public object visitThisExpr(Expr.This expr)
{
if (currentClass == ClassType.NONE)
{
Lox.error(expr.Keyword,
"Cannot use `this` outside of class");
return(null);
}
resolveLocal(expr, expr.Keyword);
return(null);
}
public object visitVariableExpr(Expr.Variable expr)
{
bool initialized;
if (scopes.Count > 0 && scopes.Peek().TryGetValue(expr.Name.Lexeme, out initialized) && initialized == false)
{
Lox.error(expr.Name, "Cannot read local variable in it's own initializer");
}
resolveLocal(expr, expr.Name);
return(null);
}
public object visitClassStmt(Stmt.Class stmt)
{
ClassType enclosingClass = currentClass;
currentClass = ClassType.CLASS;
declare(stmt.Name);
define(stmt.Name);
if (stmt.SuperClass != null &&
stmt.Name.Lexeme == stmt.SuperClass.Name.Lexeme)
{
Lox.error(stmt.SuperClass.Name,
"A class cannot inherit from itself");
}
if (stmt.SuperClass != null)
{
currentClass = ClassType.SUBCLASS;
resolve(stmt.SuperClass);
}
if (stmt.SuperClass != null)
{
beginScope();
scopes.Peek()["super"] = true;
}
beginScope();
scopes.Peek()["this"] = true;
foreach (Stmt.Function method in stmt.Methods)
{
FunctionType declaration = FunctionType.METHOD;
if (method.Name.Lexeme == "init")
{
declaration = FunctionType.INITIALIZER;
}
resolveFunction(method, declaration);
}
endScope();
if (stmt.SuperClass != null)
{
endScope();
}
currentClass = enclosingClass;
return(null);
}
private void declare(Token name)
{
if (scopes.Count == 0)
{
return;
}
var scope = scopes.Peek();
if (scope.ContainsKey(name.Lexeme))
{
Lox.error(name, "Variable with this name already delared in this scope");
}
scope[name.Lexeme] = false;
}
public object visitSuperExpr(Expr.Super expr)
{
if (currentClass == ClassType.NONE)
{
Lox.error(expr.Keyword,
"Cannot use 'super' outisde of class");
}
else if (currentClass != ClassType.SUBCLASS)
{
Lox.error(expr.Keyword,
"Cannot use 'super' in a class with no superclass");
}
resolveLocal(expr, expr.Keyword);
return(null);
}
public object visitReturnStmt(Stmt.Return stmt)
{
if (currentFunction == FunctionType.NONE)
{
Lox.error(stmt.Keyword, "Cannot return from top-level code");
}
if (stmt.Value != null)
{
if (currentFunction == FunctionType.INITIALIZER)
{
Lox.error(stmt.Keyword,
"Cannot return a value from initilizer;");
}
resolve(stmt.Value);
}
return(null);
}
private void scanString()
{
while (peek() != '"' && !isAtEnd())
{
if (peek() == '\n')
{
line++;
}
advance();
}
if (isAtEnd())
{
Lox.error(line, "Unterminated string");
return;
}
advance();
string value = Source.Substring(start + 1, current - start - 2);
addToken(TokenType.STRING, value);
}
private ParseError error(Token token, string message)
{
Lox.error(token, message);
synchronize();
return(new ParseError());
}
private void scanToken()
{
char c = advance();
switch (c)
{
case '(': addToken(TokenType.LEFT_PAREN); break;
case ')': addToken(TokenType.RIGHT_PAREN); break;
case '{': addToken(TokenType.LEFT_BRACE); break;
case '}': addToken(TokenType.RIGHT_BRACE); break;
case ',': addToken(TokenType.COMMA); break;
case '.': addToken(TokenType.DOT); break;
case '-': addToken(TokenType.MINUS); break;
case '+': addToken(TokenType.PLUS); break;
case ';': addToken(TokenType.SEMICOLON); break;
case '*': addToken(TokenType.STAR); break;
case '?': addToken(TokenType.QUEST); break;
case ':': addToken(TokenType.COLON); break;
case '!': addToken(match('=')? TokenType.BANG_EQUAL: TokenType.BANG); break;
case '=': addToken(match('=')? TokenType.EQUAL_EQUAL: TokenType.EQUAL); break;
case '<': addToken(match('=')? TokenType.LESS_EQUAL: TokenType.LESS); break;
case '>': addToken(match('=')? TokenType.GREATER_EQUAL: TokenType.GREATER); break;
case '/':
if (match('/'))
{
while (peek() != '\n' && !isAtEnd())
{
advance();
}
}
else
{
addToken(TokenType.SLASH);
}
break;
case ' ':
case '\r':
case '\t':
break;
case '\n':
line++;
break;
case '"': scanString(); break;
default:
if (isDigit(c))
{
scanNumber();
}
else if (isAlpha(c))
{
scanIdentifier();
}
else
{
Lox.error(line, $"Unexpected character '{c}'");
};
break;
}
}