/// <summary>
/// User-defined conversions
/// </summary>
public static Expression UserDefinedConversion(ResolveContext ec, Expression source,
TypeSpec target, Location loc,
bool look_for_explicit, bool return_convert)
{
TypeSpec source_type = source.Type;
MethodSpec method = null;
Expression expr = null;
object o;
DoubleHash hash;
if (look_for_explicit) {
hash = explicit_conv;
} else {
// Implicit user operators cannot convert to interfaces
if (target.IsInterface)
return null;
hash = implicit_conv;
}
if (!(source is Constant) && hash.Lookup (source_type, target, out o)) {
method = (MethodSpec) o;
} else {
if (source_type == InternalType.Dynamic)
return null;
method = GetConversionOperator (ec.Compiler, null, source, target, look_for_explicit);
}
if (method != null) {
TypeSpec most_specific_source = method.Parameters.Types[0];
//
// This will do the conversion to the best match that we
// found. Now we need to perform an implict standard conversion
// if the best match was not the type that we were requested
// by target.
//
if (look_for_explicit) {
ReportPrinter temp = new SessionReportPrinter ();
ReportPrinter prev = ec.Report.SetPrinter (temp);
expr = ExplicitConversionStandard (ec, source, most_specific_source, loc);
ec.Report.SetPrinter (prev);
if (temp.ErrorsCount != 0)
expr = null;
} else {
if (ImplicitStandardConversionExists (source, most_specific_source))
expr = ImplicitConversionStandard (ec, source, most_specific_source, loc);
else
expr = null;
}
}
if (expr == null) {
bool nullable = false;
if (TypeManager.IsNullableType (source_type)) {
source = Nullable.Unwrap.Create (source);
nullable = true;
}
TypeSpec target_underlying;
if (TypeManager.IsNullableType (target)) {
target_underlying = TypeManager.GetTypeArguments (target)[0];
nullable = true;
} else {
// No implicit conversion S? -> T for non-reference type T
if (!look_for_explicit && !TypeManager.IsReferenceType (target))
nullable = false;
target_underlying = target;
}
if (nullable) {
expr = UserDefinedConversion (ec, source, target_underlying, loc, look_for_explicit, return_convert);
// Do result expression lifting only when it's needed
if (expr != null && (!look_for_explicit || TypeManager.IsReferenceType (target)))
expr = new Nullable.Lifted (expr, source, target).Resolve (ec);
return expr;
}
} else {
expr = new UserCast (method, expr, loc).Resolve (ec);
if (return_convert && !TypeManager.IsEqual (expr.Type, target)) {
if (look_for_explicit) {
expr = ExplicitConversionStandard (ec, expr, target, loc);
} else {
expr = ImplicitConversionStandard (ec, expr, target, loc);
}
}
}
if (!(source is Constant))
hash.Insert (source_type, target, method);
return expr;
}
//
// User-defined conversions
//
static Expression UserDefinedConversion (ResolveContext ec, Expression source, TypeSpec target, bool implicitOnly, Location loc)
{
List<MethodSpec> candidates = null;
//
// If S or T are nullable types, source_type and target_type are their underlying types
// otherwise source_type and target_type are equal to S and T respectively.
