Move name field from AssocItem to AssocKind variants.

To accurately reflect that RPITIT assoc items don't have a name. This avoids the use of `kw::Empty` to mean "no name", which is error prone. Helps with #137978.

Author: nnethercote

clippy_lints/src/assigning_clones.rs

@@ -111,8 +111,8 @@ impl<'tcx> LateLintPass<'tcx> for AssigningClones {
  // Only suggest if `clone_from`/`clone_into` is explicitly implemented
  && resolved_assoc_items.in_definition_order().any(|assoc|
  match which_trait {
- CloneTrait::Clone => assoc.name == sym::clone_from,
- CloneTrait::ToOwned => assoc.name.as_str() == "clone_into",
+ CloneTrait::Clone => assoc.name() == sym::clone_from,
+ CloneTrait::ToOwned => assoc.name().as_str() == "clone_into",
  }
  )
  && !clone_source_borrows_from_dest(cx, lhs, rhs.span)

clippy_lints/src/methods/double_ended_iterator_last.rs

@@ -24,7 +24,7 @@ pub(super) fn check(cx: &LateContext<'_>, expr: &'_ Expr<'_>, self_expr: &'_ Exp
  && let Ok(Some(fn_def)) = Instance::try_resolve(cx.tcx, cx.typing_env(), id, args)
  // find the provided definition of Iterator::last
  && let Some(item) = cx.tcx.get_diagnostic_item(sym::Iterator)
- && let Some(last_def) = cx.tcx.provided_trait_methods(item).find(|m| m.name.as_str() == "last")
+ && let Some(last_def) = cx.tcx.provided_trait_methods(item).find(|m| m.name().as_str() == "last")
  // if the resolved method is the same as the provided definition
  && fn_def.def_id() == last_def.def_id
  {

clippy_lints/src/missing_trait_methods.rs

@@ -81,7 +81,7 @@ impl<'tcx> LateLintPass<'tcx> for MissingTraitMethods {
  cx,
  MISSING_TRAIT_METHODS,
  cx.tcx.def_span(item.owner_id),
- format!("missing trait method provided by default: `{}`", assoc.name),
+ format!("missing trait method provided by default: `{}`", assoc.name()),
  |diag| {
  diag.span_help(cx.tcx.def_span(assoc.def_id), "implement the method");
  },

clippy_lints/src/same_name_method.rs

@@ -85,7 +85,7 @@ impl<'tcx> LateLintPass<'tcx> for SameNameMethod {
  .associated_items(did)
  .in_definition_order()
  .filter(|assoc_item| assoc_item.is_fn())
- .map(|assoc_item| assoc_item.name)
+ .map(|assoc_item| assoc_item.name())
  .collect()
  } else {
  BTreeSet::new()

clippy_lints/src/unconditional_recursion.rs

@@ -322,7 +322,7 @@ impl UnconditionalRecursion {
  .in_definition_order()
  // We're not interested in foreign implementations of the `Default` trait.
  .find(|item| {
- item.is_fn() && item.def_id.is_local() && item.name == kw::Default
+ item.is_fn() && item.def_id.is_local() && item.name() == kw::Default
  })
  && let Some(body_node) = cx.tcx.hir_get_if_local(assoc_item.def_id)
  && let Some(body_id) = body_node.body_id()