Replace infallible `name_or_empty` methods with fallible `name` methods.

I'm removing empty identifiers everywhere, because in practice they
always mean "no identifier" rather than "empty identifier". (An empty
identifier is impossible.) It's better to use `Option` to mean "no
identifier" because you then can't forget about the "no identifier"
possibility.

Some specifics:
- When testing an attribute for a single name, the commit uses the
  `has_name` method.
- When testing an attribute for multiple names, the commit uses the new
  `has_any_name` method.
- When using `match` on an attribute, the match arms now have `Some` on
  them.

In the tests, we now avoid printing empty identifiers by not printing
the identifier in the `error:` line at all, instead letting the carets
point out the problem.

1 files changed, 2 insertions, 3 deletions

diff --git a/compiler/rustc_ast_passes/src/ast_validation.rs b/compiler/rustc_ast_passes/src/ast_validation.rs
index dc77e7b2834..daf8ff5dc65 100644
--- a/compiler/rustc_ast_passes/src/ast_validation.rs
+++ b/compiler/rustc_ast_passes/src/ast_validation.rs
@@ -347,7 +347,7 @@ impl<'a> AstValidator<'a> {
                     sym::forbid,
                     sym::warn,
                 ];
-                !arr.contains(&attr.name_or_empty()) && rustc_attr_parsing::is_builtin_attr(*attr)
+                !attr.has_any_name(&arr) && rustc_attr_parsing::is_builtin_attr(*attr)
             })
             .for_each(|attr| {
                 if attr.is_doc_comment() {
@@ -945,8 +945,7 @@ impl<'a> Visitor<'a> for AstValidator<'a> {
                 self.visit_attrs_vis_ident(&item.attrs, &item.vis, ident);
                 self.check_defaultness(item.span, *defaultness);
 
-                let is_intrinsic =
-                    item.attrs.iter().any(|a| a.name_or_empty() == sym::rustc_intrinsic);
+                let is_intrinsic = item.attrs.iter().any(|a| a.has_name(sym::rustc_intrinsic));
                 if body.is_none() && !is_intrinsic {
                     self.dcx().emit_err(errors::FnWithoutBody {
                         span: item.span,