public void FreeVariableFinder_Basics()
{
var finder = new FreeVariableFinder();
var x = Expression.Parameter(typeof(int));
var y = Expression.Parameter(typeof(int));
var z = Expression.Parameter(typeof(int));
var ex = Expression.Parameter(typeof(Exception));
var e =
Expression.Block(
new[] { x },
Expression.Lambda(
Expression.TryCatch(
Expression.Add(x, y),
Expression.Catch(
ex,
z
)
),
y
)
);
finder.Visit(e);
CollectionAssert.AreEquivalent(new[] { z }, finder.FreeVariables.ToArray());
}
/// <summary>
/// Removes the variable used for a catch block if it's not used.
/// </summary>
/// <param name="catchBlock">The catch block to remove unused exception variables from.</param>
/// <returns>The result of rewriting the catch block.</returns>
private static CatchBlock RemoveUnusedVariables(CatchBlock catchBlock)
{
var variable = catchBlock.Variable;
if (variable != null)
{
// REVIEW: This does a lot of repeated scanning of the same child nodes.
// We could consider storing these results for later reuse.
var finder = new FreeVariableFinder();
finder.Visit(catchBlock.Filter);
finder.Visit(catchBlock.Body);
var freeVariables = finder.FreeVariables;
if (!freeVariables.Contains(variable))
{
return(catchBlock.Update(variable: null, catchBlock.Filter, catchBlock.Body));
}
}
return(catchBlock);
}