Merge pull request #10461 from practicalswift/swiftc-28790-conformance-getwitness-requirement-nullptr-getdecl-already-have-a-non-optional-w

[swiftc (32 vs. 5565)] Add crasher in swift::TypeChecker::resolveWitness

Author: practicalswift

validation-test/compiler_crashers/28790-conformance-getwitness-requirement-nullptr-getdecl-already-have-a-non-optional-w.swift

@@ -0,0 +1,10 @@
+// This source file is part of the Swift.org open source project
+// Copyright (c) 2014 - 2017 Apple Inc. and the Swift project authors
+// Licensed under Apache License v2.0 with Runtime Library Exception
+//
+// See https://swift.org/LICENSE.txt for license information
+// See https://swift.org/CONTRIBUTORS.txt for the list of Swift project authors
+
+// REQUIRES: asserts
+// RUN: not --crash %target-swift-frontend %s -emit-ir
+class a:P{class a{}{}func a:a{}func a{}}@objc protocol P{{}func a