protected override TypeVariableReference ComputeTypeToUnifyWith(VariableReference inputFacadeVariable, out bool setExpectedMutable)
{
setExpectedMutable = false;
TypeVariableReference other = inputFacadeVariable.TypeVariableReference;
TypeVariableReference u, l;
bool otherIsMutableReference;
bool otherIsReference = TypeVariableSet.TryDecomposeReferenceType(other, out u, out l, out otherIsMutableReference);
TypeVariableReference underlyingType = otherIsReference ? u : other;
NIType literalType;
bool underlyingTypeIsLiteral = TypeVariableSet.TryGetLiteralType(underlyingType, out literalType);
bool inputCoercesToStringSlice = underlyingTypeIsLiteral &&
(literalType == PFTypes.String || literalType == DataTypes.StringSliceType);
bool needsBorrow = !otherIsReference || !underlyingTypeIsLiteral || literalType != DataTypes.StringSliceType;
TypeVariableReference lifetimeType = otherIsReference
? l
: TypeVariableSet.CreateReferenceToLifetimeType(_group.BorrowLifetime);
if (needsBorrow)
{
_stringToSliceNeeded = true;
_group.SetBorrowRequired(false);
}
// If the input is allowed to coerce to a str, we can unify with str;
// otherwise, unify with the underlying type to get a type mismatch.
TypeVariableReference toUnifyUnderlyingType = inputCoercesToStringSlice
? TypeVariableSet.CreateReferenceToLiteralType(DataTypes.StringSliceType)
: underlyingType;
return(TypeVariableSet.CreateReferenceToReferenceType(
false,
toUnifyUnderlyingType,
lifetimeType));
}
protected override TypeVariableReference ComputeTypeToUnifyWith(VariableReference inputFacadeVariable, out bool setExpectedMutable)
{
TypeVariableReference other = inputFacadeVariable.TypeVariableReference;
TypeVariableReference u, otherReferenceLifetime;
bool otherIsMutableReference;
bool otherIsReference = TypeVariableSet.TryDecomposeReferenceType(other, out u, out otherReferenceLifetime, out otherIsMutableReference);
TypeVariableReference underlyingType = otherIsReference ? u : other;
bool mutable = otherIsReference ? otherIsMutableReference : inputFacadeVariable.Mutable;
TypeVariableReference typeToUnifyWith = default(TypeVariableReference);
setExpectedMutable = false;
switch (_mutability)
{
case InputReferenceMutability.RequireMutable:
{
TypeVariableReference lifetimeType;
if (!otherIsReference)
{
_group.SetBorrowRequired(true);
lifetimeType = TypeVariableSet.CreateReferenceToLifetimeType(_group.BorrowLifetime);
}
else
{
lifetimeType = otherReferenceLifetime;
}
typeToUnifyWith = TypeVariableSet.CreateReferenceToReferenceType(true, underlyingType, lifetimeType);
setExpectedMutable = !mutable;
break;
}
case InputReferenceMutability.AllowImmutable:
{
bool needsBorrow = !(otherIsReference && !otherIsMutableReference);
TypeVariableReference lifetimeType;
if (needsBorrow)
{
lifetimeType = TypeVariableSet.CreateReferenceToLifetimeType(_group.BorrowLifetime);
_group.SetBorrowRequired(false);
}
else
{
lifetimeType = otherReferenceLifetime;
}
typeToUnifyWith = TypeVariableSet.CreateReferenceToReferenceType(false, underlyingType, lifetimeType);
break;
}
case InputReferenceMutability.Polymorphic:
{
TypeVariableReference lifetimeType;
if (!otherIsReference)
{
_group.SetBorrowRequired(false /* TODO depends on current state and input mutability */);
lifetimeType = TypeVariableSet.CreateReferenceToLifetimeType(_group.BorrowLifetime);
}
else
{
// TODO: if TrueVariable.TypeVariableReference is already known to be immutable and
// wire reference is mutable, then we need a borrow
lifetimeType = otherReferenceLifetime;
}
typeToUnifyWith = TypeVariableSet.CreateReferenceToReferenceType(mutable, underlyingType, lifetimeType);
break;
}
}
return(typeToUnifyWith);
}