private NamedTypeSymbol DecodeNamedType(NamedTypeSymbol type)
{
// First decode the type arguments
var typeArgs = type.TypeArgumentsWithAnnotationsNoUseSiteDiagnostics;
var decodedArgs = DecodeTypeArguments(typeArgs);
NamedTypeSymbol decodedType = type;
// Now check the container
NamedTypeSymbol containingType = type.ContainingType;
NamedTypeSymbol?decodedContainingType;
if (containingType is object && containingType.IsGenericType)
{
decodedContainingType = DecodeNamedType(containingType);
Debug.Assert(decodedContainingType.IsGenericType);
}
else
{
decodedContainingType = containingType;
}
// Replace the type if necessary
var containerChanged = !ReferenceEquals(decodedContainingType, containingType);
var typeArgsChanged = typeArgs != decodedArgs;
if (typeArgsChanged || containerChanged)
{
if (containerChanged)
{
decodedType = decodedType.OriginalDefinition.AsMember(decodedContainingType);
// If the type is nested, e.g. Outer<T>.Inner<V>, then Inner is definitely
// not a tuple, since we know all tuple-compatible types (System.ValueTuple)
// are not nested types. Thus, it is safe to return without checking if
// Inner is a tuple.
return(decodedType.ConstructIfGeneric(decodedArgs));
}
decodedType = type.ConstructedFrom.Construct(decodedArgs, unbound: false);
}
// Now decode into a tuple, if it is one
if (decodedType.IsTupleType)
{
int tupleCardinality = decodedType.TupleElementTypesWithAnnotations.Length;
if (tupleCardinality > 0)
{
var elementNames = EatElementNamesIfAvailable(tupleCardinality);
Debug.Assert(elementNames.IsDefault || elementNames.Length == tupleCardinality);
decodedType = NamedTypeSymbol.CreateTuple(decodedType, elementNames);
}
}
return(decodedType);
}
private BoundTupleExpression DeconstructionVariablesAsTuple(CSharpSyntaxNode syntax, ArrayBuilder <DeconstructionVariable> variables,
DiagnosticBag diagnostics, bool ignoreDiagnosticsFromTuple)
{
int count = variables.Count;
var valuesBuilder = ArrayBuilder <BoundExpression> .GetInstance(count);
var typesWithAnnotationsBuilder = ArrayBuilder <TypeWithAnnotations> .GetInstance(count);
var locationsBuilder = ArrayBuilder <Location> .GetInstance(count);
var namesBuilder = ArrayBuilder <string> .GetInstance(count);
foreach (var variable in variables)
{
BoundExpression value;
if (variable.HasNestedVariables)
{
value = DeconstructionVariablesAsTuple(variable.Syntax, variable.NestedVariables, diagnostics, ignoreDiagnosticsFromTuple);
namesBuilder.Add(null);
}
else
{
value = variable.Single;
namesBuilder.Add(ExtractDeconstructResultElementName(value));
}
valuesBuilder.Add(value);
typesWithAnnotationsBuilder.Add(TypeWithAnnotations.Create(value.Type));
locationsBuilder.Add(variable.Syntax.Location);
}
ImmutableArray <BoundExpression> arguments = valuesBuilder.ToImmutableAndFree();
var uniqueFieldNames = PooledHashSet <string> .GetInstance();
RemoveDuplicateInferredTupleNamesAndFreeIfEmptied(ref namesBuilder, uniqueFieldNames);
uniqueFieldNames.Free();
ImmutableArray <string> tupleNames = namesBuilder is null ? default : namesBuilder.ToImmutableAndFree();
ImmutableArray <bool> inferredPositions = tupleNames.IsDefault ? default : tupleNames.SelectAsArray(n => n != null);
bool disallowInferredNames = this.Compilation.LanguageVersion.DisallowInferredTupleElementNames();
var type = NamedTypeSymbol.CreateTuple(
syntax.Location,
typesWithAnnotationsBuilder.ToImmutableAndFree(), locationsBuilder.ToImmutableAndFree(),
tupleNames, this.Compilation,
shouldCheckConstraints: !ignoreDiagnosticsFromTuple,
includeNullability: false,
errorPositions: disallowInferredNames ? inferredPositions : default,
/// <summary>
/// For cases where the RHS of a deconstruction-declaration is a tuple literal, we merge type information from both the LHS and RHS.
/// For cases where the RHS of a deconstruction-assignment is a tuple literal, the type information from the LHS determines the merged type, since all variables have a type.
/// Returns null if a merged tuple type could not be fabricated.
/// </summary>
private static TypeSymbol MakeMergedTupleType(ArrayBuilder <DeconstructionVariable> lhsVariables, BoundTupleLiteral rhsLiteral, CSharpSyntaxNode syntax, CSharpCompilation compilation, DiagnosticBag diagnostics)
{
int leftLength = lhsVariables.Count;
int rightLength = rhsLiteral.Arguments.Length;
var typesWithAnnotationsBuilder = ArrayBuilder <TypeWithAnnotations> .GetInstance(leftLength);
var locationsBuilder = ArrayBuilder <Location> .GetInstance(leftLength);
for (int i = 0; i < rightLength; i++)
{
BoundExpression element = rhsLiteral.Arguments[i];
TypeSymbol mergedType = element.Type;
if (i < leftLength)
{
var variable = lhsVariables[i];
if (variable.HasNestedVariables)
{
if (element.Kind == BoundKind.TupleLiteral)
{
// (variables) on the left and (elements) on the right
mergedType = MakeMergedTupleType(variable.NestedVariables, (BoundTupleLiteral)element, syntax, compilation, diagnostics);
}
else if ((object)mergedType == null)
{
// (variables) on the left and null on the right
Error(diagnostics, ErrorCode.ERR_DeconstructRequiresExpression, element.Syntax);
}
}
else
{
if ((object)variable.Single.Type != null)
{
// typed-variable on the left
mergedType = variable.Single.Type;
}
}
}
else
{
if ((object)mergedType == null)
{
// a typeless element on the right, matching no variable on the left
Error(diagnostics, ErrorCode.ERR_DeconstructRequiresExpression, element.Syntax);
}
}
typesWithAnnotationsBuilder.Add(TypeWithAnnotations.Create(mergedType));
locationsBuilder.Add(element.Syntax.Location);
}
if (typesWithAnnotationsBuilder.Any(t => !t.HasType))
{
typesWithAnnotationsBuilder.Free();
locationsBuilder.Free();
return(null);
}
// The tuple created here is not identical to the one created by
// DeconstructionVariablesAsTuple. It represents a smaller
// tree of types used for figuring out natural types in tuple literal.
return(NamedTypeSymbol.CreateTuple(
locationOpt: null,
elementTypesWithAnnotations: typesWithAnnotationsBuilder.ToImmutableAndFree(),
elementLocations: locationsBuilder.ToImmutableAndFree(),
elementNames: default(ImmutableArray <string>),
compilation: compilation,
diagnostics: diagnostics,
shouldCheckConstraints: true,
includeNullability: false,
errorPositions: default(ImmutableArray <bool>),
syntax: syntax));
}
