Fix incorrect handling of nested return values

slither/slithir/operations/call.py

@@ -15,12 +15,3 @@ class Call(Operation):
     def arguments(self, v):
         self._arguments = v
 
-    # if array inside the parameters
-    def _unroll(self, l):
-        ret = []
-        for x in l:
-            if not isinstance(x, list):
-                ret += [x]
-            else:
-                ret += self._unroll(x)
-        return ret

slither/slithir/operations/init_array.py

@@ -21,16 +21,6 @@ class InitArray(OperationWithLValue):
         self._init_values = init_values
         self._lvalue = lvalue
 
-    # if array inside the init values
-    def _unroll(self, l):
-        ret = []
-        for x in l:
-            if not isinstance(x, list):
-                ret += [x]
-            else:
-                ret += self._unroll(x)
-        return ret
-
     @property
     def read(self):
         return self._unroll(self.init_values)

slither/slithir/operations/operation.py

@@ -29,3 +29,12 @@ class Operation(Context, ChildNode, AbstractOperation):
         """
         return self.read
 
+    # if array inside the parameters
+    def _unroll(self, l):
+        ret = []
+        for x in l:
+            if not isinstance(x, list):
+                ret += [x]
+            else:
+                ret += self._unroll(x)
+        return ret

slither/slithir/operations/return_operation.py

@@ -18,14 +18,20 @@ class Return(Operation):
             else:
                 values = [values]
         else:
-            for value in values:
-                assert is_valid_rvalue(value) or isinstance(value, TupleVariable)
+            self._valid_value(values)
         super(Return, self).__init__()
         self._values = values
 
+    def _valid_value(self, value):
+        if isinstance(value, list):
+            assert all(self._valid_value(v) for v in value)
+        else:
+            assert is_valid_rvalue(value) or isinstance(value, TupleVariable)
+        return True
+
     @property
     def read(self):
-        return self.values
+        return self._unroll(self.values)
 
     @property
     def values(self):