Nullsafe Pipe

The nullsafe pipe operator, |?>, is a variant of the pipe operator designed for nullable expressions. It evaluates the left-hand expression and, if the result is null, short-circuits the entire expression to null without evaluating the right-hand side. If the result is non-null, it binds the value to $$ with nullability stripped and evaluates the right-hand expression.

The result type of e1 |?> e2 is always ?ty2 — even if e2 would return a non-nullable type on its own, the overall expression can still be null because of the short-circuit.

Basic Usage

function foo(bool $coinflip): ?string {
  return $coinflip ? "foo" : null;
}

function bar(string $prefix): string {
  return $prefix."bar";
}

function example(bool $coinflip): void {
  // $$ is refined to string (not ?string), so bar() accepts it.
  // The result is ?string because |?> may short-circuit to null.
  $result = foo($coinflip) |?> bar($$);
}

Without the nullsafe pipe, you would need an explicit null check:

function example_without(bool $coinflip): void {
  $tmp = foo($coinflip);
  $result = $tmp is nonnull ? bar($tmp) : null;
}