Several generics default to `any` instead of their base type

[mootari]

Describe the bug, including details regarding any error messages, version, and platform.

Several Generics have any set as default value instead of defaulting to the type from which they extend, like the following example:

Field<T extends DataType = any>

Unfortunately this effectively removes all type guarantees when properties that inherit the type are passed down. Example (playground link):

import type {Field, DataType} from "apache-arrow";

"not a type" satisfies Field["type"]; // Does not error
"not a type" satisfies Field<DataType>["type"]; // Errors

The generics should instead define their base type as default type:

Field<T extends DataType = DataType>

[domoritz]

I guess the intention was not always specify the generic but then having a default is probably not right. So sounds like a good thing to change. Do you want to send a pull request?

[mootari]

but then having a default is probably not right

Having a default makes sense so that the types can be used in function parameters, but the default needs to match the type that the generic is supposed to extend from.

I can look into creating a PR (if no one beats me to it). Though considering the other TypeScript related issues that are floating around I have a suspicion that it might not be as straightforward as just replacing any with the base type.

[mootari]

@domoritz I'm having some difficulty understanding how I should verify any changes I might make. From what I can tell types are only checked at build time which makes it somewhat challenging to quickly gauge the impact of a change.

If I may, I would suggest that I first try to get rid of any lint and type errors so that it becomes possible to run tsc --noEmit in the root. Does that sound reasonable to you?

[domoritz]

There should be no lint or retype errors without your changes. Make sure you have the right versions etc.