Parser.h

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#pragma once
#include "AST/NumberNode.h"
#include "Error.h"
#include "Lexer.h"
#include "sapphirepch.h"
 
/* Parser class for the Sapphire compiler. */
class Parser
{
    /* Struct to store a parsing result which can be either a parsing error or a success, in which case it contains a
     * pointer to the result. */
    template<typename T> struct ErrorOr
    {
        /* Return the stored pointer. */
        std::shared_ptr<T> get()
        {
            assert(!m_is_error);
            return m_ptr;
        }
 
        /* Call Error::throw_error() with the stored error's location, line text, and the error string provided to this
         * struct instance. */
        void ethrow()
        {
            assert(m_is_error);
            Error::throw_error(error_tok->loc, error_tok->line(), m_error);
        }
 
        /* Construct a new successful ErrorOr with a heap-allocated pointer to the result class. */
        ErrorOr(T* ptr) : m_ptr(ptr), m_is_error(false)
        {
        }
        /* Construct a new failed ErrorOr with the error details and the token where parsing failed. */
        ErrorOr(const std::string& error, const Token& error_tok)
            : m_error(error), m_is_error(true), error_tok(error_tok)
        {
        }
 
        /* Is this ErrorOr instance successful or failed? */
        bool is_error()
        {
            return m_is_error;
        }
 
      private:
        bool m_is_error;
        std::string m_error;
        std::unique_ptr<Token> error_tok;
        std::shared_ptr<T> m_ptr;
    };
 
  private:
    Parser(const TokenStream& tokens);
    TokenStream tokens;
 
    ErrorOr<ExprNode> walk_expr();
    ErrorOr<NumberNode> walk_number();
 
    int m_index;
    int saved_m_index;
 
    void save_current_position();
    void restore_current_position();
 
  public:
    ~Parser();
 
    /* Construct a new Parser with the given TokenStream. */
    static std::shared_ptr<Parser> new_parser(const TokenStream& tokens);
    /* Parse the stored TokenStream and return the top-level node of the result Abstract Syntax Tree. */
    std::shared_ptr<ASTNode> parse();
};