How Type Safety is implemeted in Swift 4?

Swift 4 is a type-safe language which means if a part of your code expects a String, you can’t pass it an Int by mistake. As Swift 4 is type-safe, it performs type-checks when compiling your code and flags any mismatched types as errors.

 
import Cocoa

var myVar = 42
myVar = "This is a sample String"
print(myVar)

Playground execution failed: error: :6:6: error: cannot assign to ‘let’ value ‘myVar’

myVar = “This is a sample String”

When we compile the above program, it produces the following compile time error.