private void LowerWhenClause(BoundWhenDecisionDagNode whenClause)
{
// This node is used even when there is no when clause, to record bindings. In the case that there
// is no when clause, whenClause.WhenExpression and whenClause.WhenFalse are null, and the syntax for this
// node is the case clause.
// We need to assign the pattern variables in the code where they are in scope, so we produce a branch
// to the section where they are in scope and evaluate the when clause there.
var whenTrue = (BoundLeafDecisionDagNode)whenClause.WhenTrue;
LabelSymbol labelToSectionScope = GetDagNodeLabel(whenClause);
// We need the section syntax to get the section builder from the map. Unfortunately this is a bit awkward
SyntaxNode sectionSyntax = whenClause.Syntax is SwitchLabelSyntax l ? l.Parent : whenClause.Syntax;
bool foundSectionBuilder = _switchArms.TryGetValue(sectionSyntax, out ArrayBuilder <BoundStatement> sectionBuilder);
Debug.Assert(foundSectionBuilder);
sectionBuilder.Add(_factory.Label(labelToSectionScope));
foreach (BoundPatternBinding binding in whenClause.Bindings)
{
BoundExpression left = _localRewriter.VisitExpression(binding.VariableAccess);
// Since a switch does not add variables to the enclosing scope, the pattern variables
// are locals even in a script and rewriting them should have no effect.
Debug.Assert(left.Kind == BoundKind.Local && left == binding.VariableAccess);
BoundExpression right = _tempAllocator.GetTemp(binding.TempContainingValue);
if (left != right)
{
sectionBuilder.Add(_factory.Assignment(left, right));
}
}
var whenFalse = whenClause.WhenFalse;
var trueLabel = GetDagNodeLabel(whenTrue);
if (whenClause.WhenExpression != null && whenClause.WhenExpression.ConstantValue != ConstantValue.True)
{
_factory.Syntax = whenClause.Syntax;
BoundStatement conditionalGoto = _factory.ConditionalGoto(_localRewriter.VisitExpression(whenClause.WhenExpression), trueLabel, jumpIfTrue: true);
// Only add instrumentation (such as a sequence point) if the node is not compiler-generated.
if (IsSwitchStatement && !whenClause.WhenExpression.WasCompilerGenerated && _localRewriter.Instrument)
{
conditionalGoto = _localRewriter._instrumenter.InstrumentSwitchWhenClauseConditionalGotoBody(whenClause.WhenExpression, conditionalGoto);
}
sectionBuilder.Add(conditionalGoto);
Debug.Assert(whenFalse != null);
// We hide the jump back into the decision dag, as it is not logically part of the when clause
BoundStatement jump = _factory.Goto(GetDagNodeLabel(whenFalse));
sectionBuilder.Add(IsSwitchStatement ? _factory.HiddenSequencePoint(jump) : jump);
}
else
{
Debug.Assert(whenFalse == null);
sectionBuilder.Add(_factory.Goto(trueLabel));
}
}
private void LowerWhenClause(BoundWhenDecisionDagNode whenClause)
{
// This node is used even when there is no when clause, to record bindings. In the case that there
// is no when clause, whenClause.WhenExpression and whenClause.WhenFalse are null, and the syntax for this
// node is the case clause.
// We need to assign the pattern variables in the code where they are in scope, so we produce a branch
// to the section where they are in scope and evaluate the when clause there.
var whenTrue = (BoundLeafDecisionDagNode)whenClause.WhenTrue;
LabelSymbol labelToSectionScope = GetDagNodeLabel(whenClause);
// We need the section syntax to get the section builder from the map. Unfortunately this is a bit awkward
SyntaxNode?sectionSyntax = whenClause.Syntax is SwitchLabelSyntax l ? l.Parent : whenClause.Syntax;
Debug.Assert(sectionSyntax is { });
