Added Result class for error handling while parsing

examples/parser-test.sp

@@ -1 +1 @@
-1+2+3*5
+2+2*6+

src/Lexer.cpp

@@ -170,6 +170,9 @@ TokenStream Lexer::lex(const std::string& text)
             case ']':
                 result.push_back(Token::make_with_line({TT_Exclamation, loc}, current_line_text));
                 break;
+            case '\377':
+                result.push_back(Token(TT_EOF,loc));
+                return result;
             default:
                 Error::throw_error(loc, current_line_text, "unknown character");
             }

src/Parser.cpp

@@ -15,7 +15,9 @@ std::shared_ptr<Parser> Parser::new_parser(const TokenStream& tokens)
 std::shared_ptr<ASTNode> Parser::parse()
 {
     advance();
-    return expr();
+    auto result = expr();
+    if(result.is_error()) result.ethrow();
+    return result.get();
 }
 
 int Parser::advance()
@@ -28,45 +30,51 @@ int Parser::advance()
     return 1;
 }
 
-std::shared_ptr<NumberNode> Parser::factor()
+Result<ExprNode> Parser::factor()
 {
-    Token token = *current_token;
+    Token& token = *current_token;
 
     if (token.tk_type == TT_Number)
     {
         advance();
-        return std::make_shared<IntegerNode>(token.int_value);
+        return Ok<ExprNode>(new IntegerNode(token.int_value),&token);
     }
 
     if (token.tk_type == TT_Float)
     {
         advance();
-        return std::make_shared<FloatNode>(token.float_value);
-    }
+        return Ok<ExprNode>(new FloatNode(token.float_value),&token);
     }
     
-std::shared_ptr<ExprNode> Parser::term()
+    return Err<ExprNode>("expected a number",&token);
+}
+
+Result<ExprNode> Parser::term()
 {
-    std::shared_ptr<ExprNode> left = factor();
+    Result<ExprNode> left = factor();
+    if(left.is_error()) return left;
     while (current_token->tk_type == TT_Mul || current_token->tk_type == TT_Div)
     {
-        Token op = *current_token;
+        Token& op = *current_token;
         advance();
-        std::shared_ptr<ExprNode> right = factor();
-        left = std::make_shared<MulNode>(left, right, op.tk_type == TT_Mul ? '*' : '/');
+        Result<ExprNode> right = factor();
+        if(right.is_error()) return right;
+        left = Ok<ExprNode>(new MulNode(left.get(), right.get(), op.tk_type == TT_Mul ? '*' : '/'), &op);
     }
     return left;
 }
 
-std::shared_ptr<ExprNode> Parser::expr()
+Result<ExprNode> Parser::expr()
 {
-    std::shared_ptr<ExprNode> left = term();
+    Result<ExprNode> left = term();
+    if(left.is_error()) return left;
     while (current_token->tk_type == TT_Plus || current_token->tk_type == TT_Minus)
     {
-        Token op = *current_token;
+        Token& op = *current_token;
         advance();
-        std::shared_ptr<ExprNode> right = term();
-        left = std::make_shared<SumNode>(left, right, op.tk_type == TT_Plus ? '+' : '-');
+        Result<ExprNode> right = term();
+        if(right.is_error()) return right;
+        left = Ok<ExprNode>(new SumNode(left.get(), right.get(), op.tk_type == TT_Plus ? '+' : '-'),&op);
     }
     return left;
 }

src/Parser.h

@@ -3,6 +3,7 @@
 #include "AST/SumNode.h"
 #include "Error.h"
 #include "Lexer.h"
+#include "Result.h"
 #include "sapphirepch.h"
 
 /* Parser class for the Sapphire compiler. */
@@ -15,9 +16,9 @@ class Parser
     int advance();
     Token* current_token;
 
-    std::shared_ptr<NumberNode> factor();
-    std::shared_ptr<ExprNode> expr();
-    std::shared_ptr<ExprNode> term();
+    Result<ExprNode> factor();
+    Result<ExprNode> expr();
+    Result<ExprNode> term();
 
   public:
     /* Construct a new Parser with the given TokenStream. */

src/Result.h

@@ -9,27 +9,30 @@ class Result
 public:
   Result() = default;
   bool is_error() const { return m_is_error; }
-  void ethrow();
-  std::shared_ptr<T> get() { return m_result; }
+  void ethrow() { std::exit(1); }
+  std::shared_ptr<T> get() 
+  {
+    return m_result; 
+  }
 protected:
-  std::shared_ptr<Token> m_token;
+  Token* m_token;
   std::shared_ptr<T> m_result;
   bool m_is_error;
   std::string m_error;
   
-  Result(T* result, Token* token) : m_result(result), m_token(token) {}
-  Result(const std::string& error, Token* token) : m_error(std::move(error)), m_token(token) {}
+  Result(T* result, Token* token) : m_result(result), m_token(token), m_is_error(false) {}
+  Result(const std::string& error, Token* token) : m_error(std::move(error)), m_token(token), m_is_error(true) {}
 };
 
 template<typename T>
-class Ok : public Result<T>
+class Ok final : public Result<T>
 {
 public:
   Ok(T* result, Token* token) : Result<T>(result,token) {}
 };
 
 template<typename T>
-class Err : public Result<T>
+class Err final : public Result<T>
 {
 public:
   Err(const std::string& error, Token* token) : Result<T>(std::move(error),token) {}