/// <summary>
/// Constructs AST node from operator (root) and one or two operands.
/// In order for the node to be successfully created stacks must contain
/// an operator and, depending on the operator, one or two operands.
/// </summary>
/// <example>
/// The newly created subtree (operator and root and operands are children)
/// is then pushed into the operands stack. Example: in a*b+c before '+'
/// can be processed, a*b is turned into an subtree and pushed as an operand
/// to the operands stack. Then new subtree can be created with + at the root
/// and 'c' and 'a*b' as its child nodes.
/// </example>
/// <param name="context">Parsing context</param>
/// <returns>Parsing error of any</returns>
private ParseErrorType MakeNode(ParseContext context)
{
IOperator operatorNode = _operators.Pop();
IRValueNode rightOperand = this.SafeGetOperand();
if (rightOperand == null)
{
// Oddly, no operands
return(ParseErrorType.RightOperandExpected);
}
if (operatorNode.IsUnary)
{
operatorNode.AppendChild(rightOperand);
operatorNode.RightOperand = rightOperand;
}
else
{
IRValueNode leftOperand = this.SafeGetOperand();
if (leftOperand == null)
{
// Operand is missing in expression like x <- [].
// Operator on top of the stack is <- since [] was not
// successfully parsed. So we need to mark right operand
// as error token.
context.AddError(new ParseError(ParseErrorType.LeftOperandExpected, ErrorLocation.Token, GetIndexerOrFunctionErrorRange(context, operatorNode)));
return(ParseErrorType.LeftOperandExpected);
}
if (leftOperand.End <= operatorNode.Start && rightOperand.Start >= operatorNode.End)
{
operatorNode.LeftOperand = leftOperand;
operatorNode.RightOperand = rightOperand;
operatorNode.AppendChild(leftOperand);
operatorNode.AppendChild(rightOperand);
}
else
{
return(ParseErrorType.UnexpectedToken);
}
}
_operands.Push(operatorNode);
return(ParseErrorType.None);
}
private ParseErrorType HandleFunctionOrIndexer(IOperator operatorNode)
{
// Indexing or function call is performed on the topmost operand which
// generally should be a variable or a node that evaluates to it.
// However, we leave syntax check to separate code.
IRValueNode operand = this.SafeGetOperand();
if (operand == null)
{
// Oddly, no operand
return(ParseErrorType.IndentifierExpected);
}
operatorNode.LeftOperand = operand;
operatorNode.AppendChild(operand);
_operands.Push(operatorNode);
return(ParseErrorType.None);
}
private ParseErrorType HandleFunctionOrIndexer(IOperator operatorNode) {
// Indexing or function call is performed on the topmost operand which
// generally should be a variable or a node that evaluates to it.
// However, we leave syntax check to separate code.
IRValueNode operand = this.SafeGetOperand();
if (operand == null) {
// Oddly, no operand
return ParseErrorType.IndentifierExpected;
}
operatorNode.LeftOperand = operand;
operatorNode.AppendChild(operand);
_operands.Push(operatorNode);
return ParseErrorType.None;
}