From 11d3cdd5f6994ae197eaf3599f5fcb0cbe2760db Mon Sep 17 00:00:00 2001
From: Chasen Le Hara <chasen@chasenlehara.com>
Date: Tue, 3 Jul 2018 16:10:38 -0700
Subject: [PATCH] Check for can-observation._value instead of .value
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can-observation’s value property is going to be a getter, so now the `._value` property needs to be used.

Related to https://github.com/canjs/can-observation/pull/135
---
 .jshintrc         |  1 +
 scope-key-data.js | 17 ++++++++++++++---
 2 files changed, 15 insertions(+), 3 deletions(-)

diff --git a/.jshintrc b/.jshintrc
index f7840d6..3631bc9 100644
--- a/.jshintrc
+++ b/.jshintrc
@@ -26,6 +26,7 @@
 		"Map": true
 	},
 	"strict": false,
+	"validthis": true,
 	"curly": true,
 	"eqeqeq": true,
 	"freeze": true,
diff --git a/scope-key-data.js b/scope-key-data.js
index a11880f..8e402d5 100644
--- a/scope-key-data.js
+++ b/scope-key-data.js
@@ -106,6 +106,14 @@ var ScopeKeyData = function(scope, key, options){
 
 valueEventBindings(ScopeKeyData.prototype);
 
+function fastOnBoundSet_Value() {
+	this._value = this.newVal;
+}
+
+function fastOnBoundSetValue() {
+	this.value = this.newVal;
+}
+
 Object.assign(ScopeKeyData.prototype, {
 	constructor: ScopeKeyData,
 	dispatch: function dispatch(newVal){
@@ -174,9 +182,12 @@ Object.assign(ScopeKeyData.prototype, {
 
 			return Observation.prototype.dependencyChange.apply(this, arguments);
 		};
-		observation.onBound = function(){
-			this.value = this.newVal;
-		};
+
+		if (observation.hasOwnProperty("_value")) {// can-observation 4.1+
+			observation.onBound = fastOnBoundSet_Value;
+		} else {// can-observation < 4.1
+			observation.onBound = fastOnBoundSetValue;
+		}
 	},
 	toSlowPath: function(){
 		this.observation.dependencyChange = Observation.prototype.dependencyChange;