// assignment → identifier "=" assignment | logic_or ;
private Expr Assignment()
{
Expr expr = Or();
if (CheckCurrentToken(TokenType.Equal))
{
Token equalsToken = GetCurrentTokenAndAdvance();
Expr value = Assignment();
var nameToken = expr as VariableExpr;
if (nameToken != null)
{
return(new AssignExpr(nameToken.name, value));
}
else if (expr is GetExpr)
{
GetExpr get = (GetExpr)expr;
return(new SetExpr(get.obj, get.name, value));
}
CreateError(equalsToken, ErrorType.InvalidAssignmentTarget);
}
return(expr);
}
public Object Visit_GetExpr(GetExpr expr)
{
Object obj = Evaluate(expr.obj);
if (obj is LoxInstance)
{
return(((LoxInstance)obj).Get(expr.name));
}
throw new RuntimeException(expr.name.line, expr.name.column, "Only instances have properties.");
}
public object VisitGetExpr(GetExpr expr)
{
var obj = Evaluate(expr.Object) as LoxInstance;
if (obj == null)
{
throw new LoxRuntimeException(expr.Name, "Only instances have properties.");
}
return(obj.Get(expr.Name));
}
// Call -> Primary ( "(" Arguments? ")" )*
private AstNode Call()
{
AstNode expr = Primary();
while (true)
{
if (Match(TokenType.LEFT_PAREN))
{
expr = FinishCall(expr);
}
else if (Match(TokenType.DOT))
{
var name = Consume(TokenType.IDENTIFIER, "Expect property name after '.'.");
expr = new GetExpr(expr, name);
}
else
{
break;
}
}
return(expr);
}
private Expr Call()
{
Expr expr = Primary();
while (true)
{
if (CheckCurrentTokenAndAdvance(TokenType.LeftParen))
{
expr = FinishCall(expr);
}
else if (CheckCurrentTokenAndAdvance(TokenType.Dot))
{
Token name = Expect(TokenType.Identifier, ErrorType.ExpectedIdentifier);
expr = new GetExpr(expr, name);
}
else
{
break;
}
}
return(expr);
}
public object VisitGetExpr(GetExpr expr)
{
Resolve(expr.Object);
return(null);
}
public Void Visit_GetExpr(GetExpr expr)
{
Resolve(expr.obj);
return(null);
}
public string Visit_GetExpr(GetExpr expr)
{
var name = (string)expr.name.value;
return(Parenthesize("Get " + name, expr.obj));
}