Move `has_self` field to `hir::AssocKind::Fn`.

`hir::AssocItem` currently has a boolean `fn_has_self_parameter` field,
which is misplaced, because it's only relevant for associated fns, not
for associated consts or types. This commit moves it (and renames it) to
the `AssocKind::Fn` variant, where it belongs.

This requires introducing a new C-style enum, `AssocTag`, which is like
`AssocKind` but without the fields. This is because `AssocKind` values
are passed to various functions like `find_by_ident_and_kind` to
indicate what kind of associated item should be searched for, and having
to specify `has_self` isn't relevant there.

New methods:
- Predicates `AssocItem::is_fn` and `AssocItem::is_method`.
- `AssocItem::as_tag` which converts `AssocItem::kind` to `AssocTag`.

Removed `find_by_name_and_kinds`, which is unused.

`AssocItem::descr` can now distinguish between methods and associated
functions, which slightly improves some error messages.

1 files changed, 6 insertions, 6 deletions

diff --git a/src/librustdoc/clean/inline.rs b/src/librustdoc/clean/inline.rs
index 3a2b6974681..2f6870e3c36 100644
--- a/src/librustdoc/clean/inline.rs
+++ b/src/librustdoc/clean/inline.rs
@@ -490,17 +490,17 @@ pub(crate) fn build_impl(
                         return true;
                     }
                     if let Some(associated_trait) = associated_trait {
-                        let assoc_kind = match item.kind {
-                            hir::ImplItemKind::Const(..) => ty::AssocKind::Const,
-                            hir::ImplItemKind::Fn(..) => ty::AssocKind::Fn,
-                            hir::ImplItemKind::Type(..) => ty::AssocKind::Type,
+                        let assoc_tag = match item.kind {
+                            hir::ImplItemKind::Const(..) => ty::AssocTag::Const,
+                            hir::ImplItemKind::Fn(..) => ty::AssocTag::Fn,
+                            hir::ImplItemKind::Type(..) => ty::AssocTag::Type,
                         };
                         let trait_item = tcx
                             .associated_items(associated_trait.def_id)
                             .find_by_ident_and_kind(
                                 tcx,
                                 item.ident,
-                                assoc_kind,
+                                assoc_tag,
                                 associated_trait.def_id,
                             )
                             .unwrap(); // SAFETY: For all impl items there exists trait item that has the same name.
@@ -527,7 +527,7 @@ pub(crate) fn build_impl(
                             .find_by_ident_and_kind(
                                 tcx,
                                 item.ident(tcx),
-                                item.kind,
+                                item.as_tag(),
                                 associated_trait.def_id,
                             )
                             .unwrap(); // corresponding associated item has to exist