`-Ztrait-solver=next`: add remaining builtin impl candidates

[lcnr]

see #107374 for which candidates are missing. It should be Destruct and Transmute

How to add a new builtin candidate

see #107282 as a reference.

to figure out how your builtin impl should work, you can take the old impl as a reference.
Using DiscriminantKind as an example the old solver deals with builtin candidates in the following places:

• assembly
  

  rust/compiler/rustc_trait_selection/src/traits/select/candidate_assembly.rs

  Lines 76 to 78 in 6874f4e

  	} else if lang_items.discriminant_kind_trait() == Some(def_id) {
  	// `DiscriminantKind` is automatically implemented for every type.
  	candidates.vec.push(BuiltinCandidate { has_nested: false });

• trait confirmation
  

  rust/compiler/rustc_trait_selection/src/traits/select/confirmation.rs

  Line 233 in 6874f4e

  fn confirm_builtin_candidate(

• project is_eligible check
  

  rust/compiler/rustc_trait_selection/src/traits/project.rs

  Line 1588 in 6874f4e

  if lang_items.discriminant_kind_trait() == Some(poly_trait_ref.def_id()) {

• project confirmation
  

  rust/compiler/rustc_trait_selection/src/traits/project.rs

  Lines 1928 to 1933 in 6874f4e

  	let (term, obligations) = if lang_items.discriminant_kind_trait() == Some(trait_def_id) {
  	let discriminant_def_id = tcx.require_lang_item(LangItem::Discriminant, None);
  	assert_eq!(discriminant_def_id, item_def_id);
  	(self_ty.discriminant_ty(tcx).into(), Vec::new())
  	} else if lang_items.pointee_trait() == Some(trait_def_id) {

Further help

In case you want to work on this and would like further help or are stuck, feel free to open a thread in https://rust-lang.zulipchat.com/#narrow/stream/364551-t-types.2Ftrait-system-refactor or pm me directly on zulip if that's more comfortable for you.

[detrumi]

@rustbot claim

[ndrewxie]

I'd like to try - I'll take a more detailed look tomorrow to see which parts detrumi finished already and which parts remain.
No guarantees I'll succeed but hey

@rustbot claim

[lcnr]

@ndrewxie i think this issue has sadly already been resolved 😅 🤔

Destruct has been implemented in #109495 and @compiler-errors has recently opened a PR for Transmute #110126