CODEWITHSUNDEEP
scalasbtscala-compiler
samthebest
samthebest

Reputation: 31543

Is there a Scala compiler flag to warn when tail recursion is applied without annotation?

I would like the compiler to warn me when it applies tail recursion to one of my functions when I haven't told it to with the annotation. Is this possible?

Motivation: I very rarely write infinite loops as a matter of logic error, but I have done with typos (yes it is possible). Usually recursive infinite loops just tell you what is wrong with a stack overflow exception, but not if they get compiled tail recursively, it just hangs.

Forgetting the new keyword in combination with case classes with default params is a good example that I have foolishly stumbled on twice:

case class A(a: Int, b: Int = 1)

object A {
  def apply(a: Int): A = A(a)

Causes an infinite loop with no SO, but def apply(a: Int): A = new A(a) does not

Upvotes: 2

Views: 441

Answers (2)

Dima
Dima

Reputation: 40510

Avoid declaring function return types when practical: def apply(a: Int) = A(a) would fail to compile, so you would know that something is wrong.

Upvotes: 0

Daenyth
Daenyth

Reputation: 37461

I don't think the compiler has this but IntelliJ offers a "No tail recursion annotation" under Inspections > Scala: General

Detects tail recursive methods without @tailrec annotation which verifies that the method will be compiled with tail call optimization.

Upvotes: 3

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