private Expression GenerateIteratorStatement(VariablePath iteratorVariablePath,
Func<Expression> generateMoveNextUpdatePosition,
int iteratorTupleIndex,
LabeledStatementAst stmt,
Action<List<Expression>, Expression> generateBody)
{
// We convert:
// foreach ($x in $enumerable) {}
// Into:
// try
// {
// $oldforeach = $foreach
// $enumerable = condition
// $foreach = GetEnumerator $enumerable
// if ($foreach == $null && $enumerable != $null)
// {
// $foreach = (new object[] { $enumerable }).GetEnumerator()
// }
// if ($foreach != $null)
// {
// while ($foreach.MoveNext())
// {
// $x = $foreach.Current
// }
// }
// }
// finally
// {
// $foreach = $oldforeach
// }
// The translation for switch is similar.
var temps = new List<ParameterExpression>();
var exprs = new List<Expression>();
var avs = new AutomaticVarSaver(this, iteratorVariablePath, iteratorTupleIndex);
bool generatingForeach = stmt is ForEachStatementAst;
exprs.Add(avs.SaveAutomaticVar());
// $enumerable = condition
// $foreach/$switch = GetEnumerator $enumerable
var enumerable = NewTemp(typeof(object), "enumerable");
temps.Add(enumerable);
if (generatingForeach)
{
exprs.Add(UpdatePosition(stmt.Condition));
}
exprs.Add(
Expression.Assign(enumerable,
GetRangeEnumerator(stmt.Condition.GetPureExpression())
?? CaptureStatementResults(stmt.Condition, CaptureAstContext.Enumerable).Convert(typeof(object))));
var iteratorTemp = NewTemp(typeof(IEnumerator), iteratorVariablePath.UnqualifiedPath);
temps.Add(iteratorTemp);
exprs.Add(Expression.Assign(iteratorTemp,
DynamicExpression.Dynamic(PSEnumerableBinder.Get(), typeof(IEnumerator), enumerable)));
// In a foreach, generate:
// if ($foreach == $null && $enumerable != $null)
// {
// $foreach = (new object[] { $enumerable }).GetEnumerator()
// }
// In a switch, generate:
// if ($switch == $null)
// {
// $switch = (new object[] { $enumerable }).GetEnumerator()
// }
var testNeedScalarToEnumerable =
generatingForeach
? Expression.AndAlso(
Expression.Equal(iteratorTemp, ExpressionCache.NullConstant),
Expression.NotEqual(enumerable, ExpressionCache.NullConstant))
: Expression.Equal(iteratorTemp, ExpressionCache.NullConstant);
var scalarToEnumerable =
Expression.Assign(iteratorTemp,
Expression.Call(Expression.NewArrayInit(typeof(object),
Expression.Convert(enumerable, typeof(object))),
CachedReflectionInfo.IEnumerable_GetEnumerator));
exprs.Add(Expression.IfThen(testNeedScalarToEnumerable, scalarToEnumerable));
exprs.Add(avs.SetNewValue(iteratorTemp));
var moveNext = Expression.Block(
generateMoveNextUpdatePosition(),
Expression.Call(iteratorTemp, CachedReflectionInfo.IEnumerator_MoveNext));
var loop = GenerateWhileLoop(stmt.Label,
() => moveNext,
(loopBody, breakTarget, continueTarget) => generateBody(loopBody, Expression.Property(iteratorTemp, CachedReflectionInfo.IEnumerator_Current)));
// With a foreach, the enumerator may never get assigned, in which case we skip the loop entirely.
// Generate that test.
// With a switch, the switch body is never skipped, so skip generating that test, and skip creating
// target block.
if (generatingForeach)
{
exprs.Add(Expression.IfThen(Expression.NotEqual(iteratorTemp, ExpressionCache.NullConstant), loop));
}
else
{
exprs.Add(loop);
}
return Expression.Block(
temps.Concat(avs.GetTemps()),
Expression.TryFinally(Expression.Block(exprs), avs.RestoreAutomaticVar()));
}
private Expression GenerateIteratorStatement(VariablePath iteratorVariablePath, Func<Expression> generateMoveNextUpdatePosition, int iteratorTupleIndex, LabeledStatementAst stmt, Action<List<Expression>, Expression> generateBody)
{
List<ParameterExpression> first = new List<ParameterExpression>();
List<Expression> expressions = new List<Expression>();
AutomaticVarSaver saver = new AutomaticVarSaver(this, iteratorVariablePath, iteratorTupleIndex);
bool flag = stmt is ForEachStatementAst;
expressions.Add(saver.SaveAutomaticVar());
ParameterExpression item = this.NewTemp(typeof(object), "enumerable");
first.Add(item);
if (flag)
{
expressions.Add(this.UpdatePosition(stmt.Condition));
}
expressions.Add(Expression.Assign(item, this.GetRangeEnumerator(stmt.Condition.GetPureExpression()) ?? this.CaptureStatementResults(stmt.Condition, CaptureAstContext.Enumerable, null).Convert(typeof(object))));
ParameterExpression iteratorTemp = this.NewTemp(typeof(IEnumerator), iteratorVariablePath.UnqualifiedPath);
first.Add(iteratorTemp);
expressions.Add(Expression.Assign(iteratorTemp, Expression.Dynamic(PSEnumerableBinder.Get(), typeof(IEnumerator), item)));
BinaryExpression test = flag ? Expression.AndAlso(Expression.Equal(iteratorTemp, ExpressionCache.NullConstant), Expression.NotEqual(item, ExpressionCache.NullConstant)) : Expression.Equal(iteratorTemp, ExpressionCache.NullConstant);
BinaryExpression ifTrue = Expression.Assign(iteratorTemp, Expression.Call(Expression.NewArrayInit(typeof(object), new Expression[] { Expression.Convert(item, typeof(object)) }), CachedReflectionInfo.IEnumerable_GetEnumerator));
expressions.Add(Expression.IfThen(test, ifTrue));
expressions.Add(saver.SetNewValue(iteratorTemp));
BlockExpression moveNext = Expression.Block(generateMoveNextUpdatePosition(), Expression.Call(iteratorTemp, CachedReflectionInfo.IEnumerator_MoveNext));
Expression expression4 = this.GenerateWhileLoop(stmt.Label, () => moveNext, delegate (List<Expression> loopBody, LabelTarget breakTarget, LabelTarget continueTarget) {
generateBody(loopBody, Expression.Property(iteratorTemp, CachedReflectionInfo.IEnumerator_Current));
}, null);
if (flag)
{
expressions.Add(Expression.IfThen(Expression.NotEqual(iteratorTemp, ExpressionCache.NullConstant), expression4));
}
else
{
expressions.Add(expression4);
}
return Expression.Block(first.Concat<ParameterExpression>(saver.GetTemps()), new Expression[] { Expression.TryFinally(Expression.Block(expressions), saver.RestoreAutomaticVar()) });
}