prefer_explicit_parameter_names

v1.0.0WarningConfigurableType Annotations

This rule flags a function type — in a typedef or a function-typed parameter — that declares unnamed parameters.

This rule is in the pedantic preset.

Why use this rule

void Function(String, int) tells a reader the types and nothing else. At the point where someone writes the callback, (String, int) gives them two anonymous values to guess at — is the int an index, a count, an id?

void Function(String label, int count) answers that in the signature, where the answer belongs, and IDEs echo those names into the closure they generate.

A single-parameter function type is exempt by default: void Function(T) is unambiguous from the type alone, and naming it adds nothing.

See also: Effective Dart: type annotations

Don’t

typedef OnChanged = void Function(String, int);

void listen(void Function(String, int) callback) {}

Do

typedef OnChanged = void Function(String label, int count);

void listen(void Function(String label, int count) callback) {}

// Exempt by default — unambiguous from the type alone.
typedef OnTap = void Function(String);

Options

analysis_options.yaml

analysis_options.yaml

many_lints:
  rules:
    prefer_explicit_parameter_names:
      min_parameters: 2

many_lints.yaml

many_lints.yaml

rules:
  prefer_explicit_parameter_names:
    min_parameters: 2

Option	Type	Default	Description
min_parameters	int	2	Fewest parameters a function type must have before names are required

Turning this rule off

To disable this rule:

many_lints.yaml

rules:
  prefer_explicit_parameter_names: false

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

Related rules

• prefer_explicit_function_type — Prefer explicit function type annotations over the bare ‘Function’ type.
• prefer_typedefs_for_callbacks — Name a multi-parameter function type with a typedef.
• prefer_void_callback — Use ‘VoidCallback’ instead of ‘void Function()’.
• prefer_explicit_type_arguments — Pin the type arguments of the APIs where inference surprises.