16f6c0aecf
Inline adoc files when they are included exactly once. Also fix language tags because this inlining gives us better information on what language the code is written in.
58 lines
1.7 KiB
Plaintext
58 lines
1.7 KiB
Plaintext
== Why is this an issue?
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The TypeScript type system offers a basic support for composite types:
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* _Union Types_ represent a value that can be one of the several types. They are constructed using a vertical bar (``++|++``) like the following ``++type NumberOrString = number | string++``.
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* _Intersection Types_ combine multiple types into one, so that the object of such type will have all the members of all intersection type elements. They are constructed using an ampersand (``++&++``) like the following ``++type SerializablePerson = Person & Serializable++``. Intersection Types are often used to represent mixins.
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Duplicating types when defining a union or interaction type makes the code less readable. Moreover duplicated types might be a simple mistake and another type should be used instead.
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=== Noncompliant code example
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[source,javascript]
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----
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function padLeft(value: string, padding: string | number | string) { // Noncompliant; 'string' type is used twice in a union type declaration
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// ...
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}
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function extend(p : Person) : Person & Person & Loggable { // Noncompliant; 'Person' is used twice
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// ...
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}
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----
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=== Compliant solution
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[source,javascript]
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----
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function padLeft(value: string, padding: string | number | boolean) {
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// ...
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}
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function extend(p : Person) : Person & Loggable {
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// ...
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}
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----
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ifdef::env-github,rspecator-view[]
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'''
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== Implementation Specification
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(visible only on this page)
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=== Message
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Remove this duplicated type or replace with another one.
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=== Highlighting
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First: second occurrence of the element
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Second: first occurrence ("Original"), third and all other occurrences ("Another duplicate")
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endif::env-github,rspecator-view[]
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