Parse unnamed fields and anonymous structs or unions

Anonymous structs or unions are only allowed in struct field
definitions.

Co-authored-by: carbotaniuman <41451839+carbotaniuman@users.noreply.github.com>

src/types.rs

@@ -819,6 +819,8 @@ fn rewrite(&self, context: &RewriteContext<'_>, shape: Shape) -> Option<String>
             ast::TyKind::Tup(ref items) => {
                 rewrite_tuple(context, items.iter(), self.span, shape, items.len() == 1)
             }
+            ast::TyKind::AnonStruct(_) => Some(context.snippet(self.span).to_owned()),
+            ast::TyKind::AnonUnion(_) => Some(context.snippet(self.span).to_owned()),
             ast::TyKind::Path(ref q_self, ref path) => {
                 rewrite_path(context, PathContext::Type, q_self, path, shape)
             }

tests/target/anonymous-types.rs

@@ -0,0 +1,19 @@
+// Test for issue 85480
+// Pretty print anonymous struct and union types
+
+// pp-exact
+// pretty-compare-only
+
+struct Foo {
+    _: union  {
+        _: struct  {
+            a: u8,
+            b: u16,
+        },
+        c: u32,
+    },
+    d: u64,
+    e: f32,
+}
+
+fn main() {}