Add a test for typed throws and withUnsafe(Mutable)BufferPointer

Author: DougGregor

test/stdlib/ArrayTypedThrows.swift

@@ -0,0 +1,17 @@
+// RUN: %target-typecheck-verify-swift
+
+enum MyError: Error {
+case fail
+case bad
+}
+
+func unsafeBuffers() throws(MyError) {
+  var a = [1, 2, 3]
+  try a.withUnsafeBufferPointer { (buffer) throws(MyError) in
+    throw .bad
+  }
+
+  try a.withUnsafeMutableBufferPointer { (buffer) throws(MyError) in
+    throw .bad
+  }
+}