[kt] Kotlin 1.4 support: minimally fun interfaces appear broken

[kevin1e100]

Kotlin 1.4 introduces a few features that may affect parsing/syntax highlighting, notably:

• fun interface declarations: these currently look broken, apparently because codemirror expects a function declaration after the fun keyword. Instead, fun should be treated as a modifier here (while leaving function declarations unchanged).
• trailing commas affect function declarations and invocations, but seem to already be tolerated/handled
• type annotations may affect parsing of types, including function types, e.g., fun foo(init: @Bar Baz.(@Bar Foo)->String): @Bar String

[mtaran-google]

@marijnh do you think you would be able to help with this?

[marijnh]

Sure. Attached patch adds support for fun interface (as I understand it from your explanation, not being a Kotlin programmer myself). The grammar seems to already allow annotations in front of types. If that doesn't cover your 3rd point, please elaborate.

[kevin1e100]

The fun interface patch looks right to me: fun immediately precedes interface for this case, IIUC, and there can be modifiers incl. annotations preceding, e.g., @Foo public @Bar fun interface Baz.

Agree that type annotations appear to be working: I get the expected highlighting using them in functions, type parameters, and type arguments.

Thanks so much for your quick help with this!