Rollup merge of rust-lang#102143 - Rageking8:fix-101540, r=TaKO8Ki

Recover from struct nested in struct Fixes rust-lang#101540 r? `@TaKO8Ki` Not sure If I have done it right.

Author: fee1-dead

compiler/rustc_parse/src/parser/item.rs

@@ -1715,6 +1715,7 @@ impl<'a> Parser<'a> {
  fn parse_field_ident(&mut self, adt_ty: &str, lo: Span) -> PResult<'a, Ident> {
  let (ident, is_raw) = self.ident_or_err()?;
  if !is_raw && ident.is_reserved() {
+ let snapshot = self.create_snapshot_for_diagnostic();
  let err = if self.check_fn_front_matter(false) {
  let inherited_vis = Visibility {
  span: rustc_span::DUMMY_SP,
@@ -1735,6 +1736,22 @@ impl<'a> Parser<'a> {
  err.help("unlike in C++, Java, and C#, functions are declared in `impl` blocks");
  err.help("see https://doc.rust-lang.org/book/ch05-03-method-syntax.html for more information");
  err
+ } else if self.eat_keyword(kw::Struct) {
+ match self.parse_item_struct() {
+ Ok((ident, _)) => {
+ let mut err = self.struct_span_err(
+ lo.with_hi(ident.span.hi()),
+ &format!("structs are not allowed in {adt_ty} definitions"),
+ );
+ err.help("consider creating a new `struct` definition instead of nesting");
+ err
+ }
+ Err(err) => {
+ err.cancel();
+ self.restore_snapshot(snapshot);
+ self.expected_ident_found()
+ }
+ }
  } else {
  self.expected_ident_found()
  };

src/test/ui/parser/issues/issue-101540.rs

@@ -0,0 +1,7 @@
+struct S1 {
+ struct S2 {
+ //~^ ERROR structs are not allowed in struct definitions
+ }
+}
+
+fn main() {}

src/test/ui/parser/issues/issue-101540.stderr

@@ -0,0 +1,10 @@
+error: structs are not allowed in struct definitions
+ --> $DIR/issue-101540.rs:2:5
+ |
+LL | struct S2 {
+ | ^^^^^^^^^
+ |
+ = help: consider creating a new `struct` definition instead of nesting
+
+error: aborting due to previous error
+