+    >>> x = ListCompInCClass()
+    >>> x.listcomp
+    [1, 2, 3]
+    """
+    listcomp = [i+1 for i in range(3)]
+
+
 module_level_lc = [ module_level_loopvar*2 for module_level_loopvar in range(4) ]
 def list_comp_module_level():
     """

tests/run/listcomp.pyx

@@ -84,6 +84,24 @@ def global_listcomp():
     """
 
 
+class ListCompInClass(object):
+    """
+    >>> x = ListCompInClass()
+    >>> x.listcomp
+    [1, 2, 3]
+    """
+    listcomp = [i+1 for i in range(3)]
+
+
+cdef class ListCompInCClass:
+    """
+    >>> x = ListCompInCClass()
+    >>> x.listcomp
+    [1, 2, 3]
+    """
+    listcomp = [i+1 for i in range(3)]
+
+
 def nested_result():
     """
     >>> nested_result()