Rollup merge of #119231 - aDotInTheVoid:PatKind-struct-bool-docs, r=compiler-errors

Clairify `ast::PatKind::Struct` presese of `..` by using an enum instead of a bool

The bool is mainly used for when a `..` is present, but it is also set on recovery to avoid errors. The doc comment not describes both of these cases.

See cee794ee98/compiler/rustc_parse/src/parser/pat.rs (L890-L897) for the only place this is constructed.

r? ``@compiler-errors``

src/patterns.rs

@@ -259,9 +259,15 @@ fn rewrite(&self, context: &RewriteContext<'_>, shape: Shape) -> Option<String>
                 None,
                 None,
             ),
-            PatKind::Struct(ref qself, ref path, ref fields, ellipsis) => {
-                rewrite_struct_pat(qself, path, fields, ellipsis, self.span, context, shape)
-            }
+            PatKind::Struct(ref qself, ref path, ref fields, rest) => rewrite_struct_pat(
+                qself,
+                path,
+                fields,
+                rest == ast::PatFieldsRest::Rest,
+                self.span,
+                context,
+                shape,
+            ),
             PatKind::MacCall(ref mac) => {
                 rewrite_macro(mac, None, context, shape, MacroPosition::Pat)
             }