/// <summary>
/// Reduces the expression node to a simpler expression.
/// </summary>
/// <returns>The reduced expression.</returns>
public override Expression Reduce()
{
if (IsLifted)
{
if (Helpers.IsAlwaysNull(Operand))
{
return(Expression.Default(Type));
}
if (Helpers.IsNeverNull(Operand))
{
// CONSIDER: Peek into Operand and try to extract non-null value.
return
(Expression.Convert(
MakeFromEnd(Helpers.MakeNullableGetValueOrDefault(Operand)),
Type
));
}
if (Operand is ParameterExpression i)
{
return(MakeLiftedFromEnd(i));
}
else
{
var temp = Expression.Parameter(Operand.Type, "__t");
return
(Expression.Block(
new[] { temp },
Expression.Assign(temp, Operand),
MakeLiftedFromEnd(temp)
));
}
}
else
{
return(MakeFromEnd(Operand));
}
Expression MakeLiftedFromEnd(ParameterExpression operand) =>
Expression.Condition(
Helpers.MakeNullableHasValue(operand),
Expression.Convert(
MakeFromEnd(Helpers.MakeNullableGetValueOrDefault(operand)),
Type
),
Expression.Default(Type)
);
Expression MakeFromEnd(Expression operand)
{
var method = Method ?? FromEnd;
switch (method)
{
case MethodInfo m:
switch (m.GetParametersCached().Length)
{
case 1:
return(Expression.Call(m, operand));
case 2:
return(Expression.Call(m, operand, Expression.Constant(true)));
}
break;
case ConstructorInfo c:
switch (c.GetParametersCached().Length)
{
case 1:
return(Expression.New(c, operand));
case 2:
return(Expression.New(c, operand, Expression.Constant(true)));
}
break;
}
throw ContractUtils.Unreachable;
}
}