Fixes for undefined names

[PaulKlint]

This pull requests defines code fixes for undefined names. The beauty is that all users of TypePal can directly profit from this. I have implemented a Levenshtein distance metric (that closely follows the formal definition, but is still efficient), to compute the distance between a given variable in a set of possible IdRoles, with what is available in the given TModel.

My questions:

• @jurgenvinju : is this how you envisaged this stylistically?
• I now arbitrarily cutoff suggested names with an edit distance > 3. Should we make this a TypePal configuration parameter?
• Fixes are only generated for real errors, so the computational overhead is minimal.

Suggestions welcome (in particular about how test this in VsCode).

[DavyLandman]

Great stuff! I would like to have a feature to disable this functionality if desired via the config.

[DavyLandman]

Should we configure the memo to timeout after a few minutes?

[PaulKlint]

Yes will do

[jurgenvinju]

Extremely cool.

I was thinking maybe the max config parameter could be part of the require* functions that ultimately produce the code actions lists. That way a language designer can tweak it per identifier role.

[jurgenvinju]

Yes this is exactly what I had in mind stylistically but I'd never dreamed this could be done generically for every typepal client so quickly. Wonder what else you have up your sleeve.

[jurgenvinju]

I agree with you both that an off-switch would be good for if we apply typepal in a non-interactive setting.

[PaulKlint]

Thanks both for reviewing. I will add TypePal configuration parameters

• to turn this behavior off.
• to set the cutoff (although doing this per require* would be nice, unfortunately it breaks the API. In the future when we can add keyword parameters to such functions, we can reconsider this)

[jurgenvinju]

I've added an issue to fix the missing keyword parameter syntax issue. The only reason we don't have this is that we didn't want to change the syntax for a while. Internally all representations of function types already have keyword parameter names and types.