private ImmutableArray<BoundPatternSwitchSection> BindPatternSwitchSections(BoundExpression boundSwitchExpression, SyntaxList<SwitchSectionSyntax> sections, Binder originalBinder, out BoundPatternSwitchLabel defaultLabel, DiagnosticBag diagnostics)
{
defaultLabel = null;
// Bind match sections
var boundPatternSwitchSectionsBuilder = ArrayBuilder<BoundPatternSwitchSection>.GetInstance();
foreach (var sectionSyntax in sections)
{
boundPatternSwitchSectionsBuilder.Add(BindPatternSwitchSection(boundSwitchExpression, sectionSyntax, originalBinder, ref defaultLabel, diagnostics));
}
return boundPatternSwitchSectionsBuilder.ToImmutableAndFree();
}
protected DecisionTree AddToDecisionTree(DecisionTree decisionTree, SyntaxNode sectionSyntax, BoundPatternSwitchLabel label)
{
var pattern = label.Pattern;
var guard = label.Guard;
if (guard?.ConstantValue == ConstantValue.False)
{
return null;
}
switch (pattern.Kind)
{
case BoundKind.ConstantPattern:
{
var constantPattern = (BoundConstantPattern)pattern;
DecisionMaker makeDecision = (e, t) => new DecisionTree.Guarded(e, t, default(ImmutableArray<KeyValuePair<BoundExpression, BoundExpression>>), sectionSyntax, guard, label);
if (constantPattern.ConstantValue == ConstantValue.Null)
{
return AddByNull(decisionTree, makeDecision);
}
else
{
return AddByValue(decisionTree, constantPattern, makeDecision);
}
}
case BoundKind.DeclarationPattern:
{
var declarationPattern = (BoundDeclarationPattern)pattern;
DecisionMaker maker =
(e, t) => new DecisionTree.Guarded(e, t, ImmutableArray.Create(new KeyValuePair<BoundExpression, BoundExpression>(e, declarationPattern.VariableAccess)), sectionSyntax, guard, label);
if (declarationPattern.IsVar)
{
return Add(decisionTree, maker);
}
else
{
return AddByType(decisionTree, declarationPattern.DeclaredType.Type, maker);
}
}
case BoundKind.WildcardPattern:
// We do not yet support a wildcard pattern syntax. It is used exclusively
// to model the "default:" case, which is handled specially in the caller.
default:
throw ExceptionUtilities.UnexpectedValue(pattern.Kind);
}
}
private ImmutableArray<BoundPatternSwitchSection> BindPatternSwitchSections(
BoundExpression boundSwitchExpression,
SyntaxList<SwitchSectionSyntax> sections,
Binder originalBinder,
out BoundPatternSwitchLabel defaultLabel,
out bool isComplete,
DiagnosticBag diagnostics)
{
defaultLabel = null;
// true if we found a case label whose value is the same as the input expression's constant value
bool someValueMatched = false;
// Bind match sections
var boundPatternSwitchSectionsBuilder = ArrayBuilder<BoundPatternSwitchSection>.GetInstance();
SubsumptionDiagnosticBuilder subsumption = new SubsumptionDiagnosticBuilder(ContainingMemberOrLambda, this.Conversions, boundSwitchExpression);
foreach (var sectionSyntax in sections)
{
boundPatternSwitchSectionsBuilder.Add(BindPatternSwitchSection(
boundSwitchExpression, sectionSyntax, originalBinder, ref defaultLabel, ref someValueMatched, subsumption, diagnostics));
}
isComplete = defaultLabel != null || subsumption.IsComplete || someValueMatched;
return boundPatternSwitchSectionsBuilder.ToImmutableAndFree();
}
private BoundPatternSwitchLabel BindPatternSwitchSectionLabel(
Binder sectionBinder, BoundExpression boundSwitchExpression, SwitchLabelSyntax node, LabelSymbol label, ref BoundPatternSwitchLabel defaultLabel, DiagnosticBag diagnostics)
{
switch (node.Kind())
{
case SyntaxKind.CaseSwitchLabel:
{
var caseLabelSyntax = (CaseSwitchLabelSyntax)node;
bool wasExpression;
var pattern = sectionBinder.BindConstantPattern(
node, boundSwitchExpression, boundSwitchExpression.Type, caseLabelSyntax.Value, node.HasErrors, diagnostics, out wasExpression, wasSwitchCase: true);
bool hasErrors = pattern.HasErrors;
var constantValue = pattern.ConstantValue;
if (!hasErrors &&
(object)constantValue != null &&
pattern.Value.Type == SwitchGoverningType &&
this.FindMatchingSwitchCaseLabel(constantValue, caseLabelSyntax) != label)
{
diagnostics.Add(ErrorCode.ERR_DuplicateCaseLabel, node.Location, pattern.ConstantValue.GetValueToDisplay() ?? label.Name);
hasErrors = true;
}
// Until we've determined whether or not the switch label is reachable, we assume it
// is. The caller updates isReachable after determining if the label is subsumed.
