Implementing `From` for `sqlparser::ast::Statement` variants

[LucaCappelletti94]

The enum Statement has several variants of the type Variant(VariantStruct), such as Set(Set) or CreateIndex(CreateIndex).

I would like to implement the From<Variant> for Statement trait for all such variants of Statement.

Do let me know whether that would be desirable.

[LucaCappelletti94]

@iffyio could you kindly lmk your opinion on the matter before I start a PR?

[iffyio]

hmm I'm not sure this would necessarily be desirable, thinking since such an impl would have to be a TryFrom and would be error prone given in most cases, all except one option of statement would be valid for a given conversion. My thought is that the increased API surface might not be worth it if this isn't a very popular thing folks are looking to do.

[LucaCappelletti94]

I am not sure I understood why it would be a TryFrom - It is my understanding that it would be a From as it is always possible to convert a CreateTable into a Statement::CreateTable(CreateTable).

[iffyio]

Oh my bad, I read the intent as wanting to implement From<Statement> for CreateTable, For the opposite direction From<CreateTable> for Statement I think that would be reasonable yeah

[LucaCappelletti94]

Yeah, it would clean up all of the cases were we currently wrap X into Statement::X(X). Should I proceed then?

[iffyio]

Yeah I think we can make the change

[LucaCappelletti94]

Ok, I will get started once #2026 is merged, since the code changed there would also be involved in this refactoring.