prefer_immediate_return

v0.8.0 Warning Fix Code Quality

This rule flags a local variable that is declared and then returned on the very next line, with no other use.

Why use this rule

The variable adds a name but no information — the return statement already says what the value is for. It also adds a line that has to be kept in sync: rename the variable and two places change instead of none.

Don’t

class Cart {
  const Cart(this.lines);
  final List<CartLine> lines;

  int subtotal() {
    final total = lines.fold(0, (sum, line) => sum + line.amount);
    return total;
  }
}

class CartLine {
  const CartLine(this.amount);
  final int amount;
}

Do

class Cart {
  const Cart(this.lines);
  final List<CartLine> lines;

  int subtotal() {
    return lines.fold(0, (sum, line) => sum + line.amount);
  }
}

class CartLine {
  const CartLine(this.amount);
  final int amount;
}

In an `async` method, keep the `await`

The rule reports the same shape inside an async body. Inline the initializer with its await — dropping it leaves an async method with no await, which avoid_redundant_async then reports, and both rules are in opinionated:

class Api {
  Future<String> fetchUser(String id) async => id;
}

class Screen {
  Screen(this.api);

  final Api api;

  // Don't
  Future<String> loadBad(String id) async {
    final user = await api.fetchUser(id);
    return user;
  }

  // Do
  Future<String> loadGood(String id) async {
    return await api.fetchUser(id);
  }
}

Known limitations

The rule reports only when the variable is provably throwaway:

It is the second-to-last statement, directly followed by return name;.
The declaration declares exactly one variable — var a = 1, b = 2; is skipped.
It has an initializer and is not late.
The returned identifier resolves to that declaration, not a field or outer variable with the same name.
The variable is referenced exactly once in the whole function body — the return itself.

A variable kept deliberately as documentation (final isEligible = ...; return isEligible;) will be reported. If the name earns its place, suppress the diagnostic on that line.

Configuration

This rule is in the opinionated preset, so it is on with preset: opinionated, or by name:

rules:
  prefer_immediate_return: true

To turn it off again:

rules:
  prefer_immediate_return: false

To keep the rule on but skip certain paths, use per-rule exclude.

prefer_early_return — Replace a body-wrapping if with an early-return guard.
avoid_collapsible_if — Merge nested if statements with &&.
avoid_redundant_else — Drop the else when the if branch always exits.
avoid_accessing_other_classes_private_members — Make the underscore mean what everyone reads it as.