Detect situation where functions are called as methods

Fix #2156

pythran/tests/test_normalize_methods.py

@@ -1,3 +1,4 @@
+import pythran
 from pythran.tests import TestEnv
 
 import numpy
@@ -124,6 +125,16 @@ def test_dispatch_update(self):
                       {1}, {1:1},
                       dispatch_update=[Set[int], Dict[int,int]])
 
+    def test_invalid_method_call(self):
+        code = '''
+def np_asarray7(sRate=44100):
+    import numpy as np
+    x = np.expand_dims(np.ones(sRate),-1)
+    x = np.maximum(np.minimum(x,.5),-.5).asarray()  # asarray is not a method
+    return x'''
+        with self.assertRaises(pythran.syntax.PythranSyntaxError):
+                self.run_test(code, 30, np_asarray7=[int])
+
     def test_capture_bound_method(self):
         code = '''
 def capture_bound_method(fname, r):

pythran/transformations/normalize_method_calls.py

@@ -27,7 +27,8 @@ class NormalizeMethodCalls(Transformation):
 
     def __init__(self):
         Transformation.__init__(self, Globals, Ancestors)
-        self.imports = {'builtins': 'builtins'}
+        self.imports = {'builtins': 'builtins',
+                        mangle('__dispatch__'): '__dispatch__'}
         self.to_import = set()
 
     def visit_Module(self, node):
@@ -156,6 +157,7 @@ def visit_Attribute(self, node):
                 self.update = True
                 mod = methods[node.attr][0]
                 self.to_import.add(mangle(mod[0]))
+                self.to_import.add(mangle('functools'))
                 func = self.attr_to_func(node)
                 z = ast.Call(
                     ast.Attribute(
@@ -250,7 +252,16 @@ def visit_Call(self, node):
                     self.to_import.add(mangle(mod[0]))
                     node.func = self.attr_to_func(node.func)
                 # else methods have been called using function syntax
-            if node.func.attr in methods or node.func.attr in functions:
+
+            ismethod = node.func.attr in methods
+            isfunction = node.func.attr in functions
+            if ismethod or isfunction:  # i.e. if it's callable
+                if not ismethod and self.baseobj(node.func.value):
+                    raise PythranSyntaxError(
+                            "'{}' called as a method while it's a function"
+                            .format(node.func.attr),
+                            node)
+
                 # Now, methods and function have both function syntax
                 def rec(path, cur_module):
                     """