Add section on record puns and type synonyms for records

[milesfrain]

No description provided.

[thomashoneyman]

This is covered later in this documentation, but I suppose it's information worth stating right away. Why not stick with the existing example in this section, though?

It is common to use type synonyms to for records via the type keyword:

type Author = { name :: String, interests :: Array String }

author :: Author
author = { name: "Phil", interests: ["Functional Programming", "JavaScript"] }

[milesfrain]

I wanted to define Point, since it's used in later examples.

[thomashoneyman]

I like this section, but there's some overlap with the language syntax documentation:
https://github.com/purescript/documentation/blob/837ec4ff3a956cdeda31997bf5f697ee738295b6/language/Syntax.md#additional-forms-with-records

I think we should merge that content into this file and then update the language syntax file to link here. It makes more sense for that content to be in this section and just a link be in that file.

[thomashoneyman]

I think that file has good content and it could be used to inform what you've written here.

[milesfrain]

there's some overlap with the language syntax

I'm not seeing any "Record Pun" examples in Syntax.md, but I agree that there are duplicated themes across Records.md, Syntax,md, and Pattern-Matching.md.

Whether this should be reorganized seems like a bigger discussion. Maybe something to tackle as part of #344

So for now, I'm thinking we should hold-off on making changes across multiple files.

[thomashoneyman]

As a side note, I think the Kinds section in here could use a little extra clarity. Specifically, I'm thinking of something like:

---

{ ... } is syntactic sugar for the Record type constructor. This type constructor is parameterized by a row of types:

-- these types are equivalent
type Language = { language :: String }
type Language' = Record ( language :: String )

A Record is constructed from a row type and represents a product type in which all fields in the row type are present. Using kind notation, Record has the kind # Type -> Type -- that is, it takes a row of types and produces a type.

Because ( language :: String ) denotes a row of types (and therefore has the kind # Type), it can be passed to the Record constructor or to the { ... } syntax for Record to construct a type:

type LanguageRow = ( language :: String ) -- has kind # Type

-- these are equivalent
type Language = Record LanguageRow
type Language' = { | LanguageRow }

[milesfrain]

Applied all suggestions except for moving content from Syntax.md to Records.md. I think that would still be good to do as a separate PR. Opened #368 to follow-up.

[JordanMartinez]

This PR hasn't been merged because this is likely useful, but has a few additions that are undesirable / repetitive