/// <summary>
/// Creates a new expression that is like this one, but using the supplied children. If all of the children are the same, it will return this expression.
/// </summary>
/// <param name="breakLabel">The <see cref="LoopCSharpStatement.BreakLabel" /> property of the result.</param>
/// <param name="continueLabel">The <see cref="LoopCSharpStatement.ContinueLabel" /> property of the result.</param>
/// <param name="test">The <see cref="ConditionalLoopCSharpStatement.Test" /> property of the result.</param>
/// <param name="body">The <see cref="LoopCSharpStatement.Body" /> property of the result.</param>
/// <returns>This expression if no children changed, or an expression with the updated children.</returns>
public WhileCSharpStatement Update(LabelTarget breakLabel, LabelTarget continueLabel, Expression test, Expression body)
{
if (breakLabel == this.BreakLabel && continueLabel == this.ContinueLabel && test == this.Test && body == this.Body)
{
return(this);
}
return(CSharpExpression.While(test, body, breakLabel, continueLabel));
}
/// <summary>
/// Creates a new expression that is like this one, but using the supplied children. If all of the children are the same, it will return this expression.
/// </summary>
/// <param name="breakLabel">The <see cref="LoopCSharpStatement.BreakLabel" /> property of the result.</param>
/// <param name="continueLabel">The <see cref="LoopCSharpStatement.ContinueLabel" /> property of the result.</param>
/// <param name="test">The <see cref="ConditionalLoopCSharpStatement.Test" /> property of the result.</param>
/// <param name="body">The <see cref="LoopCSharpStatement.Body" /> property of the result.</param>
/// <param name="locals">The <see cref="ConditionalLoopCSharpStatement.Locals" /> property of the result.</param>
/// <returns>This expression if no children changed, or an expression with the updated children.</returns>
public WhileCSharpStatement Update(LabelTarget breakLabel, LabelTarget continueLabel, Expression test, Expression body, IEnumerable <ParameterExpression> locals)
{
if (breakLabel == BreakLabel && continueLabel == ContinueLabel && test == Test && body == Body && SameElements(ref locals, Locals))
{
return(this);
}
return(CSharpExpression.While(test, body, breakLabel, continueLabel, locals));
}
protected override Expression ReduceCore()
{
var getEnumerator = Expression.Call(Collection, _getEnumerator);
var enumeratorType = getEnumerator.Type;
var enumeratorVariable = Expression.Parameter(enumeratorType, "__enumerator");
var moveNext = Expression.Call(enumeratorVariable, _moveNext);
var current = (Expression)Expression.Property(enumeratorVariable, _current);
if (Conversion != null)
{
current = Expression.Invoke(Conversion, current);
}
var cleanup = (Expression)Expression.Empty();
if (typeof(IDisposable).IsAssignableFrom(enumeratorType))
{
if (enumeratorType.IsValueType)
{
// NB: C# spec section 8.8.4 specifies a case for E being a nullable value type;
// however, it seems this case can't occur because the check for the foreach
// pattern would fail if E is a nullable value type (no Current property).
// Double-check this.
Debug.Assert(!enumeratorType.IsNullableType());
var dispose = enumeratorType.FindDisposeMethod();
cleanup = Expression.Call(enumeratorVariable, dispose);
}
else
{
var dispose = enumeratorType.FindDisposeMethod();
cleanup =
Expression.IfThen(
Expression.ReferenceNotEqual(enumeratorVariable, Expression.Constant(null, typeof(IDisposable))),
Expression.Call(enumeratorVariable, dispose)
);
}
}
else if (!enumeratorType.IsSealed)
{
var d = Expression.Parameter(typeof(IDisposable), "__disposable");
cleanup =
Expression.Block(
new[] { d },
Expression.Assign(d, Expression.TypeAs(enumeratorVariable, typeof(IDisposable))),
Expression.IfThen(
Expression.ReferenceNotEqual(d, Expression.Constant(null, typeof(IDisposable))),
Expression.Call(d, typeof(IDisposable).GetMethod("Dispose"))
)
);
}
var res =
Expression.Block(
new[] { enumeratorVariable },
Expression.Assign(enumeratorVariable, getEnumerator),
Expression.TryFinally(
CSharpExpression.While(
moveNext,
// NB: This is using C# 5.0 scoping rules for the loop variable.
Expression.Block(
new[] { Variable },
Expression.Assign(Variable, current),
Body
),
BreakLabel,
ContinueLabel
),
cleanup
)
);
return(res);
}
