Programming Kotlin

Type-Safe Builders

A key benefit of using a statically typed language is verifying the soundness of code at compile time. Anytime we deviate from the syntax permitted by the language, the compiler will let us know in no uncertain terms. This prevents a variety of errors from slipping to runtime and thus saves time. When working with DSLs, however, we’re inventing the syntax that’s permitted. The compiler doesn’t have enough details to discern if a particular property access or a method call is legitimate when used within the DSL. This is where type-safe builders come in. Using a special annotation, you can instruct the compiler to keep an eye on the scope of properties and methods. Let’s explore that with a built-in example in Kotlin and then ...