定義:

型別安全(type safety)可以靜態方式實施，及早在編譯時期就捕捉到潛藏的錯誤；或者以動態方式，在執行時期關聯型別的資訊，並在必要時檢測即將發生的錯誤。型別安全是程式語言的性質，而不是程式所自有的。例如，有可能以型別不安全的語言，編寫出型別安全的程式。在此是以程式語言為主，而不討論以個人能力維護的型別安全。(p.s. 以上內容來自Wiki)

Note:

針對Swift語言:

Swift is a type-safe language, which means the language helps you to be clear about the types of values your code can work with. If part of your code requires a String, type safety prevents you from passing it an Int by mistake. Likewise, type safety prevents you from accidentally passing an optional String to a piece of code that requires a non-optional String. Type safety helps you catch and fix errors as early as possible in the development process.

優缺點:

優點: 能讓開發者在開發時提早發現錯誤 (p.s. 在靜態語言狀況下)

Ref:

https://stackoverflow.com/questions/260626/what-is-type-safe

https://zh.wikipedia.org/wiki/%E5%9E%8B%E5%88%A5%E5%AE%89%E5%85%A8

https://docs.swift.org/swift-book/LanguageGuide/TheBasics.html