Fix list.pop(n) optimization for literal int argument.

Cython/Compiler/Optimize.py

@@ -2305,12 +2305,19 @@ class OptimizeBuiltinCalls(Visitor.EnvTransform):
                 utility_code = pop_utility_code
                 )
         elif len(args) == 2:
-            if isinstance(args[1], ExprNodes.CoerceToPyTypeNode) and args[1].arg.type.is_int:
-                original_type = args[1].arg.type
-                if PyrexTypes.widest_numeric_type(original_type, PyrexTypes.c_py_ssize_t_type) == PyrexTypes.c_py_ssize_t_type:
-                    args[1] = args[1].arg
+            index = args[1]
+            if isinstance(index, ExprNodes.CoerceToPyTypeNode):
+                index = index.arg
+            if isinstance(index, ExprNodes.IntNode):
+                index = index.coerce_to(PyrexTypes.c_py_ssize_t_type, None)
+            if index.type.is_int:
+                widest = PyrexTypes.widest_numeric_type(
+                    index.type, PyrexTypes.c_py_ssize_t_type)
+                if widest == PyrexTypes.c_py_ssize_t_type:
+                    args[1] = index
                     return ExprNodes.PythonCapiCallNode(
-                        node.pos, "__Pyx_PyObject_PopIndex", self.PyObject_PopIndex_func_type,
+                        node.pos, "__Pyx_PyObject_PopIndex",
+                        self.PyObject_PopIndex_func_type,
                         args = args,
                         may_return_none = True,
                         is_temp = node.is_temp,

tests/run/list_pop.pyx

@@ -125,6 +125,29 @@ def index_pop_typed(list L, int i):
     """
     return L.pop(i)
 
+@cython.test_assert_path_exists('//PythonCapiCallNode')
+@cython.test_fail_if_path_exists('//SimpleCallNode/AttributeNode')
+def index_pop_literal(list L):
+    """
+    >>> L = list(range(10))
+    >>> index_pop_literal(L)
+    0
+    >>> L
+    [1, 2, 3, 4, 5, 6, 7, 8, 9]
+
+    >>> while L:
+    ...    _ = index_pop_literal(L)
+
+    >>> L
+    []
+
+    >>> index_pop_literal(L)
+    Traceback (most recent call last):
+    ...
+    IndexError: pop from empty list
+    """
+    return L.pop(0)
+
 
 @cython.test_fail_if_path_exists('//PythonCapiCallNode')
 def crazy_pop(L):