public override void VisitIfExpression(BoundIfExpression node)
{
_writer.WriteKeyword("if ");
_writer.WritePunctuation("(");
node.Condition.Accept(this);
_writer.WritePunctuation(") ");
_writer.WriteLine();
WriteNestedExpression(node.Then);
_writer.WriteKeyword(" else ");
_writer.WriteLine();
WriteNestedExpression(node.Else);
}
protected override BoundExpression RewriteIfExpression(BoundIfExpression node)
{
/*
* if (<condition>)
* <thenBody>
* else
* <elseBody>
*
*
* to
*
* gotoIfFalse <condition> <elseLabel>
* <thenBody>
* goto <endLabel>
* <elseLabel>
* <elseBody>
* <endLabel>
*
*/
var token = GenerateLabelToken();
var elseLabel = GenerateLabel("IfElse", token);
var endLabel = GenerateLabel("IfEnd", token);
var variable = GenerateVariable(node.Type);
var condition = RewriteExpression(node.Condition);
if (condition is BoundLiteralExpression literal)
{
return(RewriteExpression((bool)literal.Value ? node.Then : node.Else));
}
var then = RewriteExpression(node.Then);
var @else = RewriteExpression(node.Else);
var variableExpression = new BoundVariableExpression(node.Syntax, variable);
var block = new BoundBlockExpression(
node.Syntax,
ImmutableArray.Create <BoundStatement>(
new BoundVariableDeclarationStatement(node.Syntax, variable, null),
new BoundConditionalGotoStatement(node.Syntax, elseLabel, condition),
new BoundAssignmentStatement(node.Syntax, variableExpression, then),
new BoundGotoStatement(node.Syntax, endLabel),
new BoundLabelStatement(node.Syntax, elseLabel),
new BoundAssignmentStatement(node.Syntax, variableExpression, @else),
new BoundLabelStatement(node.Syntax, endLabel)
),
variableExpression
);
return(RewriteExpression(block));
}
public virtual void VisitIfExpression(BoundIfExpression node) => this.DefaultVisit(node);
