Why is `return` not allowed in Kotlin init block?

Question

If I compile this:

class CsvFile(pathToFile : String) {     init      {         if (!File(pathToFile).exists())             return         // Do something useful here     } } 

I get an error:

Error:(18, 13) Kotlin: 'return' is not allowed here

I don't want to argue with the compiler, but I am curious about the motivation behind this restriction.

Answer 1

This is not allowed because of possible counter-intuitive behavior with regard to several init { ... } blocks, which might lead to subtle bugs:

class C {     init {          if (someCondition) return     }     init {         // should this block run if the previous one returned?     } } 

^{If the answer is 'no', the code becomes brittle: adding a return in one init block would affect the other blocks.}

A possible workaround that allows you to finish a single init block is to use some function with lambda and a labeled return:

class C {     init {         run {             if (someCondition) return@run             /* do something otherwise */         }     } } 

Or use an explicitly defined secondary constructor:

class C {     constructor() {          if (someCondition) return          /* do something otherwise */     } }