From 87acb738412d1462ec7192b5fb33f6ffc4e84cd0 Mon Sep 17 00:00:00 2001
From: Josselin <josselin@trailofbits.com>
Date: Mon, 22 Oct 2018 19:01:55 +0100
Subject: [PATCH] SlithIR: add points_to property to ReferenceVariable

---
 slither/slithir/convert.py             | 11 +++++++++++
 slither/slithir/variables/reference.py | 24 +++++++++++++++++++++++-
 2 files changed, 34 insertions(+), 1 deletion(-)

diff --git a/slither/slithir/convert.py b/slither/slithir/convert.py
index da72b560e..03834b84c 100644
--- a/slither/slithir/convert.py
+++ b/slither/slithir/convert.py
@@ -511,10 +511,21 @@ def apply_ir_heuristics(irs, node):
 #    irs = replace_calls(irs)
     irs = remove_unused(irs)
 
+    find_references_origin(irs)
+
     reset_variable_number(irs)
 
     return irs
 
+def find_references_origin(irs):
+    """
+        Make lvalue of each Index, Member operation
+        points to the left variable
+    """
+    for ir in irs:
+        if isinstance(ir, (Index, Member)):
+            ir.lvalue.points_to = ir.variable_left
+
 def reset_variable_number(result):
     """
         Reset the number associated to slithIR variables
diff --git a/slither/slithir/variables/reference.py b/slither/slithir/variables/reference.py
index 18f33733e..bd93f9f1f 100644
--- a/slither/slithir/variables/reference.py
+++ b/slither/slithir/variables/reference.py
@@ -1,6 +1,8 @@
 
-from slither.core.variables.variable import Variable
 from slither.core.children.child_node import ChildNode
+from slither.core.declarations import Contract, Enum, SolidityVariableComposed
+from slither.core.variables.variable import Variable
+
 
 class ReferenceVariable(ChildNode, Variable):
 
@@ -10,6 +12,7 @@ class ReferenceVariable(ChildNode, Variable):
         super(ReferenceVariable, self).__init__()
         self._index = ReferenceVariable.COUNTER
         ReferenceVariable.COUNTER += 1
+        self._points_to = None
 
     @property
     def index(self):
@@ -19,6 +22,25 @@ class ReferenceVariable(ChildNode, Variable):
     def index(self, idx):
         self._index = idx
 
+    @property
+    def points_to(self):
+        """
+            Return the variable pointer by the reference
+            It is the left member of a Index or Member operator
+        """
+        return self._points_to
+
+    @points_to.setter
+    def points_to(self, points_to):
+        # Can only be a rvalue of
+        # Member or Index operator
+        from slither.slithir.utils.utils import is_valid_lvalue
+        assert is_valid_lvalue(points_to) \
+            or points_to == SolidityVariableComposed('msg.data') \
+            or isinstance(points_to, (Contract, Enum))
+
+        self._points_to = points_to
+
     @property
     def name(self):
         return 'REF_{}'.format(self.index)