# HG changeset patch
# User Paul Boddie <paul@boddie.org.uk>
# Date 1531150355 -7200
# Node ID 9adc6e8a6fed51a7707e4b5e63da977811ca2a5c
# Parent  ea1e1157afc4bea57e7ce3305e837746db651d54
Introduced restrictions on privileged attributes, allowing internal access only.

diff -r ea1e1157afc4 -r 9adc6e8a6fed common.py
--- a/common.py	Thu Jul 05 23:41:16 2018 +0200
+++ b/common.py	Mon Jul 09 17:32:35 2018 +0200
@@ -462,7 +462,9 @@
         for i, node in enumerate(n.nodes):
             statements.append(
                 compiler.ast.Assign([node], compiler.ast.CallFunc(
-                    compiler.ast.Getattr(compiler.ast.Name(temp), "__get_single_item_unchecked__"),
+                    compiler.ast.Getattr(compiler.ast.Name(temp),
+                                         "__get_single_item_unchecked__",
+                                         privileged=True),
                     [compiler.ast.Const(i, str(i))]))
                 )
 
@@ -1591,6 +1593,10 @@
 
 predefined_constants = "False", "None", "NotImplemented", "True"
 
+privileged_attributes = [
+    "__get_single_item_unchecked__",
+    ]
+
 unary_operator_functions = {
 
     # Unary operations.
diff -r ea1e1157afc4 -r 9adc6e8a6fed compiler/ast.py
--- a/compiler/ast.py	Thu Jul 05 23:41:16 2018 +0200
+++ b/compiler/ast.py	Mon Jul 09 17:32:35 2018 +0200
@@ -868,11 +868,15 @@
         return "%s %s" % (self.expr, " ".join(map(str, self.quals)))
 
 class Getattr(Node):
-    def __init__(self, expr, attrname, lineno=None):
+    def __init__(self, expr, attrname, lineno=None, privileged=False):
         self.expr = expr
         self.attrname = attrname
         self.lineno = lineno
 
+        # Support privileged internal accesses.
+
+        self.privileged = privileged
+
     def getChildren(self):
         return self.expr, self.attrname
 
diff -r ea1e1157afc4 -r 9adc6e8a6fed inspector.py
--- a/inspector.py	Thu Jul 05 23:41:16 2018 +0200
+++ b/inspector.py	Mon Jul 09 17:32:35 2018 +0200
@@ -21,7 +21,8 @@
 """
 
 from branching import BranchTracker
-from common import CommonModule, get_argnames, init_item, predefined_constants
+from common import CommonModule, get_argnames, init_item, \
+                   predefined_constants, privileged_attributes
 from modules import BasicModule, CacheWritingModule, InspectionNaming
 from errors import InspectError
 from referencing import Reference
@@ -358,6 +359,16 @@
 
         "Process the given attribute access node 'n'."
 
+        path = self.get_namespace_path()
+
+        # Test for access to special privileged attributes.
+
+        if isinstance(n, compiler.ast.Getattr) and \
+           n.attrname in privileged_attributes and not n.privileged:
+
+            raise InspectError("Attribute %s is accessed by an unprivileged operation." %
+                               n.attrname, path, n)
+
         # Obtain any completed chain and return the reference to it.
 
         name_ref = self.process_attribute_chain(n)
@@ -372,8 +383,6 @@
         # either being name-based and thus an access rooted on a name, or being
         # based on some other node and thus an anonymous access of some kind.
 
-        path = self.get_namespace_path()
-
         # Start with the the full attribute chain.
 
         remaining = self.attrs
diff -r ea1e1157afc4 -r 9adc6e8a6fed tests/tuple_unpack_bad.py
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/tests/tuple_unpack_bad.py	Mon Jul 09 17:32:35 2018 +0200
@@ -0,0 +1,9 @@
+def good(t):
+    a, b, c = t
+
+def bad(t):
+    a = t.__get_single_item_unchecked__(0)
+
+t = 1, 2, 3
+good(t)
+bad(t)