feat(eslint-plugin): add prefer-function-type rule

[uniqueiniquity]

Add rule equivalent to TSLint's 'callable-types'.

[bradzacher]

@armano2 / @JamesHenry - why do we "support" implements on interfaces?

Typescript errors out if you try it?
https://www.typescriptlang.org/play/#src=interface%20Bar%20%7B%0D%0A%0D%0A%7D%0D%0A%0D%0Ainterface%20Foo%20implements%20Bar%20%7B%0D%0A%20%20%0D%0A%7D

[armano2]

we errors on them to, if user sets errorOnTypeScriptSyntacticAndSemanticIssues but right now we are outputting ast with "invalid" nodes to, this should not be handled in this rule, and it should be ignored during linting

[armano2]

you can find a little more info here: #185 (comment)

[armano2]

if we are going to be able to get semantic errors in "cheap" way without creating program, i'm going to cleanup AST from all invalid nodes, right now prettier expects that we are going to output ast as is, and they can rebuild it without changing functionality only style

[j-f1]

Should this have a different name? Perhaps prefer-function-type?

[uniqueiniquity]

@j-f1 I'm open for naming suggestions. I was just matching TSLint's name, since I don't have a good sense of the ESLint rule naming conventions

[bradzacher]

(hint: we don't really have any solid naming conventions yet 😅 )

[JamesHenry]

LGTM, but now that it's been pointed out, I agree the name could be a lot clearer

[bradzacher]

Code LGMT - change the name and we're good to go

[JamesHenry]

Apologies for the conflicts, we decided to remove the counts from the ROADMAP here: #225

They are too awkward to maintain manually, so this is the last time you will have to deal with syncing that up!

[JamesHenry]

Awesome, thanks!

[codecov]

Codecov Report

Merging #222 into master will increase coverage by 0.04%.
The diff coverage is 100%.

@@            Coverage Diff             @@
##           master     #222      +/-   ##
==========================================
+ Coverage   96.79%   96.83%   +0.04%     
==========================================
  Files          56       57       +1     
  Lines        2525     2558      +33     
  Branches      374      374              
==========================================
+ Hits         2444     2477      +33     
  Misses         42       42              
  Partials       39       39

Impacted Files	Coverage Δ
...es/eslint-plugin/lib/rules/prefer-function-type.js	100% <100%> (ø)