//
TypeSpec source_type = source.Type;
TypeSpec target_type = target;
Expression source_type_expr;
if (source_type.IsNullableType) {
// No implicit conversion S? -> T for non-reference types
if (implicitOnly && !TypeSpec.IsReferenceType (target_type) && !target_type.IsNullableType)
return null;
source_type_expr = Nullable.Unwrap.Create (source);
source_type = source_type_expr.Type;
} else {
source_type_expr = source;
}
if (target_type.IsNullableType)
target_type = Nullable.NullableInfo.GetUnderlyingType (target_type);
// Only these containers can contain a user defined implicit or explicit operators
const MemberKind user_conversion_kinds = MemberKind.Class | MemberKind.Struct | MemberKind.TypeParameter;
if ((source_type.Kind & user_conversion_kinds) != 0 && source_type.BuiltinType != BuiltinTypeSpec.Type.Decimal) {
bool declared_only = source_type.IsStruct;
var operators = MemberCache.GetUserOperator (source_type, Operator.OpType.Implicit, declared_only);
if (operators != null) {
FindApplicableUserDefinedConversionOperators (operators, source_type_expr, target_type, implicitOnly, ref candidates);
}
if (!implicitOnly) {
operators = MemberCache.GetUserOperator (source_type, Operator.OpType.Explicit, declared_only);
if (operators != null) {
FindApplicableUserDefinedConversionOperators (operators, source_type_expr, target_type, false, ref candidates);
}
}
}
if ((target.Kind & user_conversion_kinds) != 0 && target_type.BuiltinType != BuiltinTypeSpec.Type.Decimal) {
bool declared_only = target.IsStruct || implicitOnly;
var operators = MemberCache.GetUserOperator (target_type, Operator.OpType.Implicit, declared_only);
if (operators != null) {
FindApplicableUserDefinedConversionOperators (operators, source_type_expr, target_type, implicitOnly, ref candidates);
}
if (!implicitOnly) {
operators = MemberCache.GetUserOperator (target_type, Operator.OpType.Explicit, declared_only);
if (operators != null) {
FindApplicableUserDefinedConversionOperators (operators, source_type_expr, target_type, false, ref candidates);
}
}
}
if (candidates == null)
return null;
//
// Find the most specific conversion operator
//
MethodSpec most_specific_operator;
TypeSpec s_x, t_x;
if (candidates.Count == 1) {
most_specific_operator = candidates[0];
s_x = most_specific_operator.Parameters.Types[0];
t_x = most_specific_operator.ReturnType;
} else {
//
// Pass original source type to find the best match against input type and
// not the unwrapped expression
//
s_x = FindMostSpecificSource (candidates, source.Type, source_type_expr, !implicitOnly);
if (s_x == null)
return null;
t_x = FindMostSpecificTarget (candidates, target, !implicitOnly);
if (t_x == null)
return null;
most_specific_operator = null;
for (int i = 0; i < candidates.Count; ++i) {
if (candidates[i].ReturnType == t_x && candidates[i].Parameters.Types[0] == s_x) {
most_specific_operator = candidates[i];
break;
}
}
if (most_specific_operator == null) {
MethodSpec ambig_arg = null;
foreach (var candidate in candidates) {
if (candidate.ReturnType == t_x)
most_specific_operator = candidate;
else if (candidate.Parameters.Types[0] == s_x)
ambig_arg = candidate;
}
ec.Report.Error (457, loc,
"Ambiguous user defined operators `{0}' and `{1}' when converting from `{2}' to `{3}'",
ambig_arg.GetSignatureForError (), most_specific_operator.GetSignatureForError (),
source.Type.GetSignatureForError (), target.GetSignatureForError ());
return ErrorExpression.Instance;
}
}
//
// Convert input type when it's different to best operator argument
//
if (s_x != source_type) {
var c = source as Constant;
if (c != null) {
source = c.TryReduce (ec, s_x, loc);
} else {
source = implicitOnly ?
ImplicitConversionStandard (ec, source_type_expr, s_x, loc) :
ExplicitConversionStandard (ec, source_type_expr, s_x, loc);
}
} else {
source = source_type_expr;
}
source = new UserCast (most_specific_operator, source, loc).Resolve (ec);
//
// Convert result type when it's different to best operator return type
//
if (t_x != target_type) {
//
// User operator is of T?, no need to lift it
//
if (t_x == target && t_x.IsNullableType)
return source;
source = implicitOnly ?
ImplicitConversionStandard (ec, source, target_type, loc) :
ExplicitConversionStandard (ec, source, target_type, loc);
if (source == null)
return null;
}
//
// Source expression is of nullable type, lift the result in the case it's null and
// not nullable/lifted user operator is used
//
if (source_type_expr is Nullable.Unwrap && !s_x.IsNullableType && (TypeSpec.IsReferenceType (target) || target_type != target))
source = new Nullable.Lifted (source, source_type_expr, target).Resolve (ec);
else if (target_type != target)
source = Nullable.Wrap.Create (source, target);
return source;
}
//
// User-defined conversions
//
static Expression UserDefinedConversion (ResolveContext ec, Expression source, TypeSpec target, bool implicitOnly, Location loc)
{
List<MethodSpec> candidates = null;
//
// If S or T are nullable types, S0 and T0 are their underlying types
// otherwise S0 and T0 are equal to S and T respectively.
