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.

3 files changed, 4 insertions, 6 deletions

diff --git a/compiler/rustc_incremental/messages.ftl b/compiler/rustc_incremental/messages.ftl
index 2a65101d360..bbc1fab05df 100644
--- a/compiler/rustc_incremental/messages.ftl
+++ b/compiler/rustc_incremental/messages.ftl
@@ -93,7 +93,7 @@ incremental_undefined_clean_dirty_assertions =
 incremental_undefined_clean_dirty_assertions_item =
     clean/dirty auto-assertions not yet defined for Node::Item.node={$kind}
 
-incremental_unknown_item = unknown item `{$name}`
+incremental_unknown_rustc_clean_argument = unknown `rustc_clean` argument
 
 incremental_unrecognized_depnode = unrecognized `DepNode` variant: {$name}
 
diff --git a/compiler/rustc_incremental/src/errors.rs b/compiler/rustc_incremental/src/errors.rs
index b4a207386dc..dbc72d085be 100644
--- a/compiler/rustc_incremental/src/errors.rs
+++ b/compiler/rustc_incremental/src/errors.rs
@@ -107,11 +107,10 @@ pub(crate) struct NotLoaded<'a> {
 }
 
 #[derive(Diagnostic)]
-#[diag(incremental_unknown_item)]
-pub(crate) struct UnknownItem {
+#[diag(incremental_unknown_rustc_clean_argument)]
+pub(crate) struct UnknownRustcCleanArgument {
     #[primary_span]
     pub span: Span,
-    pub name: Symbol,
 }
 
 #[derive(Diagnostic)]
diff --git a/compiler/rustc_incremental/src/persist/dirty_clean.rs b/compiler/rustc_incremental/src/persist/dirty_clean.rs
index d40a0d514f6..64166255fa4 100644
--- a/compiler/rustc_incremental/src/persist/dirty_clean.rs
+++ b/compiler/rustc_incremental/src/persist/dirty_clean.rs
@@ -405,8 +405,7 @@ fn check_config(tcx: TyCtxt<'_>, attr: &Attribute) -> bool {
             debug!("check_config: searching for cfg {:?}", value);
             cfg = Some(config.contains(&(value, None)));
         } else if !(item.has_name(EXCEPT) || item.has_name(LOADED_FROM_DISK)) {
-            tcx.dcx()
-                .emit_err(errors::UnknownItem { span: attr.span(), name: item.name_or_empty() });
+            tcx.dcx().emit_err(errors::UnknownRustcCleanArgument { span: item.span() });
         }
     }