always_specify_types

Missing type annotation.

The analyzer produces this diagnostic when an explicit type annotation is missing.

This includes in the following cases:

• A variable declaration that uses var, final, or const without a specific type.
• A function parameter lacks a type annotation.
• A collection literal lacks explicit type arguments.
• A reference to a generic class, mixin, or enum lacks type arguments.

Types annotated with @optionalTypeArgs from package:meta are exempt from requiring type arguments.

The following code produces this diagnostic because the top-level variable uses var without an explicit type:

var x = 1;

The following code produces this diagnostic because the parameter p lacks a type annotation:

void f(p) {}

The following code produces this diagnostic because the set literal lacks an explicit type argument:

Set<int> items = {1, 2};

The following code produces this diagnostic because the generic type C is used without specifying its type argument:

class C<T> {}
​
C c = C<int>();

Add an explicit type annotation to variable declarations:

int x = 1;

Add a type annotation to parameters:

void f(int p) {}

Add explicit type arguments to collection literals:

Set<int> items = <int>{1, 2};

Add type arguments to generic type references:

class C<T> {}
​
C<int> c = C<int>();

If a type argument is meant to be optional, annotate the declaration with @optionalTypeArgs from package:meta to exempt it from this lint:

import 'package:meta/meta.dart';
​
@optionalTypeArgs
class C<T> {}
​
C c = C();