parameter_assignments

Don't reassign references to parameters of functions or methods.

This rule is available as of Dart 2.0.

DON'T assign new values to parameters of methods or functions.

Assigning new values to parameters is generally a bad practice unless an operator such as ??= is used. Otherwise, arbitrarily reassigning parameters is usually a mistake.

BAD:

void badFunction(int parameter) { // LINT
  parameter = 4;
}

BAD:

void badFunction(int required, {int optional: 42}) { // LINT
  optional ??= 8;
}

BAD:

void badFunctionPositional(int required, [int optional = 42]) { // LINT
  optional ??= 8;
}

BAD:

class A {
  void badMethod(int parameter) { // LINT
    parameter = 4;
  }
}

GOOD:

void ok(String parameter) {
  print(parameter);
}

GOOD:

void actuallyGood(int required, {int optional}) { // OK
  optional ??= ...;
}

GOOD:

void actuallyGoodPositional(int required, [int optional]) { // OK
  optional ??= ...;
}

GOOD:

class A {
  void ok(String parameter) {
    print(parameter);
  }
}

To enable the parameter_assignments rule, add parameter_assignments under linter > rules in your analysis_options.yaml file:

linter:
  rules:
    - parameter_assignments

Unless stated otherwise, the documentation on this site reflects Dart 3.5.4. Page last updated on 2024-07-03. View source or report an issue.