//
TypeSpec source_type = source.Type;
TypeSpec target_type = target;
Expression unwrap;
if (TypeManager.IsNullableType (source_type)) {
// No implicit conversion S? -> T for non-reference types
if (implicitOnly && !TypeManager.IsReferenceType (target_type) && !TypeManager.IsNullableType (target_type))
return null;
unwrap = source = Nullable.Unwrap.Create (source);
source_type = source.Type;
} else {
unwrap = null;
}
if (TypeManager.IsNullableType (target_type))
target_type = Nullable.NullableInfo.GetUnderlyingType (target_type);
// Only these containers can contain a user defined implicit or explicit operators
const MemberKind user_conversion_kinds = MemberKind.Class | MemberKind.Struct | MemberKind.TypeParameter;
if ((source_type.Kind & user_conversion_kinds) != 0 && source_type != TypeManager.decimal_type) {
bool declared_only = source_type.IsStruct;
var operators = MemberCache.GetUserOperator (source_type, Operator.OpType.Implicit, declared_only);
if (operators != null) {
FindApplicableUserDefinedConversionOperators (operators, source, target_type, implicitOnly, ref candidates);
}
if (!implicitOnly) {
operators = MemberCache.GetUserOperator (source_type, Operator.OpType.Explicit, declared_only);
if (operators != null) {
FindApplicableUserDefinedConversionOperators (operators, source, target_type, false, ref candidates);
}
}
}
if ((target.Kind & user_conversion_kinds) != 0 && target != TypeManager.decimal_type) {
bool declared_only = target.IsStruct || implicitOnly;
var operators = MemberCache.GetUserOperator (target_type, Operator.OpType.Implicit, declared_only);
if (operators != null) {
FindApplicableUserDefinedConversionOperators (operators, source, target_type, implicitOnly, ref candidates);
}
if (!implicitOnly) {
operators = MemberCache.GetUserOperator (target_type, Operator.OpType.Explicit, declared_only);
if (operators != null) {
FindApplicableUserDefinedConversionOperators (operators, source, target_type, false, ref candidates);
}
}
}
if (candidates == null)
return null;
//
// Find the most specific conversion operator
//
MethodSpec most_specific_operator;
TypeSpec s_x, t_x;
if (candidates.Count == 1) {
most_specific_operator = candidates[0];
s_x = most_specific_operator.Parameters.Types[0];
t_x = most_specific_operator.ReturnType;
} else {
s_x = FindMostSpecificSource (candidates, source, !implicitOnly);
if (s_x == null)
return null;
t_x = FindMostSpecificTarget (candidates, target, !implicitOnly);
if (t_x == null)
return null;
most_specific_operator = candidates[0];
for (int i = 1; i < candidates.Count; ++i) {
if (candidates[i].ReturnType == t_x && candidates[i].Parameters.Types[0] == s_x) {
most_specific_operator = candidates[i];
break;
}
}
}
//
// Convert input type when it's different to best operator argument
//
if (s_x != source.Type)
source = implicitOnly ?
ImplicitConversionStandard (ec, source, s_x, loc) :
ExplicitConversionStandard (ec, source, s_x, loc);
source = new UserCast (most_specific_operator, source, loc).Resolve (ec);
//
// Convert result type when it's different to best operator return type
//
if (t_x != target_type) {
//
// User operator is of T?, no need to lift it
//
if (TypeManager.IsNullableType (t_x) && t_x == target)
return source;
source = implicitOnly ?
ImplicitConversionStandard (ec, source, target_type, loc) :
ExplicitConversionStandard (ec, source, target_type, loc);
}
//
// Source expression is of nullable type, lift the result in case of it's null
//
if (unwrap != null && (TypeManager.IsReferenceType (target) || target_type != target))
source = new Nullable.Lifted (source, unwrap, target).Resolve (ec);
else if (target_type != target)
source = Nullable.Wrap.Create (source, target);
return source;
}
