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, 3 insertions, 3 deletions

diff --git a/compiler/rustc_attr_parsing/src/context.rs b/compiler/rustc_attr_parsing/src/context.rs
index 3bf03f84ce8..972614a3366 100644
--- a/compiler/rustc_attr_parsing/src/context.rs
+++ b/compiler/rustc_attr_parsing/src/context.rs
@@ -222,7 +222,7 @@ impl<'sess> AttributeParser<'sess> {
             // if we're only looking for a single attribute,
             // skip all the ones we don't care about
             if let Some(expected) = self.parse_only {
-                if attr.name_or_empty() != expected {
+                if !attr.has_name(expected) {
                     continue;
                 }
             }
@@ -232,7 +232,7 @@ impl<'sess> AttributeParser<'sess> {
             // that's expanded right? But no, sometimes, when parsing attributes on macros,
             // we already use the lowering logic and these are still there. So, when `omit_doc`
             // is set we *also* want to ignore these
-            if omit_doc == OmitDoc::Skip && attr.name_or_empty() == sym::doc {
+            if omit_doc == OmitDoc::Skip && attr.has_name(sym::doc) {
                 continue;
             }
 
@@ -250,7 +250,7 @@ impl<'sess> AttributeParser<'sess> {
                     }))
                 }
                 // // FIXME: make doc attributes go through a proper attribute parser
-                // ast::AttrKind::Normal(n) if n.name_or_empty() == sym::doc => {
+                // ast::AttrKind::Normal(n) if n.has_name(sym::doc) => {
                 //     let p = GenericMetaItemParser::from_attr(&n, self.dcx());
                 //
                 //     attributes.push(Attribute::Parsed(AttributeKind::DocComment {