private BoundExpression RewriteDeconstruction(
ArrayBuilder <Binder.DeconstructionVariable> lhsTargets,
Conversion conversion,
TypeSymbol leftType,
BoundExpression right,
bool isUsed)
{
if (right.Kind == BoundKind.ConditionalOperator)
{
var conditional = (BoundConditionalOperator)right;
Debug.Assert(!conditional.IsRef);
return(conditional.Update(
conditional.IsRef,
VisitExpression(conditional.Condition),
RewriteDeconstruction(lhsTargets, conversion, leftType, conditional.Consequence, isUsed: true),
RewriteDeconstruction(lhsTargets, conversion, leftType, conditional.Alternative, isUsed: true),
conditional.ConstantValue,
leftType));
}
var temps = ArrayBuilder <LocalSymbol> .GetInstance();
var effects = DeconstructionSideEffects.GetInstance();
BoundExpression returnValue = ApplyDeconstructionConversion(lhsTargets, right, conversion, temps, effects, isUsed, inInit: true);
effects.Consolidate();
if (!isUsed)
{
// When a deconstruction is not used, the last effect is used as return value
Debug.Assert(returnValue is null);
var last = effects.PopLast();
if (last is null)
{
temps.Free();
effects.Free();
// Deconstructions with no effects lower to nothing. For example, `(_, _) = (1, 2);`
return(null);
}
return(_factory.Sequence(temps.ToImmutableAndFree(), effects.ToImmutableAndFree(), last));
}
else
{
if (!returnValue.HasErrors)
{
returnValue = VisitExpression(returnValue);
}
return(_factory.Sequence(temps.ToImmutableAndFree(), effects.ToImmutableAndFree(), returnValue));
}
}
/// <summary>
/// The left represents a tree of L-values. The structure of right can be missing parts of the tree on the left.
/// The conversion holds nested conversisons and deconstruction information, which matches the tree from the left,
/// and it provides the information to fill in the missing parts of the tree from the right and convert it to
/// the tree from the left.
///
/// A bound sequence is returned which has different phases of side-effects:
/// - the initialization phase includes side-effects from the left, followed by evaluations of the right
/// - the deconstruction phase includes all the invocations of Deconstruct methods and tuple element accesses below a Deconstruct call
/// - the conversion phase
/// - the assignment phase
/// </summary>
private BoundExpression RewriteDeconstruction(BoundTupleExpression left, Conversion conversion, BoundExpression right)
{
var temps = ArrayBuilder <LocalSymbol> .GetInstance();
var effects = DeconstructionSideEffects.GetInstance();
ArrayBuilder <Binder.DeconstructionVariable> lhsTargets = GetAssignmentTargetsAndSideEffects(left, temps, effects.init);
BoundExpression returnTuple = ApplyDeconstructionConversion(lhsTargets, right, conversion, temps, effects, inInit: true);
if (!returnTuple.HasErrors)
{
returnTuple = VisitExpression(returnTuple);
}
BoundExpression result = _factory.Sequence(temps.ToImmutableAndFree(), effects.ToImmutableAndFree(), returnTuple);
Binder.DeconstructionVariable.FreeDeconstructionVariables(lhsTargets);
return(result);
}
/// <summary>
/// The left represents a tree of L-values. The structure of right can be missing parts of the tree on the left.
/// The conversion holds nested conversions and deconstruction information, which matches the tree from the left,
/// and it provides the information to fill in the missing parts of the tree from the right and convert it to
/// the tree from the left.
///
/// A bound sequence is returned which has different phases of side-effects:
/// - the initialization phase includes side-effects from the left, followed by evaluations of the right
/// - the deconstruction phase includes all the invocations of Deconstruct methods and tuple element accesses below a Deconstruct call
/// - the conversion phase
/// - the assignment phase
/// </summary>
private BoundExpression RewriteDeconstruction(BoundTupleExpression left, Conversion conversion, BoundExpression right, bool isUsed)
{
var temps = ArrayBuilder <LocalSymbol> .GetInstance();
var effects = DeconstructionSideEffects.GetInstance();
ArrayBuilder <Binder.DeconstructionVariable> lhsTargets = GetAssignmentTargetsAndSideEffects(left, temps, effects.init);
BoundExpression returnValue = ApplyDeconstructionConversion(lhsTargets, right, conversion, temps, effects, isUsed, inInit: true);
effects.Consolidate();
BoundExpression result;
if (!isUsed)
{
// When a deconstruction is not used, the last effect is used as return value
Debug.Assert(returnValue is null);
var last = effects.PopLast();
if (last is null)
{
// Deconstructions with no effects lower to nothing. For example, `(_, _) = (1, 2);`
result = null;
temps.Free();
_ = effects.ToImmutableAndFree();
}
else
{
result = _factory.Sequence(temps.ToImmutableAndFree(), effects.ToImmutableAndFree(), last);
}
}
else
{
if (!returnValue.HasErrors)
{
returnValue = VisitExpression(returnValue);
}
result = _factory.Sequence(temps.ToImmutableAndFree(), effects.ToImmutableAndFree(), returnValue);
}
Binder.DeconstructionVariable.FreeDeconstructionVariables(lhsTargets);
return(result);
}