03 Type inference

var lets the initializer determine a local variable's static type.

main() {
  var count = 2
  var title = "New tasks"

  printLine(title)
  printLine(count)

  count = count + 1
  printLine(count)
}

Output:

New tasks
2
3

count is inferred as Integer and title as String. Reassignment still checks the original type; var does not make a variable dynamically typed. An initializer such as null or [] needs a type supplied by context, so it cannot stand alone after var.

Try it: Try changing count = count + 1 to a string assignment and inspect the diagnostic.

Precise rules: Language Reference.