[pypy-commit] pypy default: (fijal, arigo)

[arigo]

Author: Armin Rigo <arigo at tunes.org>
Branch: 
Changeset: r53272:d8c92dd23635
Date: 2012-03-08 10:50 -0800
http://bitbucket.org/pypy/pypy/changeset/d8c92dd23635/

Log:	(fijal, arigo)

	Improve the error message in one annotation error case.

diff --git a/pypy/annotation/classdef.py b/pypy/annotation/classdef.py
--- a/pypy/annotation/classdef.py
+++ b/pypy/annotation/classdef.py
@@ -134,12 +134,19 @@
             if self.name not in homedef.classdesc.all_enforced_attrs:
                 self.attr_allowed = False
                 if not self.readonly:
-                    raise NoSuchAttrError(homedef, self.name)
+                    raise NoSuchAttrError(
+                        "setting forbidden attribute %r on %r" % (
+                        self.name, homedef))
 
     def modified(self, classdef='?'):
         self.readonly = False
         if not self.attr_allowed:
-            raise NoSuchAttrError(classdef, self.name)
+            raise NoSuchAttrError(
+                "Attribute %r on %r should be read-only.\n" % (self.name,
+                                                               classdef) +
+                "This error can be caused by another 'getattr' that promoted\n"
+                "the attribute here; the list of read locations is:\n" +
+                '\n'.join([str(loc[0]) for loc in self.read_locations]))
 
 
 class ClassDef(object):
diff --git a/pypy/annotation/test/test_annrpython.py b/pypy/annotation/test/test_annrpython.py
--- a/pypy/annotation/test/test_annrpython.py
+++ b/pypy/annotation/test/test_annrpython.py
@@ -2556,6 +2556,26 @@
         s = a.build_types(f, [int])
         assert s.knowntype == int
 
+    def test_slots_reads(self):
+        class A(object):
+            __slots__ = ()
+        class B(A):
+            def __init__(self, x):
+                self.x = x
+        def f(x):
+            if x:
+                a = A()
+            else:
+                a = B(x)
+            return a.x   # should explode here
+
+        a = self.RPythonAnnotator()
+        e = py.test.raises(Exception, a.build_types, f, [int])
+        # this should explode on reading the attribute 'a.x', but it can
+        # sometimes explode on 'self.x = x', which does not make much sense.
+        # But it looks hard to fix in general: we don't know yet during 'a.x'
+        # if the attribute x will be read-only or read-write.
+
     def test_unboxed_value(self):
         class A(object):
             __slots__ = ()