Auto merge of #31915 - nagisa:mir-unpretty-fix, r=arielb1

Fixes #31913

Author: bors

src/librustc_driver/pretty.rs

@@ -817,13 +817,12 @@ pub fn pretty_print_input(sess: Session,
                                                              &id,
                                                              resolve::MakeGlobMap::No,
                                                              |tcx, mir_map, _, _| {
-                let mir_map = mir_map.unwrap();
-
-                for (nodeid, mir) in &mir_map.map {
-                    try!(writeln!(out, "MIR for {}", tcx.map.node_to_string(*nodeid)));
-                    try!(write_mir_pretty(mir, &mut out));
+                if let Some(mir_map) = mir_map {
+                    for (nodeid, mir) in &mir_map.map {
+                        try!(writeln!(out, "MIR for {}", tcx.map.node_to_string(*nodeid)));
+                        try!(write_mir_pretty(mir, &mut out));
+                    }
                 }
-
                 Ok(())
             }), &sess)
         }
@@ -840,12 +839,14 @@ pub fn pretty_print_input(sess: Session,
                                                              &id,
                                                              resolve::MakeGlobMap::No,
                                                              |tcx, mir_map, _, _| {
-                let mir_map = mir_map.unwrap();
-                try!(writeln!(out, "MIR for {}", tcx.map.node_to_string(nodeid)));
-                let mir = mir_map.map.get(&nodeid).unwrap_or_else(|| {
-                    sess.fatal(&format!("no MIR map entry for node {}", nodeid))
-                });
-                write_mir_pretty(mir, &mut out)
+                if let Some(mir_map) = mir_map {
+                    try!(writeln!(out, "MIR for {}", tcx.map.node_to_string(nodeid)));
+                    let mir = mir_map.map.get(&nodeid).unwrap_or_else(|| {
+                        sess.fatal(&format!("no MIR map entry for node {}", nodeid))
+                    });
+                    try!(write_mir_pretty(mir, &mut out));
+                }
+                Ok(())
             }), &sess)
         }
 

src/test/compile-fail/mir-unpretty.rs

@@ -0,0 +1,15 @@
+// Copyright 2015 The Rust Project Developers. See the COPYRIGHT
+// file at the top-level directory of this distribution and at
+// http://rust-lang.org/COPYRIGHT.
+//
+// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
+// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
+// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
+// option. This file may not be copied, modified, or distributed
+// except according to those terms.
+
+// compile-flags: -Z unstable-options --unpretty=mir
+
+fn main() {
+    let x: () = 0; //~ ERROR: mismatched types
+}