[Solved] In Kotlin, which condition allows smart casting inside a when expression? — Ans: When the variable is immutable or not modified after the check. | Kotlin

Kotlin - Control Flow as Expressions

In Kotlin, which condition allows smart casting inside a when expression?

AWhen the variable is declared inside a function only.

BWhen the variable is declared as <code>var</code> and changed inside <code>when</code>.

CWhen the variable is a primitive type only.

DWhen the variable is immutable or not modified after the check.

Step-by-Step Solution

Solution:

Step 1: Identify smart cast requirements
Kotlin smart casts work only if the variable is immutable or not changed after the type check.
Step 2: Understand mutability impact
If the variable is mutable and changed, Kotlin cannot guarantee type safety, so smart cast is not applied.
Final Answer:
When the variable is immutable or not modified after the check. -> Option D
Quick Check:
Smart casts require immutability or no modification [OK]

Quick Trick: Smart casts need stable (unchanged) variables [OK]

Common Mistakes:

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In Kotlin, which condition allows smart casting inside a when expression?