private MutabilityInspectionResult InspectConcreteType(
ITypeSymbol type,
HashSet <ITypeSymbol> typeStack,
MutabilityInspectionFlags flags = MutabilityInspectionFlags.Default
)
{
if (type is IErrorTypeSymbol)
{
return(MutabilityInspectionResult.NotMutable());
}
// The concrete type System.Object is empty (and therefore safe.)
// For example, `private readonly object m_lock = new object();` is fine.
if (type.SpecialType == SpecialType.System_Object)
{
return(MutabilityInspectionResult.NotMutable());
}
// System.ValueType is the base class of all value types (obscure detail)
if (type.SpecialType == SpecialType.System_ValueType)
{
return(MutabilityInspectionResult.NotMutable());
}
var scope = type.GetImmutabilityScope();
if (!flags.HasFlag(MutabilityInspectionFlags.IgnoreImmutabilityAttribute) && scope != ImmutabilityScope.None)
{
ImmutableHashSet <string> immutableExceptions = type.GetAllImmutableExceptions();
return(MutabilityInspectionResult.NotMutable(immutableExceptions));
}
return(InspectType(
type,
flags | MutabilityInspectionFlags.AllowUnsealed,
typeStack
));
}
private MutabilityInspectionResult InspectTypeImpl(
ITypeSymbol type,
MutabilityInspectionFlags flags,
HashSet <ITypeSymbol> typeStack
)
{
if (type is IErrorTypeSymbol)
{
// This only happens for code that otherwise won't compile. Our
// analyzer doesn't need to validate these types. It only needs
// to be strict for valid code.
return(MutabilityInspectionResult.NotMutable());
}
if (type == null)
{
throw new Exception("Type cannot be resolved. Please ensure all dependencies "
+ "are referenced, including transitive dependencies.");
}
// If we're not verifying immutability, we might be able to bail out early
var scope = type.GetImmutabilityScope();
if (!flags.HasFlag(MutabilityInspectionFlags.IgnoreImmutabilityAttribute) && scope == ImmutabilityScope.SelfAndChildren)
{
ImmutableHashSet <string> immutableExceptions = type.GetAllImmutableExceptions();
return(MutabilityInspectionResult.NotMutable(immutableExceptions));
}
if (m_knownImmutableTypes.IsTypeKnownImmutable(type))
{
return(MutabilityInspectionResult.NotMutable());
}
if (IsAnImmutableContainerType(type))
{
return(InspectImmutableContainerType(type, typeStack));
}
if (!flags.HasFlag(MutabilityInspectionFlags.AllowUnsealed) &&
type.TypeKind == TypeKind.Class &&
!type.IsSealed
)
{
return(MutabilityInspectionResult.MutableType(type, MutabilityCause.IsNotSealed));
}
switch (type.TypeKind)
{
case TypeKind.Array:
// Arrays are always mutable because you can rebind the
// individual elements.
return(MutabilityInspectionResult.MutableType(
type,
MutabilityCause.IsAnArray
));
case TypeKind.Delegate:
// Delegates can hold state so are mutable in general.
return(MutabilityInspectionResult.MutableType(
type,
MutabilityCause.IsADelegate
));
case TypeKind.Dynamic:
// Dynamic types are always mutable
return(MutabilityInspectionResult.MutableType(
type,
MutabilityCause.IsDynamic
));
case TypeKind.Enum:
// Enums are just fancy ints.
return(MutabilityInspectionResult.NotMutable());
case TypeKind.TypeParameter:
return(InspectTypeParameter(
type,
typeStack
));
case TypeKind.Interface:
return(MutabilityInspectionResult.MutableType(type, MutabilityCause.IsAnInterface));
case TypeKind.Class:
case TypeKind.Struct: // equivalent to TypeKind.Structure
return(InspectClassOrStruct(
type,
typeStack
));
case TypeKind.Error:
// This only happens when the build is failing for other
// (more fundamental) reasons. We only need to be strict
// for otherwise-successful builds, so we bail analysis in
// this case.
return(MutabilityInspectionResult.NotMutable());
case TypeKind.Unknown:
// Looking at the Roslyn source this doesn't appear to
// happen outside their tests. It is value 0 in the enum so
// it may just be a safety guard.
throw new NotImplementedException();
default:
// not handled: Module, Pointer, Submission.
throw new NotImplementedException(
$"TypeKind.{type.Kind} not handled by analysis"
);
}
}
private bool IsTypeMutableRecursive(
ITypeSymbol type,
MutabilityInspectionFlags flags,
HashSet <ITypeSymbol> typeStack
)
{
if (type is IErrorTypeSymbol || type == null)
{
throw new Exception($"Type '{type}' cannot be resolved. Please ensure all dependencies "
+ "are referenced, including transitive dependencies.");
}
if (IsTypeKnownImmutable(type))
{
return(false);
}
if (type.TypeKind == TypeKind.Array)
{
return(true);
}
if (!flags.HasFlag(MutabilityInspectionFlags.IgnoreImmutabilityAttribute) && IsTypeMarkedImmutable(type))
{
return(false);
}
if (typeStack.Contains(type))
{
// We have a cycle. If we're here, it means that either some read-only member causes the cycle (via IsMemberMutableRecursive),
// or a generic parameter to a type causes the cycle (via IsTypeMutableRecursive). This is safe if the checks above have
// passed and the remaining members are read-only immutable. So we can skip the current check, and allow the type to continue
// to be evaluated.
return(false);
}
typeStack.Add(type);
try {
if (ImmutableContainerTypes.Contains(type.GetFullTypeName()))
{
var namedType = type as INamedTypeSymbol;
bool isMutable = namedType.TypeArguments.Any(t => IsTypeMutableRecursive(t, MutabilityInspectionFlags.Default, typeStack));
return(isMutable);
}
if (type.TypeKind == TypeKind.Interface)
{
return(true);
}
if (!flags.HasFlag(MutabilityInspectionFlags.AllowUnsealed) &&
type.TypeKind == TypeKind.Class &&
!type.IsSealed
)
{
return(true);
}
foreach (ISymbol member in type.GetNonStaticMembers())
{
if (IsMemberMutableRecursive(member, MutabilityInspectionFlags.Default, typeStack))
{
return(true);
}
}
return(false);
} finally {
typeStack.Remove(type);
}
}