[WIP] mgca: Add ConstArg representation for const items

[camelid]

r? @BoxyUwU

[bors]

☔ The latest upstream changes (presumably #141343) made this pull request unmergeable. Please resolve the merge conflicts.

[BoxyUwU]

@oli-obk I've assigned you to this PR alongside me because I'd definitely want you to review it before it lands since its so CTFE involved 🤔 I don't think it needs reviewing rn though, things are so up in the air and we're not bootstrapping yet :3

[BoxyUwU]

I don't know why find_attr! works here but tcx.has_attr(sym::type_const) doesnt. cc @jdonszelmann does has_attr work with new style attributes?

[BoxyUwU]

https://doc.rust-lang.org/stable/nightly-rustc/src/rustc_hir/hir.rs.html#1283 seems like no new style attributes don't work with has_attr if it's been parsed

[BoxyUwU]

it works sometimes though because we added has_attr calls in some places to fix ICEs which worked.

edit: ah no it probably just made that code unreachable lmao

[BoxyUwU]

Suggested change

	pub body: Option<ConstItemRhs>,
	pub rhs: Option<ConstItemRhs>,

body terminology doesn't make too much sense since it's only sometimes a body

[BoxyUwU]

This is now done, uncertain whether we may want some kind of ast validator or hir visitor to assert this :3

[rust-log-analyzer]

The job pr-check-2 failed! Check out the build log: (web) (plain enhanced) (plain)

Click to see the possible cause of the failure (guessed by this bot)

[RUSTC-TIMING] askama test:false 0.180
error[E0308]: mismatched types
    --> src/librustdoc/clean/mod.rs:1205:39
     |
1205 |                     kind: clean_const(default, Some(local_did), cx),
     |                           ----------- ^^^^^^^ expected `&ConstArg<'_>`, found `ConstItemRhs<'_>`
     |                           |
     |                           arguments to this function are incorrect
     |
     = note: expected reference `&rustc_hir::ConstArg<'_>`
                     found enum `rustc_hir::ConstItemRhs<'_>`
note: function defined here
    --> src/librustdoc/clean/mod.rs:309:15
     |
 309 | pub(crate) fn clean_const<'tcx>(
     |               ^^^^^^^^^^^
 310 |     constant: &hir::ConstArg<'tcx>,
     |     ------------------------------

error[E0308]: mismatched types
    --> src/librustdoc/clean/mod.rs:1255:35
     |
1255 |                 kind: clean_const(expr, Some(local_did), cx),
     |                       ----------- ^^^^ expected `&ConstArg<'_>`, found `ConstItemRhs<'_>`
     |                       |
     |                       arguments to this function are incorrect
     |
     = note: expected reference `&rustc_hir::ConstArg<'_>`
                     found enum `rustc_hir::ConstItemRhs<'_>`
note: function defined here
    --> src/librustdoc/clean/mod.rs:309:15
     |
 309 | pub(crate) fn clean_const<'tcx>(
     |               ^^^^^^^^^^^
 310 |     constant: &hir::ConstArg<'tcx>,
     |     ------------------------------

error[E0308]: mismatched types
    --> src/librustdoc/clean/mod.rs:2800:35
     |
2800 |                 kind: clean_const(body, Some(def_id), cx),
     |                       ----------- ^^^^ expected `&ConstArg<'_>`, found `ConstItemRhs<'_>`
     |                       |
     |                       arguments to this function are incorrect
     |
     = note: expected reference `&rustc_hir::ConstArg<'_>`
                     found enum `rustc_hir::ConstItemRhs<'_>`
note: function defined here
    --> src/librustdoc/clean/mod.rs:309:15
     |
 309 | pub(crate) fn clean_const<'tcx>(
     |               ^^^^^^^^^^^
 310 |     constant: &hir::ConstArg<'tcx>,
     |     ------------------------------

error[E0004]: non-exhaustive patterns: `&ConstArgKind::Error(_, _)` not covered
   --> src/librustdoc/clean/mod.rs:315:11
    |
315 |     match &constant.kind {
    |           ^^^^^^^^^^^^^^ pattern `&ConstArgKind::Error(_, _)` not covered
    |
note: `ConstArgKind<'_>` defined here
   --> /checkout/compiler/rustc_hir/src/hir.rs:500:1
    |
500 | pub enum ConstArgKind<'hir, Unambig = ()> {
    | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
...
509 |     Error(Span, ErrorGuaranteed),
    |     ----- not covered
    = note: the matched value is of type `&ConstArgKind<'_>`
help: ensure that all possible cases are being handled by adding a match arm with a wildcard pattern or an explicit pattern as shown
    |
326 ~         hir::ConstArgKind::Infer(..) => ConstantKind::Infer,
327 ~         &ConstArgKind::Error(_, _) => todo!(),
    |

error[E0004]: non-exhaustive patterns: `ConstArgKind::Error(_, _)` not covered
    --> src/librustdoc/clean/mod.rs:1810:32
     |
1810 |             let length = match const_arg.kind {
     |                                ^^^^^^^^^^^^^^ pattern `ConstArgKind::Error(_, _)` not covered
     |
note: `ConstArgKind<'_>` defined here
    --> /checkout/compiler/rustc_hir/src/hir.rs:500:1
     |
 500 | pub enum ConstArgKind<'hir, Unambig = ()> {
     | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
...
 509 |     Error(Span, ErrorGuaranteed),
     |     ----- not covered
     = note: the matched value is of type `ConstArgKind<'_>`