Common Kotlin Errors

Using !! on a nullable variable that turned out to be null at runtime.

Accessing a lateinit property before assigning a value to it.

Unsafe cast operator (as) fails due to incompatible runtime object type.

Passing or returning a type that does not match declared function signatures.

Referencing a function, variable, or class name that compiler cannot resolve.

Attempting to assign a new value to an immutable val variable.

Kotlin precondition check require() or check() evaluates to false.

Kotlin compiler cannot guarantee a mutable property var has not been modified between type check and usage.