internal static TypeSymbol CopyTypeCustomModifiers(TypeSymbol sourceType, TypeSymbol destinationType, AssemblySymbol containingAssembly)
{
Debug.Assert(sourceType.Equals(destinationType, TypeCompareKind.AllIgnoreOptions));
const RefKind refKind = RefKind.None;
// NOTE: overrides can differ by object/dynamic, tuple element names, etc.
// If they do, we'll need to tweak destinationType before we can use it in place of sourceType.
// NOTE: refKind is irrelevant here since we are just encoding/decoding the type.
ImmutableArray <bool> flags = CSharpCompilation.DynamicTransformsEncoder.EncodeWithoutCustomModifierFlags(destinationType, refKind);
TypeSymbol resultType = DynamicTypeDecoder.TransformTypeWithoutCustomModifierFlags(sourceType, containingAssembly, refKind, flags);
if (!containingAssembly.RuntimeSupportsNumericIntPtr)
{
var builder = ArrayBuilder <bool> .GetInstance();
CSharpCompilation.NativeIntegerTransformsEncoder.Encode(builder, destinationType);
resultType = NativeIntegerTypeDecoder.TransformType(resultType, builder.ToImmutableAndFree());
}
if (destinationType.ContainsTuple() && !sourceType.Equals(destinationType, TypeCompareKind.IgnoreCustomModifiersAndArraySizesAndLowerBounds | TypeCompareKind.IgnoreNullableModifiersForReferenceTypes | TypeCompareKind.IgnoreDynamic))
{
// We also preserve tuple names, if present and different
ImmutableArray <string> names = CSharpCompilation.TupleNamesEncoder.Encode(destinationType);
resultType = TupleTypeDecoder.DecodeTupleTypesIfApplicable(resultType, names);
}
// Preserve nullable modifiers as well.
// https://github.com/dotnet/roslyn/issues/30077: Is it reasonable to copy annotations from the source?
// If the destination had some of those annotations but not all, then clearly the destination
// was incorrect. Or if the destination is C#7, then the destination will advertise annotations
// that the author did not write and did not validate.
var flagsBuilder = ArrayBuilder <byte> .GetInstance();
destinationType.AddNullableTransforms(flagsBuilder);
int position = 0;
int length = flagsBuilder.Count;
bool transformResult = resultType.ApplyNullableTransforms(defaultTransformFlag: 0, flagsBuilder.ToImmutableAndFree(), ref position, out resultType);
Debug.Assert(transformResult && position == length);
Debug.Assert(resultType.Equals(sourceType, TypeCompareKind.IgnoreDynamicAndTupleNames | TypeCompareKind.IgnoreNullableModifiersForReferenceTypes | TypeCompareKind.IgnoreNativeIntegers)); // Same custom modifiers as source type.
// Same object/dynamic, nullability, native integers, and tuple names as destination type.
Debug.Assert(resultType.Equals(destinationType, TypeCompareKind.IgnoreCustomModifiersAndArraySizesAndLowerBounds));
return(resultType);
}