const bool isReachable = true;
return new BoundPatternSwitchLabel(node, label, pattern, null, isReachable, hasErrors);
}
case SyntaxKind.DefaultSwitchLabel:
{
var defaultLabelSyntax = (DefaultSwitchLabelSyntax)node;
var pattern = new BoundWildcardPattern(node);
bool hasErrors = pattern.HasErrors;
if (defaultLabel != null)
{
diagnostics.Add(ErrorCode.ERR_DuplicateCaseLabel, node.Location, label.Name);
hasErrors = true;
}
// We always treat the default label as reachable, even if the switch is complete.
const bool isReachable = true;
// Note that this is semantically last! The caller will place it in the decision tree
// in the final position.
defaultLabel = new BoundPatternSwitchLabel(node, label, pattern, null, isReachable, hasErrors);
return defaultLabel;
}
case SyntaxKind.CasePatternSwitchLabel:
{
var matchLabelSyntax = (CasePatternSwitchLabelSyntax)node;
var pattern = sectionBinder.BindPattern(
matchLabelSyntax.Pattern, boundSwitchExpression, boundSwitchExpression.Type, node.HasErrors, diagnostics, wasSwitchCase: true);
return new BoundPatternSwitchLabel(node, label, pattern,
matchLabelSyntax.WhenClause != null ? sectionBinder.BindBooleanExpression(matchLabelSyntax.WhenClause.Condition, diagnostics) : null,
true, node.HasErrors);
}
default:
throw ExceptionUtilities.UnexpectedValue(node);
}
}
/// <summary>
/// Bind the pattern switch section, producing subsumption diagnostics.
/// </summary>
/// <param name="boundSwitchExpression"/>
/// <param name="node"/>
/// <param name="originalBinder"/>
/// <param name="defaultLabel">If a default label is found in this section, assigned that label</param>
/// <param name="someValueMatched">If a constant label is found that matches the constant input, assigned that label</param>
/// <param name="subsumption">A helper class that uses a decision tree to produce subsumption diagnostics.</param>
/// <param name="diagnostics"></param>
/// <returns></returns>
private BoundPatternSwitchSection BindPatternSwitchSection(
BoundExpression boundSwitchExpression,
SwitchSectionSyntax node,
Binder originalBinder,
ref BoundPatternSwitchLabel defaultLabel,
ref bool someValueMatched,
SubsumptionDiagnosticBuilder subsumption,
DiagnosticBag diagnostics)
{
// Bind match section labels
var boundLabelsBuilder = ArrayBuilder<BoundPatternSwitchLabel>.GetInstance();
var sectionBinder = originalBinder.GetBinder(node); // this binder can bind pattern variables from the section.
Debug.Assert(sectionBinder != null);
var labelsByNode = LabelsByNode;
foreach (var labelSyntax in node.Labels)
{
LabelSymbol label = labelsByNode[labelSyntax];
BoundPatternSwitchLabel boundLabel = BindPatternSwitchSectionLabel(sectionBinder, boundSwitchExpression, labelSyntax, label, ref defaultLabel, diagnostics);
bool valueMatched; // true if we find an unconditional constant label that matches the input constant's value
bool isReachable = subsumption.AddLabel(boundLabel, diagnostics, out valueMatched);
boundLabel = boundLabel.Update(boundLabel.Label, boundLabel.Pattern, boundLabel.Guard, isReachable && !someValueMatched);
someValueMatched |= valueMatched;
boundLabelsBuilder.Add(boundLabel);
}
// Bind switch section statements
var boundStatementsBuilder = ArrayBuilder<BoundStatement>.GetInstance();
foreach (var statement in node.Statements)
{
boundStatementsBuilder.Add(sectionBinder.BindStatement(statement, diagnostics));
}
return new BoundPatternSwitchSection(node, sectionBinder.GetDeclaredLocalsForScope(node), boundLabelsBuilder.ToImmutableAndFree(), boundStatementsBuilder.ToImmutableAndFree());
}
private BoundPatternSwitchSection BindPatternSwitchSection(
BoundExpression boundSwitchExpression,
SwitchSectionSyntax node,
Binder originalBinder,
ref BoundPatternSwitchLabel defaultLabel,
DiagnosticBag diagnostics)
{
// Bind match section labels
var boundLabelsBuilder = ArrayBuilder<BoundPatternSwitchLabel>.GetInstance();
var sectionBinder = originalBinder.GetBinder(node); // this binder can bind pattern variables from the section.
