Fix pretty-printing

Author: Nadrieril

Diff for: compiler/rustc_ast_pretty/src/pprust/state/expr.rs

@@ -919,14 +919,14 @@ impl<'a> State<'a> {
         self.maybe_print_comment(arm.pat.span.lo());
         self.print_outer_attributes(&arm.attrs);
         self.print_pat(&arm.pat);
-        self.space();
         if let Some(e) = &arm.guard {
+            self.space();
             self.word_space("if");
             self.print_expr(e, FixupContext::default());
-            self.space();
         }
 
         if let Some(body) = &arm.body {
+            self.space();
             self.word_space("=>");
 
             match &body.kind {
@@ -951,7 +951,9 @@ impl<'a> State<'a> {
                 }
             }
         } else {
+            // Empty body following a never pattern.
             self.word(",");
+            self.end(); // Close the ibox for the pattern.
         }
         self.end(); // Close enclosing cbox.
     }

Diff for: compiler/rustc_hir_pretty/src/lib.rs

@@ -1880,15 +1880,15 @@ impl<'a> State<'a> {
         self.ibox(0);
         self.print_outer_attributes(self.attrs(arm.hir_id));
         self.print_pat(arm.pat);
-        self.space();
         if let Some(ref g) = arm.guard {
+            self.space();
             self.word_space("if");
             self.print_expr(g);
-            self.space();
         }
 
         match arm.body.kind {
             hir::ExprKind::Block(blk, opt_label) => {
+                self.space();
                 self.word_space("=>");
                 if let Some(label) = opt_label {
                     self.print_ident(label.ident);
@@ -1905,10 +1905,11 @@ impl<'a> State<'a> {
             }
             hir::ExprKind::Unreachable => {
                 // Empty body following a never pattern.
-                self.end(); // close the ibox for the pattern
                 self.word(",");
+                self.end(); // close the ibox for the pattern
             }
             _ => {
+                self.space();
                 self.word_space("=>");
                 self.end(); // close the ibox for the pattern
                 self.print_expr(arm.body);

Diff for: tests/pretty/never_patterns.rs

@@ -0,0 +1,9 @@
+// pp-exact
+#![feature(never_patterns)]
+#![allow(incomplete_features)]
+
+enum Void {}
+
+fn foo(res: &Result<u32, Void>) -> &u32 { match res { Ok(x) => x, Err(!), } }
+
+fn main() { foo(&Ok(0)); }