[gcc r14-7819] gccrs: ast: Add manual dispatch for meta item downcasting

[Arthur Cohen <cohenarthur@gcc.gnu.org>]

https://gcc.gnu.org/g:5920e4b7579c664c17a07d126c7fb09f4d786849

commit r14-7819-g5920e4b7579c664c17a07d126c7fb09f4d786849
Author: Pierre-Emmanuel Patry <pierre-emmanuel.patry@embecosm.com>
Date:   Tue Jun 20 13:26:45 2023 +0200

    gccrs: ast: Add manual dispatch for meta item downcasting
    
    Several meta items shall be downcasted in various places, this commit
    introduces values to dispatch on.
    
    gcc/rust/ChangeLog:
    
            * ast/rust-ast.h (class MetaItem): Add MetaItem dispatch values.
            * ast/rust-expr.h: Add LitExpr and PathLit dispatch.
            * ast/rust-macro.h: Add remaining dispatch getters.
    
    Signed-off-by: Pierre-Emmanuel Patry <pierre-emmanuel.patry@embecosm.com>

Diff:
---
 gcc/rust/ast/rust-ast.h   | 26 ++++++++++++++++++++++++++
 gcc/rust/ast/rust-expr.h  | 10 ++++++++++
 gcc/rust/ast/rust-macro.h | 30 ++++++++++++++++++++++++++++++
 3 files changed, 66 insertions(+)

diff --git a/gcc/rust/ast/rust-ast.h b/gcc/rust/ast/rust-ast.h
index 7989bbe13c1..faf14fe722b 100644
--- a/gcc/rust/ast/rust-ast.h
+++ b/gcc/rust/ast/rust-ast.h
@@ -681,12 +681,20 @@ protected:
   virtual MetaItemInner *clone_meta_item_inner_impl () const = 0;
 
 public:
+  enum class Kind
+  {
+    LitExpr,
+    MetaItem,
+  };
+
   // Unique pointer custom clone function
   std::unique_ptr<MetaItemInner> clone_meta_item_inner () const
   {
     return std::unique_ptr<MetaItemInner> (clone_meta_item_inner_impl ());
   }
 
+  virtual Kind get_kind () = 0;
+
   virtual ~MetaItemInner ();
 
   virtual location_t get_locus () const = 0;
@@ -897,6 +905,24 @@ class AttrInputLiteral;
 // abstract base meta item class
 class MetaItem : public MetaItemInner
 {
+public:
+  enum class ItemKind
+  {
+    Path,
+    Word,
+    NameValueStr,
+    PathLit,
+    Seq,
+    ListPaths,
+    ListNameValueStr,
+  };
+
+  MetaItemInner::Kind get_kind () override
+  {
+    return MetaItemInner::Kind::MetaItem;
+  }
+
+  virtual ItemKind get_item_kind () const = 0;
 };
 
 // Forward decl - defined in rust-expr.h
diff --git a/gcc/rust/ast/rust-expr.h b/gcc/rust/ast/rust-expr.h
index 63c7d107961..b3aa41726c4 100644
--- a/gcc/rust/ast/rust-expr.h
+++ b/gcc/rust/ast/rust-expr.h
@@ -200,6 +200,11 @@ public:
 
   bool check_cfg_predicate (const Session &session) const override;
 
+  MetaItemInner::Kind get_kind () override
+  {
+    return MetaItemInner::Kind::LitExpr;
+  }
+
 protected:
   // Use covariance to implement clone function as returning this type
   MetaItemLitExpr *clone_meta_item_inner_impl () const override
@@ -228,6 +233,11 @@ public:
     return path.as_string () + " = " + lit.as_string ();
   }
 
+  MetaItem::ItemKind get_item_kind () const override
+  {
+    return MetaItem::ItemKind::PathLit;
+  }
+
   // There are two Locations in MetaItemPathLit (path and lit_expr),
   //  we have no idea use which of them, just simply return UNKNOWN_LOCATION
   //  now.
diff --git a/gcc/rust/ast/rust-macro.h b/gcc/rust/ast/rust-macro.h
index c63b480de61..db8cf1ef5d4 100644
--- a/gcc/rust/ast/rust-macro.h
+++ b/gcc/rust/ast/rust-macro.h
@@ -844,6 +844,11 @@ public:
 
   Attribute to_attribute () const override;
 
+  MetaItem::ItemKind get_item_kind () const override
+  {
+    return MetaItem::ItemKind::Path;
+  }
+
 protected:
   // Use covariance to implement clone function as returning this type
   MetaItemPath *clone_meta_item_inner_impl () const override
@@ -902,6 +907,11 @@ public:
 
   Attribute to_attribute () const override;
 
+  MetaItem::ItemKind get_item_kind () const override
+  {
+    return MetaItem::ItemKind::Seq;
+  }
+
 protected:
   // Use covariance to implement clone function as returning this type
   MetaItemSeq *clone_meta_item_inner_impl () const override
@@ -933,6 +943,11 @@ public:
 
   Attribute to_attribute () const override;
 
+  MetaItem::ItemKind get_item_kind () const override
+  {
+    return MetaItem::ItemKind::Word;
+  }
+
 protected:
   // Use covariance to implement clone function as returning this type
   MetaWord *clone_meta_item_inner_impl () const override
@@ -984,6 +999,11 @@ public:
 
   bool is_key_value_pair () const override { return true; }
 
+  MetaItem::ItemKind get_item_kind () const override
+  {
+    return MetaItem::ItemKind::NameValueStr;
+  }
+
 protected:
   // Use covariance to implement clone function as returning this type
   MetaNameValueStr *clone_meta_item_inner_impl () const override
@@ -1021,6 +1041,11 @@ public:
 
   Attribute to_attribute () const override;
 
+  MetaItem::ItemKind get_item_kind () const override
+  {
+    return MetaItem::ItemKind::ListPaths;
+  }
+
 private:
   bool check_path_exists_in_cfg (const Session &session,
 				 const SimplePath &path) const;
@@ -1061,6 +1086,11 @@ public:
 
   Attribute to_attribute () const override;
 
+  MetaItem::ItemKind get_item_kind () const override
+  {
+    return MetaItem::ItemKind::ListNameValueStr;
+  }
+
 protected:
   // Use covariance to implement clone function as returning this type
   MetaListNameValueStr *clone_meta_item_inner_impl () const override