Debug.Assert(sectionBinder != null);
var labelsByNode = LabelsByNode;
foreach (var labelSyntax in node.Labels)
{
LabelSymbol label = labelsByNode[labelSyntax];
BoundPatternSwitchLabel boundLabel = BindPatternSwitchSectionLabel(sectionBinder, boundSwitchExpression, labelSyntax, label, ref defaultLabel, diagnostics);
boundLabelsBuilder.Add(boundLabel);
}
// Bind switch section statements
var boundStatementsBuilder = ArrayBuilder<BoundStatement>.GetInstance();
foreach (var statement in node.Statements)
{
boundStatementsBuilder.Add(sectionBinder.BindStatement(statement, diagnostics));
}
return new BoundPatternSwitchSection(node, sectionBinder.GetDeclaredLocalsForScope(node), boundLabelsBuilder.ToImmutableAndFree(), boundStatementsBuilder.ToImmutableAndFree());
}
private BoundPatternSwitchLabel BindPatternSwitchSectionLabel(
Binder sectionBinder, BoundExpression boundSwitchExpression, SwitchLabelSyntax node, LabelSymbol label, ref BoundPatternSwitchLabel defaultLabel, DiagnosticBag diagnostics)
{
switch (node.Kind())
{
case SyntaxKind.CaseSwitchLabel:
{
var caseLabelSyntax = (CaseSwitchLabelSyntax)node;
bool wasExpression;
var pattern = sectionBinder.BindConstantPattern(
node, boundSwitchExpression, boundSwitchExpression.Type, caseLabelSyntax.Value, node.HasErrors, diagnostics, out wasExpression, wasSwitchCase: true);
bool hasErrors = pattern.HasErrors;
var constantValue = pattern.ConstantValue;
if (!hasErrors && (object)constantValue != null && this.FindMatchingSwitchCaseLabel(constantValue, caseLabelSyntax) != label)
{
diagnostics.Add(ErrorCode.ERR_DuplicateCaseLabel, node.Location, pattern.ConstantValue.GetValueToDisplay() ?? label.Name);
hasErrors = true;
}
return new BoundPatternSwitchLabel(node, label, pattern, null, hasErrors);
}
case SyntaxKind.DefaultSwitchLabel:
{
var defaultLabelSyntax = (DefaultSwitchLabelSyntax)node;
var pattern = new BoundWildcardPattern(node);
bool hasErrors = pattern.HasErrors;
if (defaultLabel != null)
{
diagnostics.Add(ErrorCode.ERR_DuplicateCaseLabel, node.Location, "default");
hasErrors = true;
}
// Note that this is semantically last! The caller will place it in the decision tree
// in the final position.
defaultLabel = new BoundPatternSwitchLabel(node, label, pattern, null, hasErrors);
return defaultLabel;
}
case SyntaxKind.CasePatternSwitchLabel:
{
var matchLabelSyntax = (CasePatternSwitchLabelSyntax)node;
var pattern = sectionBinder.BindPattern(
matchLabelSyntax.Pattern, boundSwitchExpression, boundSwitchExpression.Type, node.HasErrors, diagnostics, wasSwitchCase: true);
return new BoundPatternSwitchLabel(node, label, pattern,
matchLabelSyntax.WhenClause != null ? sectionBinder.BindBooleanExpression(matchLabelSyntax.WhenClause.Condition, diagnostics) : null, node.HasErrors);
}
default:
throw ExceptionUtilities.UnexpectedValue(node);
}
}
private BoundPatternSwitchLabel LowerSwitchLabel(BoundPatternSwitchLabel label)
{
return label.Update(label.Label, _localRewriter.LowerPattern(label.Pattern), _localRewriter.VisitExpression(label.Guard), label.IsReachable);
}
/// <summary>
/// Add the case label to the subsumption tree. Return true if the label is reachable
/// given the expression and previously added labels. `valueMatched` is set to true
/// if and only if the label is a reachable unconditional (no when clause) constant pattern
/// whose value is the same as the input expression's constant value, and false otherwise.
