Haskell has type holes. There are plugins that give you code actions to complete them, split case, etc. I love type holes.
Agda has them too and they're more powerful there: https://agda.readthedocs.io/en/latest/language/lexical-struc...
Agda has them too and they're more powerful there: https://agda.readthedocs.io/en/latest/language/lexical-struc...
Super useful for when you don't know what are you missing and get a type signature for it.
It's mostly useful for when you declare some `const foo: (bar: Bar) => Whatever` and in the midst of your implementation you don't know what you're missing.
Requires an advanced level in TS to be used to the max.
https://gcanti.github.io/fp-ts/modules/function.ts.html#hole
https://effect-ts.github.io/effect/effect/Function.ts.html#h...
we (team hazel) recently used that device in our typescript version of a hazel setup for typed-hole-contextualized code completion as described in https://dl.acm.org/doi/10.1145/3689728
const transformFoo: (foos: Foo[]) => Bar
and you start implementing it and get stuck with some callback or whatever you can put a `hole` and it will tell you the type signature of what you're missing.
[1] - https://www.manning.com/books/type-driven-development-with-i...