Add TypeAliasName to ensure all constants used as T.type_alias are in CamelCase

[Morriar]

This cop ensures all constants used as T.type_alias are using CamelCase:

# bad
FOO_OR_BAR = T.type_alias { T.any(Foo, Bar) }

# good
FooOrBar = T.type_alias { T.any(Foo, Bar) }

[Morriar]

Please skip the first commit as it belong to #93 🙏

[RyanBrushett]

I think this will pass happily if name is something like "HELLO"

Should we also check for name == name.capitalize?

[Morriar]

I think we want to allow such things no? Like for class names: SSH, HTTP?

[vinistock]

I think we'll have to compromise here. Typically, we'd expect only acronyms to be all upcase, like SSH and HTTP, but Hello should be camelcase. Rails uses an inflector initializer to define which words in your app are acronyms and can be all upcase and if they're not on the list it's always considered as camelcase.

For rubocop-sorbet that feels like too much complexity for type aliases - especially since it's not tied to Rails. I think we'll need to decide whether we prefer acronyms to be forced to be camelcase or allow folks to attach type aliases to all upcase words like HELLO. My vote goes to force all to be camelcase.

[RyanBrushett]

I hadn't thought about the acronym case, good shout @Morriar
FWIW: There's at least one type_alias in Core called ID which would be affected by this decision. Supporting rails-style acronym convention would be consistent with Rubocop, as Alex pointed out.
My vote goes to upcase. My 0.02 dollars.

[Morriar]

Here are a few ones that are legit, yet would be rejected by a stricter rule:

• ID
• GraphQLVariablesType
• ARObject
• StatsDTag

I'm not sure I want to force renaming those as they look good. What I really want to avoid is things like VALUE_TYPE. But I agree that in the current state this cop is too permissive and would allow TYPE.

Not sure what's the best, I'm happy to let the votes decide.

[vinistock]

That's fair, I agree with only marking names with underscores as offenses.

[KaanOzkan]

I think we should lean towards giving more flexibility to the devs since we can't perfectly know what's allowed. Underscore offence seems good enough.

[KaanOzkan]

lgtm after typo