/
InvocationExpander.cs
61 lines (53 loc) · 2.02 KB
/
InvocationExpander.cs
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using System.Linq;
using System.Linq.Expressions;
namespace Simple.Expressions
{
public class InvocationExpander : ExpressionVisitor
{
private readonly ParameterExpression _parameter;
private readonly Expression _expansion;
private readonly InvocationExpander _previous;
public static T Expand<T>(T expr)
where T : LambdaExpression
{
return (T)new InvocationExpander().Visit(expr);
}
public InvocationExpander()
{
}
public InvocationExpander(ParameterExpression parameter, Expression expansion, InvocationExpander previous)
{
_parameter = parameter;
_expansion = expansion;
_previous = previous;
}
protected override Expression VisitInvocation(InvocationExpression iv)
{
if (iv.Expression.NodeType == ExpressionType.Lambda)
{
LambdaExpression lambda = (LambdaExpression)iv.Expression;
return lambda
.Parameters
.Select((x, i) => new { Parameter = x, Expansion = iv.Arguments[i] })
// add to the stack of available parameters bindings (this class doubles as an immutable stack)
.Aggregate(this, (previous, pair) => new InvocationExpander(pair.Parameter, pair.Expansion, previous))
// visit the body of the lambda using an expander including the new parameter bindings
.Visit(lambda.Body);
}
return base.VisitInvocation(iv);
}
protected override Expression VisitParameter(ParameterExpression p)
{
InvocationExpander expander = this;
while (null != expander)
{
if (expander._parameter == p)
{
return base.Visit(expander._expansion);
}
expander = expander._previous;
}
return base.VisitParameter(p);
}
}
}