/// </summary>
internal bool AddLabel(BoundPatternSwitchLabel label, DiagnosticBag diagnostics, out bool valueMatched)
{
// Use site diagnostics are reported (and cleared) by this method.
// So they should be empty when we start.
Debug.Assert(_useSiteDiagnostics.Count == 0);
valueMatched = false;
if (label.Syntax.Kind() == SyntaxKind.DefaultSwitchLabel)
{
// the default case label is always considered reachable.
return true;
}
try
{
// For purposes of subsumption, we do not take into consideration the value
// of the input expression. Therefore we consider null possible if the type permits.
Syntax = label.Syntax;
var subsumedErrorCode = CheckSubsumed(label.Pattern, _subsumptionTree, inputCouldBeNull: true);
if (subsumedErrorCode != 0 && subsumedErrorCode != ErrorCode.ERR_NoImplicitConvCast)
{
if (!label.HasErrors)
{
diagnostics.Add(subsumedErrorCode, label.Pattern.Syntax.Location);
}
return false;
}
var guardAlwaysSatisfied = label.Guard == null || label.Guard.ConstantValue == ConstantValue.True;
if (guardAlwaysSatisfied)
{
// Only unconditional switch labels contribute to subsumption
if (AddToDecisionTree(_subsumptionTree, null, label) == null)
{
return false;
}
}
// For a constant switch, a constant label is only reachable if the value is equal.
var patternConstant = (label.Pattern as BoundConstantPattern)?.ConstantValue;
if (this._subsumptionTree.Expression.ConstantValue == null ||
patternConstant == null)
{
// either the input or the pattern wasn't a constant, so they might match.
return true;
}
// If not subsumed, the label is considered reachable unless its constant value is
// distinct from the constant value of the input expression.
if (this._subsumptionTree.Expression.ConstantValue.Equals(patternConstant))
{
valueMatched = guardAlwaysSatisfied;
return true;
}
return false;
}
finally
{
// report the use-site diagnostics
diagnostics.Add(label.Syntax.Location, _useSiteDiagnostics);
_useSiteDiagnostics.Clear();
}
}
private void AddToDecisionTree(DecisionTree decisionTree, BoundPatternSwitchLabel label)
{
var pattern = label.Pattern;
var guard = label.Guard;
if (guard?.ConstantValue == ConstantValue.False)
{
return;
}
switch (pattern.Kind)
{
case BoundKind.ConstantPattern:
{
var constantPattern = (BoundConstantPattern)pattern;
AddByValue(decisionTree, constantPattern.Value, (e, t) => new DecisionTree.Guarded(e, t, default(ImmutableArray<KeyValuePair<BoundExpression, LocalSymbol>>), _section, guard, label), label.HasErrors);
break;
}
case BoundKind.DeclarationPattern:
{
var declarationPattern = (BoundDeclarationPattern)pattern;
DecisionMaker maker = (e, t) => new DecisionTree.Guarded(e, t, ImmutableArray.Create(new KeyValuePair<BoundExpression, LocalSymbol>(e, declarationPattern.LocalSymbol)), _section, guard, label);
if (declarationPattern.IsVar)
{
Add(decisionTree, maker);
}
else
{
AddByType(decisionTree, declarationPattern.DeclaredType.Type, maker);
}
break;
}
case BoundKind.WildcardPattern:
// We do not yet support a wildcard pattern syntax. It is used exclusively
// to model the "default:" case, which is handled specially in the caller.
default:
throw ExceptionUtilities.UnexpectedValue(pattern.Kind);
}
}
public Guarded(
BoundExpression expression,
TypeSymbol type,
ImmutableArray<KeyValuePair<BoundExpression, LocalSymbol>> bindings,
BoundPatternSwitchSection section,
BoundExpression guard,
BoundPatternSwitchLabel label)
: base(expression, type, null)
{
this.Guard = guard;
this.Label = label;
this.Bindings = bindings;
this.Section = section;
Debug.Assert(guard?.ConstantValue != ConstantValue.False);
base.MatchIsComplete =
(guard == null) || (guard.ConstantValue == ConstantValue.True);
}
