falcon

Rules / Style / unnecessary-new

unnecessary-new

lint/style/unnecessary-new
recommended
Same as unnecessary_new · Dart lints

Flags an explicit new keyword in an instance-creation expression.

Since Dart 2.0 the new keyword is always optional: new Foo() and Foo() construct identically. Keeping new is pure noise and breaks visual consistency with the surrounding code, which almost always omits it. The rule only targets explicit new; an implicit Foo() parses as a call and a const Foo() keeps its const, so neither is touched. Delete the new.

Invalid

example.dartdart
// Bad: explicit `new` keyword, which is always optional.
class Foo {
  Foo();
  Foo.named();
}

void examples() {
  final a = new Foo();
  final b = new Foo.named();
  final c = new List<int>.empty();
  final d = new StringBuffer();
  final e = new Foo()..toString();
  final f = [new Foo()];
  print([a, b, c, d, e, f]);
}
Unnecessary `new` keyword; it is optional and can be removed.
7void examples() {
8 final a = new Foo();
Unnecessary `new` keyword; it is optional and can be removed.
8 final a = new Foo();
9 final b = new Foo.named();
Unnecessary `new` keyword; it is optional and can be removed.
9 final b = new Foo.named();
10 final c = new List<int>.empty();
Unnecessary `new` keyword; it is optional and can be removed.
10 final c = new List<int>.empty();
11 final d = new StringBuffer();
Unnecessary `new` keyword; it is optional and can be removed.
11 final d = new StringBuffer();
12 final e = new Foo()..toString();
Unnecessary `new` keyword; it is optional and can be removed.
12 final e = new Foo()..toString();
13 final f = [new Foo()];

Valid

example.dartdart
// Good: instance creation without the `new` keyword.
class Foo {
  Foo();
  Foo.named();
}

void examples() {
  final a = Foo();
  final b = Foo.named();
  final c = StringBuffer();
  final d = <int>[1, 2, 3];
  final e = <int>{};
  final f = 'a literal';
  print([a, b, c, d, e, f]);
}

How to configure

Set the severity of unnecessary-new in your falcon.json:

falcon.jsonjson
{
  "linter": {
    "rules": {
      "style": {
        "unnecessary-new": "error"
      }
    }
  }
}

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