Allow const or const let to be used within function scope

[matiwinnetou]

Having read https://aiken-lang.org/language-tour/variables-and-constants, initially I thought that it is possible to use const in functions but unfortunately this is not the case. Very recently I had a case of the following method which using let of course works "fine"

test my_first_test() {
  let b1: ByteArray = #[1]
  let b2: ByteArray = #[2]

  let b1: Bool = True
  let b2: Bool = True

  b1 && b2
}

in this case it seems harmless but I would much prefer to get a compilation error on code like this:

test my_first_test() {
  const b1: ByteArray = #[1]
  const b2: ByteArray = #[2]

  const b1: Bool = True
  const b2: Bool = True

  b1 && b2
}

or

  const b1: ByteArray = #[1]
  const b2: ByteArray = #[2]

  b1 = True
  b2 = True
  b1 = #[3]
  b2 = #[4]

  b1 && b2

I should not be able to change types and change values in the type of consts.

I personally don't like that we don't have support for const in function scope, in every programming language there should be a way to specify immutable local variables within function scope and hence in:

• java - we have final and final static [what current const does I guess]
• scala - we have val
• JavaScript / TypeScript - we have const, const can be specified within function scope

Please add support for const in functions or some new keyword, e.g. const let.

[rvcas]

All variables are already immutable. And shadowing is supported. const is just a way to define values at the module level. They don't even parse inside of function body expressions. I know Javascript has their differences between const and let but even then it has nothing to do with mutability but instead is related to re-binding. There's really no value to have const in expressions and we intend on allowing shadowing to be supported for the for seeable future. Our const simply just means a different thing than the one in javascript. Just because we decided to use the keyword const for module level values doesn't mean we need to satisfy the same use cases of other languages that happen to have the same keyword.

[matiwinnetou]

I see, I was not aware that let is already immutable but then why confuse a developer? Everything should be a const and we should have no let keyword at all. It only confuses... or?