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, 4 insertions, 4 deletions

diff --git a/compiler/rustc_expand/src/base.rs b/compiler/rustc_expand/src/base.rs
index 49f6d58172f..f5eaf7d616b 100644
--- a/compiler/rustc_expand/src/base.rs
+++ b/compiler/rustc_expand/src/base.rs
@@ -824,10 +824,10 @@ impl SyntaxExtension {
             return Err(item.span);
         }
 
-        match item.name_or_empty() {
-            sym::no => Ok(CollapseMacroDebuginfo::No),
-            sym::external => Ok(CollapseMacroDebuginfo::External),
-            sym::yes => Ok(CollapseMacroDebuginfo::Yes),
+        match item.name() {
+            Some(sym::no) => Ok(CollapseMacroDebuginfo::No),
+            Some(sym::external) => Ok(CollapseMacroDebuginfo::External),
+            Some(sym::yes) => Ok(CollapseMacroDebuginfo::Yes),
             _ => Err(item.path.span),
         }
     }