From 6953939e4af88c0d3219ca5e3f1d661bef115d37 Mon Sep 17 00:00:00 2001
From: Fedor Isakov <fisakov@gmail.com>
Date: Fri, 28 Dec 2018 11:47:46 +0100
Subject: [PATCH] Report unification of a logical with itself as a failure.

---
 reactor/Core/src/jetbrains/mps/logic/reactor/core/Logical.kt | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/reactor/Core/src/jetbrains/mps/logic/reactor/core/Logical.kt b/reactor/Core/src/jetbrains/mps/logic/reactor/core/Logical.kt
index 72bc56d7..adaadbc1 100644
--- a/reactor/Core/src/jetbrains/mps/logic/reactor/core/Logical.kt
+++ b/reactor/Core/src/jetbrains/mps/logic/reactor/core/Logical.kt
@@ -118,6 +118,10 @@ class LogicalImpl<T> : JoinableLogical<T> {
         val thisRepr = this.find()
         val otherRepr = (other as LogicalImpl<T>).find()
 
+        if (thisRepr === otherRepr) {
+            throw IllegalStateException("cannnot unite logical with itself")
+        }
+
         // invariant: thisRepr.rank > otherRepr.rank
         if (thisRepr.rank() < otherRepr.rank()) {
             otherRepr.union(thisRepr, reconciler);