Add function signature hooks for dataclasses functions: replace, asdict, astuple

[ilevkivskyi]

Currently, the plugin only supports dataclass creation (i.e. generation of dunder methods with correct types, including __init__). However, some functions in the dataclass modules have quite broad types in typeshed, for example:

def replace(obj: _T, **changes: Any) -> _T: ...

so that arbitrary arguments can be give for changes, etc. The plugin should be able to give more precise type for these functions. In particular, asdict could return a TypedDict.

[danr]

How would one go about to fix the type signature for replace? In TypeScript it is possible to give a replace function this type:

function replace<X extends Record<string, any>>(base: X, changes: Partial<X>): X {
  return {...base, ...changes}
}

It's not a 100% correspondence, I'm using TS' Record type instead of dataclass and just one single changes argument instead of a **changes keyword argument. But in essence it's the type I want to give replace from the dataclasses module.

[edaqa-uncountable]

This hole is allowing errors to leak through in some of my production code. Lacking a 'typeof' operator as well, it's difficult to ensure the types are correct.