derive(Debug): Add stub implementation.

gcc/rust/ChangeLog:

	* expand/rust-derive-debug.cc: New file.
	* expand/rust-derive-debug.h: New file.
	* Make-lang.in: Compile them.
	* expand/rust-derive.cc (DeriveVisitor::derive): Call into DeriveDebug.

gcc/testsuite/ChangeLog:

	* rust/compile/derive-debug1.rs: New test.
	* rust/compile/nr2/exclude: Exclude it.

1 files changed, 55 insertions, 0 deletions

diff --git a/gcc/rust/expand/rust-derive-debug.h b/gcc/rust/expand/rust-derive-debug.h
new file mode 100644
index 0000000..14af89e
--- /dev/null
+++ b/gcc/rust/expand/rust-derive-debug.h
@@ -0,0 +1,55 @@
+// Copyright (C) 2025 Free Software Foundation, Inc.
+
+// This file is part of GCC.
+
+// GCC is free software; you can redistribute it and/or modify it under
+// the terms of the GNU General Public License as published by the Free
+// Software Foundation; either version 3, or (at your option) any later
+// version.
+
+// GCC is distributed in the hope that it will be useful, but WITHOUT ANY
+// WARRANTY; without even the implied warranty of MERCHANTABILITY or
+// FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
+// for more details.
+
+// You should have received a copy of the GNU General Public License
+// along with GCC; see the file COPYING3.  If not see
+// <http://www.gnu.org/licenses/>.
+
+#ifndef RUST_DERIVE_DEBUG_H
+#define RUST_DERIVE_DEBUG_H
+
+#include "rust-derive.h"
+#include "rust-ast.h"
+
+namespace Rust {
+namespace AST {
+
+// This derive is currently incomplete and only generate a stub implementation
+// which does not do any debug formatting
+class DeriveDebug : DeriveVisitor
+{
+public:
+  DeriveDebug (location_t loc);
+
+  std::unique_ptr<Item> go (Item &);
+
+private:
+  std::unique_ptr<Item> expanded;
+
+  std::unique_ptr<AssociatedItem> stub_debug_fn ();
+
+  std::unique_ptr<Item> stub_derive_impl (
+    std::string name,
+    const std::vector<std::unique_ptr<GenericParam>> &type_generics);
+
+  virtual void visit_struct (StructStruct &struct_item) override;
+  virtual void visit_tuple (TupleStruct &tuple_item) override;
+  virtual void visit_enum (Enum &enum_item) override;
+  virtual void visit_union (Union &enum_item) override;
+};
+
+} // namespace AST
+} // namespace Rust
+
+#endif // ! RUST_DERIVE_DEBUG_H