Unexpected result with variable inside an <xf:bind> iteration

[ebruchez]

Repro:

1. Run https://gist.github.com/823402 in the XForms Sandbox
2. Enter text in the 2 fields => the concatenation shows at the end of the line
3. Click the "Insert" button => concatenation is shown as empty

Main issue is that we haven't properly determined what's the correct behavior in this case. Options:

• lexical scoping, i.e. preceding::bind
• same level or ancestor
• any, similar to id resolution w/ repeat iterations (except binds don't have a current index)

Also, distinction between:

• MIP accessing bind as variable
• `bind/@ref`` accessing bind as variable (currently not supported at all)

Moved from:

http://forge.ow2.org/tracker/index.php?func=detail&aid=315833&group_id=168&atid=350207

[ebruchez]

Checked that this is still broken now.

Notes from 2011:

• implement better variable resolution strategy as discussed w/ Alex 2011-02-11
• also check static analysis of expressions
• issue: XFModelBinds.getVariables() is not implemented right
• Q: what algorithm should be used to find variable?
  • A: find "closest bind", similar to id resolution w/ repeats
  • find common ancestor bind if any
  • use that as starting point
  • then drill down from there, use 1st branch if more than 1
• enforce unicity of @name on binds within model

[ebruchez]

This sample must work one this is fixed.

[ebruchez]

Now documented.