Rollup merge of #140246 - nnethercote:fix-never-pattern-printing, r=Nadrieril

Fix never pattern printing

It's currently broken, but there's an easy fix.

r? `@Nadrieril`

compiler/rustc_ast_pretty/src/pprust/state/expr.rs

@@ -876,6 +876,7 @@ impl<'a> State<'a> {
                 }
             }
         } else {
+            self.end(); // Close the ibox for the pattern.
             self.word(",");
         }
         self.end(); // Close enclosing cbox.

tests/pretty/never-pattern.pp

@@ -0,0 +1,17 @@
+#![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() {}