lang: add E type argument to Result type alias

[mina86]

Considering that Result is included in Anchor’s prelude, it’s quite
annoying when one suddenly needs to use Result with a different error
than Anchor’s Error (i.e. use the symbol Result like the actual Rust
Result type).

Add E type argument to Anchar’s Result type-alias so that the symbol
can continue to be used like in any Rust code even when someone
imports Anchor’s prelude.

Specify E’s default value to Anchor’s Error so existing Anchor-based
code can continue using the alias as before.

[vercel]

@mina86 is attempting to deploy a commit to the coral-xyz Team on Vercel.

A member of the Team first needs to authorize it.

[acheroncrypto]

A pre-defined error type is preferred for libraries e.g. syn::Result and std::io::Result.

To me, having generic errors only makes sense if the project is:

• A generic error library like anyhow
• An application

[mina86]

The problem is that Anchor’s Result is in prelude and importing everything in prelude is recommended way to write Anchor programs (in fact some Anchor macros require it IIRC). The difference with syn::Result or std::io::Result is that if I do use std::io::Result I consciously chose to use io’s Result. If Anchor had no prelude, the current approach wouldn’t be an issue. Anchor’s prelude shadowing a standard library type is the issue.

[acheroncrypto]

Yeah, I generally agree with overriding the default Result by importing the prelude can be annoying but given the fix for when you want to return a different error type is easy enough(1 line of code), I don't currently think we need to support generic error types from Anchor's Result. Having a known error type can be useful.

[mina86]

I don’t understand what you mean by ‘having a known error type’. With my proposed change the error type would still be known.

[acheroncrypto]

By "having a known error type" I mean having Anchor's Error type when using Anchor's Result type.

[mina86]

When you write Result<T> you still have Anchor’s Error type. Nothing changes on that front.

[acheroncrypto]

I'm aware.