Add a pretty printing test involving a never pattern.

This currently prints badly, with unclosed indentation.

tests/pretty/never-pattern.pp

@@ -0,0 +1,18 @@
+#![feature(prelude_import)]
+#![no_std]
+//@ pretty-mode:expanded
+//@ pp-exact:never-pattern.pp
+//@ only-x86_64
+
+#![allow(incomplete_features)]
+#![feature(never_patterns)]
+#![feature(never_type)]
+#[prelude_import]
+use ::std::prelude::rust_2015::*;
+#[macro_use]
+extern crate std;
+
+fn f(x: Result<u32, !>) {
+    _ = match x { Ok(x) => x, Err(!) , }; }
+
+    fn main() {}

tests/pretty/never-pattern.rs

@@ -0,0 +1,16 @@
+//@ pretty-mode:expanded
+//@ pp-exact:never-pattern.pp
+//@ only-x86_64
+
+#![allow(incomplete_features)]
+#![feature(never_patterns)]
+#![feature(never_type)]
+
+fn f(x: Result<u32, !>) {
+    _ = match x {
+        Ok(x) => x,
+        Err(!),
+    };
+}
+
+fn main() {}