Add a recursion depth limit for #3987 with a consideration to use a switch statement or refactor the code to not use a large if-else chain

src/parser.hpp

@@ -120,6 +120,8 @@ struct AstFile {
 	bool         allow_type;
 	bool         in_when_statement;
 
+	isize        recursion_depth_else_if;
+
 	isize total_file_decl_count;
 	isize delayed_decl_count;
 	Slice<Ast *> decls;