Pretty-print parenthesis around binary in postfix match

Signed-off-by: Sasha Pourcelot <sasha.pourcelot@protonmail.com>

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

@@ -488,7 +488,18 @@ impl<'a> State<'a> {
                         self.space();
                     }
                     MatchKind::Postfix => {
+                        let need_par = matches!(expr.kind, ast::ExprKind::Binary(_, _, _));
+
+                        if need_par {
+                            // avoid printing `a + b.match {}`, print
+                            // `(a + b).match {}` instead.
+                            self.popen();
+                        }
                         self.print_expr_as_cond(expr);
+                        if need_par {
+                            self.pclose();
+                        }
+
                         self.word_nbsp(".match");
                     }
                 }

tests/pretty/postfix-match/issue-124206.pp

@@ -0,0 +1,14 @@
+#![feature(prelude_import)]
+#![no_std]
+#![feature(postfix_match)]
+#[prelude_import]
+use ::std::prelude::rust_2015::*;
+#[macro_use]
+extern crate std;
+
+//@ pretty-mode:expanded
+//@ pp-exact:issue-124206.pp
+
+macro_rules! repro { ($e:expr) => { $e.match { _ => {} } }; }
+
+pub fn main() { ({ 1 } + 1).match { _ => {} }; }

tests/pretty/postfix-match/issue-124206.rs

@@ -0,0 +1,16 @@
+#![feature(postfix_match)]
+
+//@ pretty-mode:expanded
+//@ pp-exact:issue-124206.pp
+
+macro_rules! repro {
+    ($e:expr) => {
+        $e.match {
+            _ => {}
+        }
+    };
+}
+
+pub fn main() {
+    repro!({ 1 } + 1);
+}