private BoundExpression LowerSwitchExpression(BoundSwitchExpression node)
{
_factory.Syntax = node.Syntax;
var result = ArrayBuilder <BoundStatement> .GetInstance();
var outerVariables = ArrayBuilder <LocalSymbol> .GetInstance();
var loweredSwitchGoverningExpression = _localRewriter.VisitExpression(node.Expression);
BoundDecisionDag decisionDag = ShareTempsIfPossibleAndEvaluateInput(
node.DecisionDag, loweredSwitchGoverningExpression, result, out BoundExpression savedInputExpression);
Debug.Assert(savedInputExpression != null);
// lower the decision dag.
(ImmutableArray <BoundStatement> loweredDag, ImmutableDictionary <SyntaxNode, ImmutableArray <BoundStatement> > switchSections) =
LowerDecisionDag(decisionDag);
// then add the rest of the lowered dag that references that input
result.Add(_factory.Block(loweredDag));
// A branch to the default label when no switch case matches is included in the
// decision tree, so the code in result is unreachable at this point.
// Lower each switch expression arm
LocalSymbol resultTemp = _factory.SynthesizedLocal(node.Type, node.Syntax, kind: SynthesizedLocalKind.SwitchCasePatternMatching);
LabelSymbol afterSwitchExpression = _factory.GenerateLabel("afterSwitchExpression");
foreach (BoundSwitchExpressionArm arm in node.SwitchArms)
{
_factory.Syntax = arm.Syntax;
var sectionBuilder = ArrayBuilder <BoundStatement> .GetInstance();
sectionBuilder.AddRange(switchSections[arm.Syntax]);
sectionBuilder.Add(_factory.Label(arm.Label));
sectionBuilder.Add(_factory.Assignment(_factory.Local(resultTemp), _localRewriter.VisitExpression(arm.Value)));
sectionBuilder.Add(_factory.Goto(afterSwitchExpression));
var statements = sectionBuilder.ToImmutableAndFree();
if (arm.Locals.IsEmpty)
{
result.Add(_factory.StatementList(statements));
}
else
{
// Lifetime of these locals is expanded to the entire switch body, as it is possible to
// share them as temps in the decision dag.
outerVariables.AddRange(arm.Locals);
// Note the language scope of the locals, even though they are included for the purposes of
// lifetime analysis in the enclosing scope.
result.Add(new BoundScope(arm.Syntax, arm.Locals, statements));
}
}
_factory.Syntax = node.Syntax;
if (node.DefaultLabel != null)
{
result.Add(_factory.Label(node.DefaultLabel));
var objectType = _factory.SpecialType(SpecialType.System_Object);
var thrownExpression =
(implicitConversionExists(savedInputExpression, objectType) &&
_factory.WellKnownMember(WellKnownMember.System_Runtime_CompilerServices_SwitchExpressionException__ctorObject, isOptional: true) is MethodSymbol exception1)
? _factory.New(exception1, _factory.Convert(objectType, savedInputExpression)) :
(_factory.WellKnownMember(WellKnownMember.System_Runtime_CompilerServices_SwitchExpressionException__ctor, isOptional: true) is MethodSymbol exception0)
? _factory.New(exception0) :
_factory.New(_factory.WellKnownMethod(WellKnownMember.System_InvalidOperationException__ctor));
result.Add(_factory.Throw(thrownExpression));
}
result.Add(_factory.Label(afterSwitchExpression));
outerVariables.Add(resultTemp);
outerVariables.AddRange(_tempAllocator.AllTemps());
return(_factory.SpillSequence(outerVariables.ToImmutableAndFree(), result.ToImmutableAndFree(), _factory.Local(resultTemp)));
bool implicitConversionExists(BoundExpression expression, TypeSymbol type)
{
HashSet <DiagnosticInfo> discarded = null;
Conversion c = _localRewriter._compilation.Conversions.ClassifyConversionFromExpression(expression, type, ref discarded);
return(c.IsImplicit);
}
}
private SwitchExpressionLocalRewriter(BoundSwitchExpression node, LocalRewriter localRewriter)
: base(node.Syntax, localRewriter, node.SwitchArms.SelectAsArray(arm => arm.Syntax), isSwitchStatement: false)
{
}