I'm not familiar with state of the art for language servers but here's common IntelliJ refactors I use across Go and TypeScript (and Java a while ago):

- Add a parameter to a method signature and fill it in with a default value.

- Reorder method parameters.

- Extract a block of code to a method that infers the correct input and output types.

The most advanced refactoring I've done with IntelliJ is structural replace for Java which can do something like: for every private method matching the name "*DoThing" defined on a class that extends Foo, insert a log line at the beginning of the method: https://www.jetbrains.com/help/idea/structural-search-and-re...

I make heavy use of the "integrated" aspect of IntelliJ. One of the nicer benefits is that SQL strings are type-checked against a database schema.