Type Inference example in Kotlin

TypeInference.kt

// val abc: Map<String,Int> = mapOf("a" to 1, "b" to 2, "c" to 3)
// the actual type of the Map is obvious
// thus we can skip Map<String,Int> and let kotlin compiler to make type inference
val abc = mapOf("a" to 1, "b" to 2, "c" to 3)

val abcd = abc + ("d" to 4) // ok!
val abce = abc + ("e" to "5") // compile error: Type mismatch

// val c: Int? = abc["c"]
var c = abc["c"] 

c = "2" // compile error: Type mismatch

// Same Question: 
// If you are asked to refactor from Map<String,Integer> to Map<String,String>,
// try to estimate the efforts!

There will be no compiler error in line 7. The type of the resulting map is inferred as Map<String, Any>.