From ebac009906a00f4cf8976cafabd8e64fd66e6494 Mon Sep 17 00:00:00 2001
From: Semyon Proshev <Semyon.Proshev@jetbrains.com>
Date: Fri, 16 Feb 2018 17:40:42 +0300
Subject: [PATCH] Don't evaluate reference if it resolves to more than one
 elements (PY-19856)

---
 .../src/com/jetbrains/python/psi/impl/PyEvaluator.java   | 7 ++++++-
 python/testSrc/com/jetbrains/python/PyEvaluatorTest.java | 9 +++++++++
 2 files changed, 15 insertions(+), 1 deletion(-)

diff --git a/python/src/com/jetbrains/python/psi/impl/PyEvaluator.java b/python/src/com/jetbrains/python/psi/impl/PyEvaluator.java
index cc71f722a8f5..b6b0e91cd305 100644
--- a/python/src/com/jetbrains/python/psi/impl/PyEvaluator.java
+++ b/python/src/com/jetbrains/python/psi/impl/PyEvaluator.java
@@ -16,6 +16,7 @@
 package com.jetbrains.python.psi.impl;
 
 import com.intellij.psi.PsiElement;
+import com.intellij.psi.ResolveResult;
 import com.intellij.psi.util.PsiTreeUtil;
 import com.intellij.util.containers.ContainerUtil;
 import com.jetbrains.python.PyNames;
@@ -240,7 +241,11 @@ public class PyEvaluator {
       if (myNamespace != null) {
         return myNamespace.get(expression.getReferencedName());
       }
-      PsiElement result = expression.getReference(PyResolveContext.noImplicits()).resolve();
+      final ResolveResult[] results = expression.getReference(PyResolveContext.noImplicits()).multiResolve(false);
+      if (results.length != 1) {
+        return null;
+      }
+      PsiElement result = results[0].getElement();
       if (result instanceof PyTargetExpression) {
         result = ((PyTargetExpression)result).findAssignedValue();
       }
diff --git a/python/testSrc/com/jetbrains/python/PyEvaluatorTest.java b/python/testSrc/com/jetbrains/python/PyEvaluatorTest.java
index e96607330252..aee80fdb0e07 100644
--- a/python/testSrc/com/jetbrains/python/PyEvaluatorTest.java
+++ b/python/testSrc/com/jetbrains/python/PyEvaluatorTest.java
@@ -255,6 +255,15 @@ public class PyEvaluatorTest extends PyTestCase {
     assertTrue(byExpression("not False", Boolean.class));
   }
 
+  public void testMultiResolve() {
+    final PyExpression expression = parseText("if condition:\n" +
+                                              "    a = 1\n" +
+                                              "else:\n" +
+                                              "    a = 3\n" +
+                                              "expr = a < 2");
+    assertNull(new PyEvaluator().evaluate(expression));
+  }
+
   @NotNull
   private <T> T byExpression(@NotNull String expression, @NotNull Class<T> cls) {
     final Object value = new PyEvaluator().evaluate(parseExpression(expression));