[Solved] Why does Kotlin not apply smart casts to a var variable inside a when expression? — Ans: Because the variable can be reassigned, making type unsafe. | Kotlin

Kotlin - Control Flow as Expressions

Why does Kotlin not apply smart casts to a var variable inside a when expression?

ABecause <code>when</code> does not support smart casts.

BBecause smart casts only work with <code>val</code> declared inside functions.

CBecause <code>var</code> variables are always nullable.

DBecause the variable can be reassigned, making type unsafe.

Step-by-Step Solution

Solution:

Step 1: Recall smart cast requirements
Smart casts require variables to be stable and not reassigned.
Step 2: Understand mutability impact
var variables can be reassigned, so Kotlin cannot guarantee type safety for smart casts.
Final Answer:
Because the variable can be reassigned, making type unsafe. -> Option D
Quick Check:
Mutability prevents smart cast [OK]

Quick Trick: Mutable vars prevent smart casts due to reassignment risk [OK]

Common Mistakes:

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