/// <summary>
/// Builds an expression for the given <paramref name="target"/>.
/// </summary>
/// <param name="target">The target whose expression is to be built.</param>
/// <param name="context">The compilation context.</param>
/// <param name="compiler">The expression compiler to be used to build any other expressions for targets
/// which might be required by the <paramref name="target" />. Note that unlike on the interface, where this
/// parameter is optional, this will always be provided</param>
protected override Expression Build(ExpressionTarget target, IExpressionCompileContext context, IExpressionCompiler compiler)
{
// reasonably simple - get the underlying expression, push it through the ExpressionTranslator to perform any parameter augmentations
// or conversion to other targets (like ResolvedTarget, CconstructorTarget etc) and then push the result through a
// TargetExpressionRewriter to compile any newly created targets into their respective expressions and into the resulting
// expression.
var translator = new ExpressionTranslator(context);
var translated = translator.Visit(target.ExpressionFactory != null ? target.ExpressionFactory(context) : target.Expression);
// the translator does lots of things - including identifying common code constructs which have rich target equivalents - such as
// the NewExpression being the same as the ConstructorTarget. When it creates a target in place of an expression, it wrap it
// inside a TargetExpression - so these then have to be compiled again via the TargetExpressionRewriter.
var targetRewriter = new TargetExpressionRewriter(compiler, context);
return(targetRewriter.Visit(translated));
}