55 lines
1.4 KiB
Plaintext
55 lines
1.4 KiB
Plaintext
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== Why is this an issue?
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In Dart, `const` is used to declare compile-time constants. It can also be used to declare constant values, typically provided by https://dart.dev/language/constructors#constant-constructors[constant constructors]. This constructor, if used within `const` context will create an instance as a compile-time constant. This is an example of usage of a constant constructor:
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Declaration
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[source,dart]
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----
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class Person {
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final int age;
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final String name;
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const Point(this.age, this.name);
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}
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----
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Usage
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[source,dart]
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----
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void f() {
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var p = const Person(40, 'A');
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var family = const [Person(40, 'A'), Person(39, 'B')];
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}
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----
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When you're already inside the `const` context, there's no need to repeat the keyword. So instead of writing `const [const Person(40, 'A'), const Person(39, 'B')]` you can just write `const [Person(40, 'A'), Person(39, 'B')]`.
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This rule raises an issue when `const` modifier was used within another `const` context
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=== Noncompliant code example
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[source,dart]
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----
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void f() {
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var family = const [const Person(40, 'A'), const Person(39, 'B')];
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}
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----
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=== Compliant solution
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[source,dart]
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----
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void f() {
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var family = const [Person(40, 'A'), Person(39, 'B')];
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}
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----
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== Resources
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* https://dart.dev/tools/linter-rules/unnecessary_const[Dart Lint rule]
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* https://dart.dev/language/constructors#constant-constructors[Constant constructors]
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* https://dart.dev/language/classes[Dart classes]
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