avoid_unnecessary_constructor

v1.0.0 Warning Code Organization

This rule flags an empty unnamed constructor that matches the one Dart provides when no constructor is declared at all.

Why use this rule

class A { A(); } writes out exactly the default: no parameters, no initializers, no body, no documentation. The line adds nothing a reader can act on, and it invites the assumption that construction does something.

Several shapes are deliberately not reported, because each does something the implicit constructor cannot:

• const A(); — lets callers write const A().
• A named or private constructor.
• A documented or annotated one, which carries information even when empty.
• Any class with a second constructor: Dart only supplies the unnamed one when no constructor is written, so there the empty A() is what keeps A() legal.

Don’t

class Repository {
  Repository();
}

Do

class Repository {}

Turning this rule off

This rule is in the opinionated preset.

To disable this rule:

many_lints.yaml

rules:
  avoid_unnecessary_constructor: false

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

Related rules

• arguments_ordering — Keep named arguments in a configured order.
• avoid_duplicate_mixins — Flag a mixin applied twice in one with clause.
• avoid_generics_shadowing — Avoid generic type parameters that shadow top-level declarations.
• avoid_unnecessary_extends — Remove an explicit extends Object.