Fix ICE in diagnostic_hir_wf_check

[FabianWolff]

Fixes #87495. The documentation for ObligationCauseCode::WellFormed says that

it is always correct [...] to specify WellFormed(None)

instead of WellFormed(Some(...)), which seems to have caused the issue here, as diagnostic_hir_wf_check does not expect to be called with an associated constant and will ICE:

rust/compiler/rustc_typeck/src/hir_wf_check.rs

Lines 131 to 134 in fd853c0

	hir::Node::TraitItem(item) => match item.kind {
	hir::TraitItemKind::Type(_, ty) => ty,
	ref item => bug!("Unexpected TraitItem {:?}", item),
	},

Therefore, I have changed check_associated_item() to pass a WellFormed(None) for associated constants.

r? @Aaron1011

[Aaron1011]

@FabianWolff: I think a better solution would be to add support for hir::TraitItemKind::Const. We can perform well-formed checking on the type of the const by using the first tuple field of TraitItemKind::Const (the &'hir Ty<'hir> field).

[FabianWolff]

@FabianWolff: I think a better solution would be to add support for hir::TraitItemKind::Const. We can perform well-formed checking on the type of the const by using the first tuple field of TraitItemKind::Const (the &'hir Ty<'hir> field).

Fixed. Thanks for the quick review!

[Aaron1011]

Thanks!
@bors r+

[bors]

📌 Commit dbd0fd2 has been approved by Aaron1011