add ‘url’ parameter to type constructors to improve error messages

[davidchambers]

//    inc :: FiniteNumber -> FiniteNumber
const inc = def('inc', {}, [$.FiniteNumber, $.FiniteNumber], x => x + 1);

inc(Infinity);
// ! TypeError: Invalid value
//
//   inc :: FiniteNumber -> FiniteNumber
//          ^^^^^^^^^^^^
//               1
//
//   1)  Infinity :: Number
//
//   The value at position 1 is not a member of ‘FiniteNumber’.
//
//   See https://github.com/sanctuary-js/sanctuary-def/tree/v0.7.0#FiniteNumber for information about the sanctuary-def/FiniteNumber type.

The link to the type's documentation strikes me as useful. What do you think? It makes defining types a bit less convenient, but provides a benefit to those who use functions defined via sanctuary-def.

Using version-specific URLs is a good idea as a type may be deleted or its meaning may change.

[davidchambers]

This means one can simply use '' as the url of an undocumented type.

[safareli]

can we get it from package.json

[davidchambers]

Not in the browser, unfortunately.

[safareli]

What about something like this? (this names are not perfect)

$.FiniteNumber = withURL('sanctuary-def/FiniteNumber', (name, url) => NullaryType(
  name, url,
  function(x) { return $.ValidNumber._test(x) && isFinite(x); }
));
// or 
$.FiniteNumber = typeWithURL(
  'sanctuary-def/FiniteNumber',
  NullaryType,
  function(x) { return $.ValidNumber._test(x) && isFinite(x); }
);

Whis way we would not need this switch statement. And it will eliminate need to update it if we add some other *Type with more arguments. Also it will still be clear which type a value is (user will scan the definition and see NullaryType or whatever immediately instead of counting number of arguments.

$.Pair = typeWithURL(
  'sanctuary-def/Pair',
  BinaryType,
  function(x) { return $$typeEq('Array')(x) && x.length === 2; },
  function(pair) { return [pair[0]]; },
  function(pair) { return [pair[1]]; }
)
// vs
$.Pair = typeX(
  'sanctuary-def/Pair',
  function(x) { return $$typeEq('Array')(x) && x.length === 2; },
  function(pair) { return [pair[0]]; },
  function(pair) { return [pair[1]]; }
)

[davidchambers]

Great suggestion, Irakli! I was not at all happy with typeX. I've updated the pull request. :)

[safareli]

don't know what this 'A' and \u2660 are, but is it intentional?

[davidchambers]

'\u2660' is '♠'. Neither that nor 'A' belong where they are. I'm not sure how they came to be there, but we should remove them now that we're aware of the errors.

[safareli]

👍