<ul><li>Opaque types allow developers to wrap common primitive types, such as Int or String, to ensure that different concepts are not accidentally interchanged.</li><li>They provide a way to hide the logic or data associated with a type, exposing only controlled extension methods and maintaining full control over how the type is used.</li><li>Extension methods for opaque types can be placed in a separate object, allowing for selective importing and isolation from other methods with the same name.</li><li>Exporting extension methods using 'export' keyword brings them into scope and allows them to be called.</li></ul>

Scala in the Boudoir: Lifting the Veil on Opaque Types and Exporting Our Secrets

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