Print parentheses around arrow function in pipe operator

Related to #1124.

Author: nikic

lib/PhpParser/PrettyPrinter/Standard.php

@@ -426,6 +426,10 @@ protected function pExpr_BinaryOp_Coalesce(BinaryOp\Coalesce $node, int $precede
     }
 
     protected function pExpr_BinaryOp_Pipe(BinaryOp\Pipe $node, int $precedence, int $lhsPrecedence): string {
+        if ($node->right instanceof Expr\ArrowFunction) {
+            // Force parentheses around arrow functions.
+            $lhsPrecedence = $this->precedenceMap[Expr\ArrowFunction::class][0];
+        }
         return $this->pInfixOp(BinaryOp\Pipe::class, $node->left, ' |> ', $node->right, $precedence, $lhsPrecedence);
     }
 

test/code/prettyPrinter/expr/pipe.test

@@ -7,10 +7,16 @@ $a |> $b == $c;
 $c == $a |> $b;
 ($a == $b) |> ($c == $d);
 $a . ($b |> $c) . $d;
+$a |> (fn($x) => $x) |> (fn($y) => $y) |> $b;
+(fn($x) => $x) |> $y;
+fn($x) => $x |> $y;
 -----
 $a |> $b |> $c;
 $a . $b |> $c . $d;
 $a |> $b == $c;
 $c == $a |> $b;
 ($a == $b) |> ($c == $d);
-$a . ($b |> $c) . $d;
+$a . ($b |> $c) . $d;
+$a |> (fn($x) => $x) |> (fn($y) => $y) |> $b;
+(fn($x) => $x) |> $y;
+fn($x) => $x |> $y;