public override BoundNode VisitNullCoalescingAssignmentOperator(BoundNullCoalescingAssignmentOperator node)
{
if (_inExpressionLambda)
{
Error(ErrorCode.ERR_ExpressionTreeCantContainNullCoalescingAssignment, node);
}
return(base.VisitNullCoalescingAssignmentOperator(node));
}
public override BoundNode VisitNullCoalescingAssignmentOperator(BoundNullCoalescingAssignmentOperator node)
{
SyntaxNode syntax = node.Syntax;
var temps = ArrayBuilder <LocalSymbol> .GetInstance();
var stores = ArrayBuilder <BoundExpression> .GetInstance();
// Rewrite LHS with temporaries to prevent double-evaluation of side effects, as we'll need to use it multiple times.
BoundExpression transformedLHS = TransformCompoundAssignmentLHS(node.LeftOperand, stores, temps);
var lhsRead = MakeRValue(transformedLHS);
BoundExpression loweredRight = VisitExpression(node.RightOperand);
// Now that LHS is transformed with temporaries, we rewrite this node into a coalesce expression:
// lhsRead ?? (transformedLHS = loweredRight)
// transformedLHS = loweredRight
// isCompoundAssignment is only used for dynamic scenarios, and we want those scenarios to treat this like a standard assignment.
// See CodeGenNullCoalescingAssignmentTests.CoalescingAssignment_DynamicRuntimeCastFailure, which will fail if
// isCompoundAssignment is set to true. It will fail to throw a runtime binder cast exception.
BoundExpression assignment = MakeAssignmentOperator(syntax, transformedLHS, loweredRight, node.LeftOperand.Type, used: true, isChecked: false, isCompoundAssignment: false);
// lhsRead ?? (transformedLHS = loweredRight)
BoundExpression conditionalExpression = MakeNullCoalescingOperator(syntax, lhsRead, assignment, Conversion.Identity, BoundNullCoalescingOperatorResultKind.LeftType, node.LeftOperand.Type);
BoundExpression result = (temps.Count == 0 && stores.Count == 0) ?
conditionalExpression :
new BoundSequence(
syntax,
temps.ToImmutable(),
stores.ToImmutable(),
conditionalExpression,
conditionalExpression.Type);
temps.Free();
stores.Free();
return(result);
}
