Error when defining variables in different scopes

[pmenon]

TPL allows variables with the same name to be declared in different scopes. However, during bytecode generation, variables are resolved by performing a linear start-to-end lookup in the function's frame. This may not always be correct.

Example TPL:

fun main() -> int {
  var a = 2
  if (a < 10) {
    var b = 8
    if (a < b) {
      var b = 5
      if (a < b) {
        var b = 1
        if (a < b) {
          return 100
        }
      }
    }
  }
  return 2
}

One solution is to automatically uniq-ify all variable names internally, but we'll need to add extra metadata to the AST nodes. A simpler solution is to perform the linear search from inner-most scope to outer-most scope (as is done during semantic checks).

[lmwnshn]

Reminds me strongly of 312. We were taught that alpha-conversion is the one true way to do this, but I'll go look at what real compilers are doing for a bit.

[lmwnshn]

I think this rightfully would call for something like de Bruijn indexes or Haskell's rapier, e.g. as described on [1]. But I can start by doing the dumb thing. I'm trying to figure out if there's a reason other people aren't doing the dumb thing.

[1] https://www.schoolofhaskell.com/user/edwardk/bound