[Gambas-bugtracker] Bug #1361: Declare variables anywhere and more lexical scope

[bugtracker at gambaswiki.org]

http://gambaswiki.org/bugtracker/edit?object=BUG.1361&from=L21haW4-

Tobias BOEGE reported a new bug.

Summary
-------

Declare variables anywhere and more lexical scope

Type             : Request
Priority         : Medium
Gambas version   : Unknown
Product          : Language


Description
-----------

A feature request for Gambas 4.0, but that's not an option for the "Gambas version" label.

(1) I want the ability to Dim local variables anywhere in a function:

    Dim i As Integer = 12
    
    Print i
    i = 15
    Dim j As Integer = i ^ 2
    Print j

This is not as easy as having the parser pretend the variable declaration occured at the
top of the function, because the initialisation of j depends on statements written before
the declaration.

(2) It would be nice if IF, FOR, FOR EACH, DO, WHILE, REPEAT, CASE and WITH provided a new
lexical scope, i.e. any variable you declare in these blocks is only available (lexically-)
inside the block.

    Dim i As Integer
    
    For i = 1 To 10
      Dim j As Integer = i ^ 2
      Print j
    Next
    
    Print j ' error, variable j is unknown here
    
    For i = 1 To 10
      Dim j As Integer = i - 1
      Print j ' allowed, this is a new lexical scope
    Next

Bonus points for a documented decision on what should happen when a variable is re-declared
in a tighter lexical scope:

    For i = 1 To 10
      Dim i As Integer = 100
      Print i
    Next

To me, it would make sense to either forbid that altogether, or allow the redeclaration with
the following semantics: the outer loop uses the i from the enclosing scope, i.e. the loop
is really executed 10 times, and inside the loop you print the contents of a new variable.
(That means you can lose access to your loop variable if you want to.)