/// <summary>
/// Record declared variables in the pattern.
/// </summary>
private void NoteDeclaredPatternVariables(BoundPattern pattern)
{
if (IsInside)
{
switch (pattern)
{
case BoundDeclarationPattern decl:
{
// The variable may be null if it is a discard designation `_`.
if (decl.Variable?.Kind == SymbolKind.Local)
{
// Because this API only returns local symbols and parameters,
// we exclude pattern variables that have become fields in scripts.
_variablesDeclared.Add(decl.Variable);
}
}
break;
case BoundRecursivePattern recur:
{
if (recur.Variable?.Kind == SymbolKind.Local)
{
_variablesDeclared.Add(recur.Variable);
}
}
break;
}
}
}
internal override BoundSwitchExpressionArm BindSwitchExpressionArm(SwitchExpressionArmSyntax node, DiagnosticBag diagnostics)
{
Debug.Assert(node == _arm);
Binder armBinder = this.GetBinder(node);
bool hasErrors = _switchExpressionBinder.SwitchGoverningType.IsErrorType();
ImmutableArray <LocalSymbol> locals = _armScopeBinder.Locals;
BoundPattern pattern = armBinder.BindPattern(node.Pattern, _switchExpressionBinder.SwitchGoverningType, _switchExpressionBinder.SwitchGoverningValEscape, hasErrors, diagnostics);
BoundExpression whenClause = node.WhenClause != null
? armBinder.BindBooleanExpression(node.WhenClause.Condition, diagnostics)
: null;
BoundExpression armResult = armBinder.BindValue(node.Expression, diagnostics, BindValueKind.RValue);
var label = new GeneratedLabelSymbol("arm");
return(new BoundSwitchExpressionArm(node, locals, pattern, whenClause, armResult, label, hasErrors | pattern.HasErrors));
}
public BoundExpression LowerIsPattern(
BoundIsPatternExpression isPatternExpression, BoundPattern pattern, CSharpCompilation compilation, DiagnosticBag diagnostics)
{
BoundDecisionDag decisionDag = isPatternExpression.DecisionDag;
LabelSymbol whenTrueLabel = isPatternExpression.WhenTrueLabel;
LabelSymbol whenFalseLabel = isPatternExpression.WhenFalseLabel;
BoundExpression loweredInput = _localRewriter.VisitExpression(isPatternExpression.Expression);
// The optimization of sharing pattern-matching temps with user variables can always apply to
// an is-pattern expression because there is no when clause that could possibly intervene during
// the execution of the pattern-matching automaton and change one of those variables.
decisionDag = ShareTempsAndEvaluateInput(loweredInput, decisionDag, expr => _sideEffectBuilder.Add(expr), out _);
var node = decisionDag.RootNode;
// We follow the "good" path in the decision dag. We depend on it being nicely linear in structure.
// If we add "or" patterns that assumption breaks down.
while (node.Kind != BoundKind.LeafDecisionDagNode && node.Kind != BoundKind.WhenDecisionDagNode)
{
switch (node)
{
case BoundEvaluationDecisionDagNode evalNode:
{
LowerOneTest(evalNode.Evaluation);
node = evalNode.Next;
}
break;
case BoundTestDecisionDagNode testNode:
{
Debug.Assert(testNode.WhenFalse is BoundLeafDecisionDagNode x && x.Label == whenFalseLabel);
if (testNode.WhenTrue is BoundEvaluationDecisionDagNode e &&
TryLowerTypeTestAndCast(testNode.Test, e.Evaluation, out BoundExpression sideEffect, out BoundExpression testExpression))
{
_sideEffectBuilder.Add(sideEffect);
AddConjunct(testExpression);
node = e.Next;
}
public override void VisitPattern(BoundPattern pattern)
{
base.VisitPattern(pattern);
NoteDeclaredPatternVariables(pattern);
}