Problem with non-ascii characters in variable names

[woylie]

I encountered a problem with elm-syntax while using elm-analyse on the elm-visualization package.

@jfmengels pointed out that the problem is caused by the variable names ε2 and ρ.

Original issue opened here: stil4m/elm-analyse#242

Elm-analyse returns a FileLoadError (Could not load file due to: Unexpected parse error) for the module Zoom.Interpolation of elm-visualization.

https://github.com/gampleman/elm-visualization/blob/2.1.1/src/Zoom/Interpolation.elm

[MartinSStewart]

I had a look at this. It looks like elm-syntax checks that function names contain only alpha numeric characters. This excludes letters outside of the ascii alphabet.

There doesn't seem to be an easy fix to this because elm-syntax needs to know if a character is uppercase or lowercase and Elm doesn't provide any API for doing that in general with Unicode characters.

[MartinSStewart]

I thought of a hacky solution. We can exploit the fact that String.toLower and String.toUpper do support unicode to implement our own Char.isLower and Char.isUpper

isLower char = 
    let 
         stringChar = String.fromChar char
    in
    case (String.toUpper stringChar == stringChar, String.toLower stringChar == stringChar) of
        (False, True) -> True
        _ -> False

isUpper char = 
    let 
         stringChar = String.fromChar char
    in
    case (String.toUpper stringChar == stringChar, String.toLower stringChar == stringChar) of
        (True, False) -> True
        _ -> False