/// <summary>
/// Lower a test followed by an evaluation into a side-effect followed by a test. This permits us to optimize
/// a type test followed by a cast into an `as` expression followed by a null check. Returns true if the optimization
/// applies and the results are placed into <paramref name="sideEffect"/> and <paramref name="test"/>. The caller
/// should place the side-effect before the test in the generated code.
/// </summary>
/// <param name="evaluation"></param>
/// <param name="test"></param>
/// <param name="sideEffect"></param>
/// <param name="testExpression"></param>
/// <returns>true if the optimization is applied</returns>
protected bool TryLowerTypeTestAndCast(
BoundDagTest test,
BoundDagEvaluation evaluation,
out BoundExpression sideEffect,
out BoundExpression testExpression)
{
if (test is BoundDagTypeTest typeDecision &&
evaluation is BoundDagTypeEvaluation typeEvaluation &&
typeDecision.Type.IsReferenceType &&
typeEvaluation.Type.Equals(typeDecision.Type, TypeCompareKind.AllIgnoreOptions) &&
typeEvaluation.Input == typeDecision.Input
)
{
BoundExpression input = _tempAllocator.GetTemp(test.Input);
BoundExpression output = _tempAllocator.GetTemp(new BoundDagTemp(evaluation.Syntax, typeEvaluation.Type, evaluation, index: 0));
sideEffect = _factory.AssignmentExpression(output, _factory.As(input, typeEvaluation.Type));
testExpression = _factory.ObjectNotEqual(output, _factory.Null(output.Type));
return(true);
}
sideEffect = testExpression = null;
return(false);
}
public override bool Equals(BoundDagEvaluation obj)
{
return(base.Equals(obj) &&
// base.Equals checks the kind field, so the following cast is safe
this.Index == ((BoundDagIndexEvaluation)obj).Index);
}
/// <summary>
/// Return the side-effect expression corresponding to an evaluation.
/// </summary>
protected BoundExpression LowerEvaluation(BoundDagEvaluation evaluation)
{
BoundExpression input = _tempAllocator.GetTemp(evaluation.Input);
switch (evaluation)
{
case BoundDagFieldEvaluation f:
{
FieldSymbol field = f.Field;
var outputTemp = new BoundDagTemp(f.Syntax, field.Type.TypeSymbol, f, index: 0);
BoundExpression output = _tempAllocator.GetTemp(outputTemp);
BoundExpression access = _localRewriter.MakeFieldAccess(f.Syntax, input, field, null, LookupResultKind.Viable, field.Type.TypeSymbol);
access.WasCompilerGenerated = true;
return(_factory.AssignmentExpression(output, access));
}
case BoundDagPropertyEvaluation p:
{
PropertySymbol property = p.Property;
var outputTemp = new BoundDagTemp(p.Syntax, property.Type.TypeSymbol, p, index: 0);
BoundExpression output = _tempAllocator.GetTemp(outputTemp);
return(_factory.AssignmentExpression(output, _factory.Property(input, property)));
}
case BoundDagDeconstructEvaluation d:
{
MethodSymbol method = d.DeconstructMethod;
var refKindBuilder = ArrayBuilder <RefKind> .GetInstance();
var argBuilder = ArrayBuilder <BoundExpression> .GetInstance();
BoundExpression receiver;
void addArg(RefKind refKind, BoundExpression expression)
{
refKindBuilder.Add(refKind);
argBuilder.Add(expression);
}
Debug.Assert(method.Name == WellKnownMemberNames.DeconstructMethodName);
int extensionExtra;
if (method.IsStatic)
{
Debug.Assert(method.IsExtensionMethod);
receiver = _factory.Type(method.ContainingType);
addArg(method.ParameterRefKinds[0], input);
extensionExtra = 1;
}
else
{
receiver = input;
extensionExtra = 0;
}
for (int i = extensionExtra; i < method.ParameterCount; i++)
{
ParameterSymbol parameter = method.Parameters[i];
Debug.Assert(parameter.RefKind == RefKind.Out);
var outputTemp = new BoundDagTemp(d.Syntax, parameter.Type.TypeSymbol, d, i - extensionExtra);
addArg(RefKind.Out, _tempAllocator.GetTemp(outputTemp));
}
return(_factory.Call(receiver, method, refKindBuilder.ToImmutableAndFree(), argBuilder.ToImmutableAndFree()));
}
case BoundDagTypeEvaluation t:
{
TypeSymbol inputType = input.Type;
if (inputType.IsDynamic() || inputType.ContainsTypeParameter())
{
inputType = _factory.SpecialType(SpecialType.System_Object);
}
TypeSymbol type = t.Type;
var outputTemp = new BoundDagTemp(t.Syntax, type, t, index: 0);
BoundExpression output = _tempAllocator.GetTemp(outputTemp);
HashSet <DiagnosticInfo> useSiteDiagnostics = null;
Conversion conversion = _factory.Compilation.Conversions.ClassifyBuiltInConversion(inputType, output.Type, ref useSiteDiagnostics);
_localRewriter._diagnostics.Add(t.Syntax, useSiteDiagnostics);
BoundExpression evaluated;
if (conversion.Exists)
{
if (conversion.Kind == ConversionKind.ExplicitNullable &&
inputType.GetNullableUnderlyingType().Equals(output.Type, TypeCompareKind.AllIgnoreOptions) &&
_localRewriter.TryGetNullableMethod(t.Syntax, inputType, SpecialMember.System_Nullable_T_GetValueOrDefault, out MethodSymbol getValueOrDefault))
{
// As a special case, since the null test has already been done we can use Nullable<T>.GetValueOrDefault
evaluated = _factory.Call(input, getValueOrDefault);
}
else
{
evaluated = _factory.Convert(type, input, conversion);
}
}
else
{
evaluated = _factory.As(input, type);
}
return(_factory.AssignmentExpression(output, evaluated));
}
case BoundDagIndexEvaluation e:
{
// This is an evaluation of an indexed property with a constant int value.
// The input type must be ITuple, and the property must be a property of ITuple.
Debug.Assert(e.Property.ContainingSymbol.Equals(input.Type));
Debug.Assert(e.Property.GetMethod.ParameterCount == 1);
Debug.Assert(e.Property.GetMethod.Parameters[0].Type.SpecialType == SpecialType.System_Int32);
TypeSymbol type = e.Property.GetMethod.ReturnType.TypeSymbol;
var outputTemp = new BoundDagTemp(e.Syntax, type, e, index: 0);
BoundExpression output = _tempAllocator.GetTemp(outputTemp);
return(_factory.AssignmentExpression(output, _factory.Call(input, e.Property.GetMethod, _factory.Literal(e.Index))));
}
default:
throw ExceptionUtilities.UnexpectedValue(evaluation);
}
}
public virtual bool Equals(BoundDagEvaluation other)
{
return(other != (object)null && this.Kind == other.Kind && this.Input.Equals(other.Input) && this.Symbol == other.Symbol);
}
