Add more simple types

[andy-hanson]

PR checklist

• Addresses an existing issue: #0000
• New feature, bugfix, or enhancement
  • Includes tests
• Documentation update (Not needed)

What changes did you make?

Consider the undefined and never types to be simple types. This allows writing undefined[] or never[].
The second commit changes tests to prove that I changed something. Could be removed if you think it's ugly.

[rule-update] array-type now consider undefined and never as simple types, allowing undefined[] and never[]

[adidahiya]

lgtm, thanks @andy-hanson

[adidahiya]

Hmm, actually, this is a small breaking change because tslint would previously enforce using Array<T> for undefined and never. We should probably put this functionality behind an option and only make the breaking change in v5.0.

[andy-hanson]

I wouldn't mind waiting for version 5 to do this.

[ajafff]

What about ts.SyntaxKind.LiteralType?
That would allow for true[], 1337[], "foo"[].

I just want to add this to the discussion. I don't have an opinion wether they should be considered simple types or not.

[adidahiya]

yeah it's a subjective call about what is considered "simple" here. IMO the examples you just proposed are a little confusing to read (partially because literals in type positions are a more recent addition to the language), so I would prefer writing Array<true>, Array<1337>, Array<"foo">. open to criticism here though.