// If binder is null, then get it from the compilation. Otherwise use the provided binder.
// Don't always get it from the compilation because we might be in a speculative context (local function parameter),
// in which case the declaring compilation is the wrong one.
protected ConstantValue MakeDefaultExpression(DiagnosticBag diagnostics, Binder binder)
{
var parameterSyntax = this.CSharpSyntaxNode;
if (parameterSyntax == null)
{
return(ConstantValue.NotAvailable);
}
var defaultSyntax = parameterSyntax.Default;
if (defaultSyntax == null)
{
return(ConstantValue.NotAvailable);
}
if (binder == null)
{
var syntaxTree = _syntaxRef.SyntaxTree;
var compilation = this.DeclaringCompilation;
var binderFactory = compilation.GetBinderFactory(syntaxTree);
binder = binderFactory.GetBinder(defaultSyntax);
}
Debug.Assert(binder.GetBinder(defaultSyntax) == null);
Binder binderForDefault = binder.CreateBinderForParameterDefaultValue(this, defaultSyntax);
Debug.Assert(binderForDefault.InParameterDefaultValue);
Debug.Assert(binderForDefault.ContainingMemberOrLambda == ContainingSymbol);
BoundExpression valueBeforeConversion;
var convertedExpression = binderForDefault.BindParameterDefaultValue(defaultSyntax, parameterType, diagnostics, out valueBeforeConversion);
bool hasErrors = ParameterHelpers.ReportDefaultParameterErrors(binder, ContainingSymbol, parameterSyntax, this, valueBeforeConversion, diagnostics);
if (hasErrors)
{
return(ConstantValue.Bad);
}
// If we have something like M(double? x = 1) then the expression we'll get is (double?)1, which
// does not have a constant value. The constant value we want is (double)1.
if (convertedExpression.ConstantValue == null && convertedExpression.Kind == BoundKind.Conversion)
{
if (parameterType.IsNullableType())
{
convertedExpression = binder.GenerateConversionForAssignment(parameterType.GetNullableUnderlyingType(),
valueBeforeConversion, diagnostics, isDefaultParameter: true);
}
}
// represent default(struct) by a Null constant:
var value = convertedExpression.ConstantValue ?? ConstantValue.Null;
VerifyParamDefaultValueMatchesAttributeIfAny(value, defaultSyntax.Value, diagnostics);
return(value);
}
