From cdedbcdea77fcfe46459cdba7019bfe7cb819821 Mon Sep 17 00:00:00 2001
From: Robert Payne <robertpayne@me.com>
Date: Sat, 10 Sep 2016 16:38:40 +1200
Subject: [PATCH] Fix bug where pinning composite to composite would fail

---
 Source/Constraint.swift |  6 +++---
 Tests/Tests.swift       | 22 ++++++++++++++++++++++
 2 files changed, 25 insertions(+), 3 deletions(-)

diff --git a/Source/Constraint.swift b/Source/Constraint.swift
index 2491c7b..0bfce79 100644
--- a/Source/Constraint.swift
+++ b/Source/Constraint.swift
@@ -82,7 +82,7 @@ public class Constraint {
             // get layout to attribute
             let layoutToAttribute: NSLayoutAttribute
             #if os(iOS) || os(tvOS)
-                if layoutToAttributes.count > 1 {
+                if layoutToAttributes.count > 0 {
                     if self.from.attributes == .edges && self.to.attributes == .margins {
                         switch layoutFromAttribute {
                         case .left:
@@ -109,11 +109,11 @@ public class Constraint {
                         default:
                             fatalError()
                         }
+                    } else if self.from.attributes == self.to.attributes {
+                        layoutToAttribute = layoutFromAttribute
                     } else {
                         layoutToAttribute = layoutToAttributes[0]
                     }
-                } else if layoutToAttributes.count == 1 {
-                    layoutToAttribute = layoutToAttributes[0]
                 } else {
                     layoutToAttribute = layoutFromAttribute
                 }
diff --git a/Tests/Tests.swift b/Tests/Tests.swift
index 5c37c95..1896d8d 100644
--- a/Tests/Tests.swift
+++ b/Tests/Tests.swift
@@ -441,6 +441,28 @@ class SnapKitTests: XCTestCase {
         
     }
     
+    func testEdgesToEdges() {
+        var fromAttributes = Set<NSLayoutAttribute>()
+        var toAttributes = Set<NSLayoutAttribute>()
+        
+        let view = View()
+        self.container.addSubview(view)
+        
+        view.snp.remakeConstraints { (make) -> Void in
+            make.edges.equalTo(self.container.snp.edges)
+        }
+        
+        XCTAssertEqual(self.container.snp_constraints.count, 4, "Should have 4 constraints")
+        
+        for constraint in (container.snp_constraints as! [NSLayoutConstraint]) {
+            fromAttributes.insert(constraint.firstAttribute)
+            toAttributes.insert(constraint.secondAttribute)
+        }
+        
+        XCTAssert(fromAttributes == [.top, .left, .bottom, .right])
+        XCTAssert(toAttributes == [.top, .left, .bottom, .right])
+    }
+    
     func testLayoutGuideConstraints() {
         let vc = UIViewController()
         vc.view = UIView(frame: CGRect(x: 0, y: 0, width: 300, height: 300))