Remove Path::is_ident.

It checks that a path has a single segment that matches the given
symbol, and that there are zero generic arguments. It has a single use.

We also have `impl PartialEq<Symbol> for Path` which does exactly the
same thing *except* it doesn't check for zero generic arguments, which
seems like an oversight. It has numerous uses.

This commit removes `Path::is_ident`, adds a test for zero generic
arguments to `PartialEq<Symbol> for Path`, and changes the single use of
`is_ident` to instead use `==`.

compiler/rustc_ast/src/ast.rs

@@ -99,8 +99,15 @@ pub struct Path {
 
 impl PartialEq<Symbol> for Path {
     #[inline]
-    fn eq(&self, symbol: &Symbol) -> bool {
-        matches!(&self.segments[..], [segment] if segment.ident.name == *symbol)
+    fn eq(&self, name: &Symbol) -> bool {
+        if let [segment] = self.segments.as_ref()
+            && segment.args.is_none()
+            && segment.ident.name == *name
+        {
+            true
+        } else {
+            false
+        }
     }
 }
 
@@ -120,17 +127,6 @@ impl Path {
         Path { segments: thin_vec![PathSegment::from_ident(ident)], span: ident.span, tokens: None }
     }
 
-    pub fn is_ident(&self, name: Symbol) -> bool {
-        if let [segment] = self.segments.as_ref()
-            && segment.args.is_none()
-            && segment.ident.name == name
-        {
-            true
-        } else {
-            false
-        }
-    }
-
     pub fn is_global(&self) -> bool {
         self.segments.first().is_some_and(|segment| segment.ident.name == kw::PathRoot)
     }