Reports potentially unsafe calls of inline functions with flexible nullable (platform type with unknown nullability) extension receivers.

Before Kotlin 1.2, calls of inline fun with flexible nullable extension receiver (a platform type with an unknown nullability) did not include nullability checks in bytecode. Since Kotlin 1.2, nullability checks are included into the bytecode (see KT-12899).

It's recommended to add an explicit !! you want an exception to be thrown, or consider changing the function's receiver type to nullable if it should work without exceptions.

Example:

  inline fun String.removePrefix(prefix: String): String {
      return this.substring(prefix.length)
  }

  fun main() {
      // `System.getProperty` returns not denotable `String!` type
      val property = System.getProperty("user.dir")
      println(property.removePrefix("/home"))
  }

After the quick-fix is applied:

  inline fun String.removePrefix(prefix: String): String {
      return this.substring(prefix.length)
  }

  fun main() {
      // `System.getProperty` returns not denotable `String!` type
      val property = System.getProperty("user.dir")
      println(property!!.removePrefix("/home"))
  }

This inspection only reports if the Kotlin language level of the project or module is lower than 1.2.