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+// 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_CMP_COMMON_H
+#define RUST_DERIVE_CMP_COMMON_H
+
+#include "rust-ast.h"
+#include "rust-ast-builder.h"
+#include "rust-item.h"
+#include "rust-path.h"
+
+namespace Rust {
+namespace AST {
+
+/**
+ * A pair of two expressions from each instance being compared. E.g. this
+ * could be `self.0` and `other.0`, or `self.field` and `other.field`
+ */
+struct SelfOther
+{
+  std::unique_ptr<Expr> self_expr;
+  std::unique_ptr<Expr> other_expr;
+
+  /* Create a <self.i> and an <other.i> expression */
+  static SelfOther index (Builder builder, int idx);
+  static std::vector<SelfOther> indexes (Builder builder,
+					 const std::vector<TupleField> &fields);
+
+  /* Create a <self.field> and an <other.field> expression */
+  static SelfOther field (Builder builder, const std::string &field_name);
+  static std::vector<SelfOther> fields (Builder builder,
+					const std::vector<StructField> &fields);
+};
+
+/**
+ * Builder for common match cases used when comparing two enum instances. This
+ * builder takes care of creating the unique patterns for the `self` instance
+ * and `other` instance, as well as the entire `MatchCase` required for building
+ * a proper comparision expression for an implementation of a comparision trait
+ * for an enum type. The functions take a lambda to use when creating the
+ * expression of the generated `MatchCase`.
+ */
+class EnumMatchBuilder
+{
+public:
+  /**
+   * The type of functions to call when creating the resulting expression in the
+   * generated `MatchCase`
+   */
+  using ExprFn
+    = std::function<std::unique_ptr<Expr> (std::vector<SelfOther> &&)>;
+
+  EnumMatchBuilder (const std::string &enum_path,
+		    const std::string &variant_path, ExprFn fn,
+		    Builder &builder)
+    : enum_path (enum_path), variant_path (variant_path), fn (fn),
+      builder (builder)
+  {}
+
+  /**
+   * Generate a `MatchCase` for an enum tuple variant
+   *
+   * (&Enum::Tuple(self0, self1), &Enum::Tuple(other0, other1)) => <fn>
+   */
+  MatchCase tuple (EnumItem &variant);
+
+  /**
+   * Generate a `MatchCase` for an enum struct variant
+   *
+   * (&Enum::Struct { a: self_a }, &Enum::Struct { a: other_a }) => <fn>
+   */
+  MatchCase strukt (EnumItem &variant);
+
+private:
+  const std::string &enum_path;
+  const std::string &variant_path;
+  ExprFn fn;
+  Builder &builder;
+};
+
+} // namespace AST
+} // namespace Rust
+
+#endif // ! RUST_DERIVE_CMP_COMMON_H