/// <summary>
/// Reads a null coalescing expression.
/// </summary>
/// <param name="leftHandSide">The expression on the left hand side of the operator.</param>
/// <param name="previousPrecedence">The precedence of the expression just before this one.</param>
/// <param name="parentReference">The parent code unit.</param>
/// <param name="unsafeCode">Indicates whether the code being parsed resides in an unsafe code block.</param>
/// <returns>Returns the expression.</returns>
private NullCoalescingExpression GetNullCoalescingExpression(
Expression leftHandSide, ExpressionPrecedence previousPrecedence, Reference<ICodePart> parentReference, bool unsafeCode)
{
Param.AssertNotNull(leftHandSide, "leftHandSide");
Param.Ignore(previousPrecedence);
Param.AssertNotNull(parentReference, "parentReference");
Param.Ignore(unsafeCode);
NullCoalescingExpression expression = null;
var expressionReference = new Reference<ICodePart>();
// Read the details of the expression.
OperatorSymbol operatorToken = this.PeekOperatorToken(parentReference, expressionReference);
Debug.Assert(operatorToken.SymbolType == OperatorType.NullCoalescingSymbol, "Expected a null-coalescing symbol");
// Check the precedence of the operators to make sure we can gather this statement now.
ExpressionPrecedence precedence = GetOperatorPrecedence(operatorToken.SymbolType);
if (CheckPrecedence(previousPrecedence, precedence))
{
// Add the operator token to the document and advance the symbol manager up to it.
this.symbols.Advance();
this.tokens.Add(operatorToken);
// Get the expression on the right-hand side of the operator.
Expression rightHandSide = this.GetOperatorRightHandExpression(precedence, expressionReference, unsafeCode);
// Create the partial token list for the expression.
CsTokenList partialTokens = new CsTokenList(this.tokens, leftHandSide.Tokens.First, this.tokens.Last);
// Create and return the expression.
expression = new NullCoalescingExpression(partialTokens, leftHandSide, rightHandSide);
expressionReference.Target = expression;
}
return expression;
}
private NullCoalescingExpression GetNullCoalescingExpression(Expression leftHandSide, ExpressionPrecedence previousPrecedence, bool unsafeCode)
{
NullCoalescingExpression expression = null;
OperatorSymbol item = this.PeekOperatorToken();
ExpressionPrecedence operatorPrecedence = GetOperatorPrecedence(item.SymbolType);
if (CheckPrecedence(previousPrecedence, operatorPrecedence))
{
this.symbols.Advance();
this.tokens.Add(item);
Expression operatorRightHandExpression = this.GetOperatorRightHandExpression(operatorPrecedence, unsafeCode);
CsTokenList tokens = new CsTokenList(this.tokens, leftHandSide.Tokens.First, this.tokens.Last);
expression = new NullCoalescingExpression(tokens, leftHandSide, operatorRightHandExpression);
}
return expression;
}