gccrs: ast: Add new Kind enums for more precise downcasting

This commit adds things like Item::Kind, Expr::Kind, etc, and implements the associated `get_*_kind` functions.
It also removes the more generic AST::Kind enum we were using, which was incomplete and painful to use.

gcc/rust/ChangeLog:

	* ast/rust-ast.h: Add new Kind enums, remove Node class.
	* ast/rust-builtin-ast-nodes.h: Use new Kind enums.
	* ast/rust-expr.h (class LoopLabel): Likewise.
	* ast/rust-item.h: Likewise.
	* ast/rust-macro.h: Likewise.
	* ast/rust-path.h: Likewise.
	* expand/rust-macro-builtins-helpers.cc: Likewise.
	* expand/rust-macro-builtins-utility.cc (MacroBuiltin::concat_handler): Likewise.
	(MacroBuiltin::stringify_handler): Likewise.
	* resolve/rust-ast-resolve-expr.cc (ResolveExpr::visit): Likewise.
	* resolve/rust-early-name-resolver.cc: Likewise.
	* hir/rust-ast-lower.cc (ASTLoweringBlock::visit): Likewise.

1 files changed, 10 insertions, 0 deletions

diff --git a/gcc/rust/ast/rust-path.h b/gcc/rust/ast/rust-path.h
index 4e26b2f..b7eba44 100644
--- a/gcc/rust/ast/rust-path.h
+++ b/gcc/rust/ast/rust-path.h
@@ -850,6 +850,11 @@ public:
 
   Pattern::Kind get_pattern_kind () override { return Pattern::Kind::Path; }
 
+  Expr::Kind get_expr_kind () const override
+  {
+    return Expr::Kind::PathInExpression;
+  }
+
 protected:
   PathInExpression (std::vector<Attribute> &&outer_attrs,
 		    bool has_opening_scope_resolution, location_t locus,
@@ -1516,6 +1521,11 @@ public:
     rust_unreachable ();
   }
 
+  Expr::Kind get_expr_kind () const override
+  {
+    return Expr::Kind::QualifiedPathInExpression;
+  }
+
 protected:
   /* Use covariance to implement clone function as returning this object
    * rather than base */