From 42baa3e5a4a06b295a874277af094991bdffd6af Mon Sep 17 00:00:00 2001
From: Adam Medzinski <adam.medzinski@allegrogroup.com>
Date: Tue, 20 Jun 2017 12:59:03 +0200
Subject: [PATCH] Nil check in Implements assertion

---
 assert/assertions.go      | 5 +++--
 assert/assertions_test.go | 3 +++
 2 files changed, 6 insertions(+), 2 deletions(-)

diff --git a/assert/assertions.go b/assert/assertions.go
index 522017c..847b94b 100644
--- a/assert/assertions.go
+++ b/assert/assertions.go
@@ -280,15 +280,16 @@ func labeledOutput(content ...labeledContent) string {
 //
 //    assert.Implements(t, (*MyInterface)(nil), new(MyObject))
 func Implements(t TestingT, interfaceObject interface{}, object interface{}, msgAndArgs ...interface{}) bool {
-
 	interfaceType := reflect.TypeOf(interfaceObject).Elem()
 
+	if object == nil {
+		return Fail(t, fmt.Sprintf("Cannot check if nil implements %v", interfaceType), msgAndArgs...)
+	}
 	if !reflect.TypeOf(object).Implements(interfaceType) {
 		return Fail(t, fmt.Sprintf("%T must implement %v", object, interfaceType), msgAndArgs...)
 	}
 
 	return true
-
 }
 
 // IsType asserts that the specified objects are of the same type.
diff --git a/assert/assertions_test.go b/assert/assertions_test.go
index 8c64edf..9757792 100644
--- a/assert/assertions_test.go
+++ b/assert/assertions_test.go
@@ -155,6 +155,9 @@ func TestImplements(t *testing.T) {
 	if Implements(mockT, (*AssertionTesterInterface)(nil), new(AssertionTesterNonConformingObject)) {
 		t.Error("Implements method should return false: AssertionTesterNonConformingObject does not implements AssertionTesterInterface")
 	}
+	if Implements(mockT, (*AssertionTesterInterface)(nil), nil) {
+		t.Error("Implements method should return false: nil does not implement AssertionTesterInterface")
+	}
 
 }