From 7c0a4a68ad6b6c780eb41249c6627b8dd7b42524 Mon Sep 17 00:00:00 2001
From: Dan Fabulich <dan@fabulich.com>
Date: Tue, 7 Nov 2017 07:44:02 -0800
Subject: [PATCH] Better error message when value missing after operator

---
 tests/scenetest.js | 7 +++++++
 web/scene.js       | 4 ++++
 2 files changed, 11 insertions(+)

diff --git a/tests/scenetest.js b/tests/scenetest.js
index 758e7d54..85656584 100644
--- a/tests/scenetest.js
+++ b/tests/scenetest.js
@@ -1141,6 +1141,13 @@ test("errorMissingOperator", function() {
     doh.is([{"value":"3","name":"NUMBER","pos":1},{"value":"3","name":"NUMBER","pos":3}], stack, "stack");
     doh.assertError(Error, scene, "evaluateExpr", stack, "Invalid expression");
 })
+test("errorMissingValueAfterOperator", function() {
+    var scene = new Scene();
+    var stack = scene.tokenizeExpr("3 =");
+    //print(toJson(stack))
+    doh.is([{"name":"NUMBER","value":"3","pos":1},{"name":"EQUALITY","value":"=","pos":3}], stack, "stack");
+    doh.assertError(Error, scene, "evaluateExpr", stack, "Invalid expression");
+})
 test("errorEmptyStack", function() {
     var scene = new Scene();
     doh.assertError(Error, scene, "evaluateExpr", [], "Invalid expression");
diff --git a/web/scene.js b/web/scene.js
index 2b4ea181..9adb59af 100644
--- a/web/scene.js
+++ b/web/scene.js
@@ -3473,6 +3473,10 @@ Scene.prototype.evaluateExpr = function evaluateExpr(stack, parenthetical) {
       this.warning("For more details on modulo, see: https://forum.choiceofgames.com/t/21176");
     }
 
+    if (!stack[0]) {
+      throw new Error(this.lineMsg() + "Invalid expression at char "+token.pos+", expected something after a "+token.value);
+    }
+
     if (stack[0].func == "auto") {
       value2 = this.autobalance(stack, token, value1);
     } else {